Playing with the idea of what it will take to rebuild a type 4 pump.
The pump that came out of my 2.0L engine is trashed from pumping rust. Both the gears and the housings are seriously scored.
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I figured I'd roll the dice and see what might be on Ebay. Took a gamble and bought a used pump hoping I might get some core parts that are useful.
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I did end up with a good housing outer. However, the gears are pitted and it the inner housing plate either has a serious casting flaw, or some sort of galvanic corrosion that pitted it. I always struggle with this kind of thing. It really would have minimal effect on the pump and it probably worked OK for a lot of years. However, I'd just like to know that it is perfect going before going into a engine.
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It looks like new inner plates are available but at a cost of $150+.
I decided that since I have a donor "scrap" pump, I have nothing to lose by experimenting with machining it.
Full Version: Type 4 oil pump rebuild
Personally I'd use a new modified T1 pump and a steel cover. 
I decided to start with my original pump inner housing since that was in better shape.
On the original it had some light scoring and the stationary shaft had been pushed out toward the cam and actually had been lightly brushing the cam bolts.
No harm in messing with this one. Disassembled for machine work.
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Setup in the lathe for a light skim cut.
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The idea here was to just do a light skim cut of 0.001 - 0.002" to clean up the scoring.
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On the original it had some light scoring and the stationary shaft had been pushed out toward the cam and actually had been lightly brushing the cam bolts.
No harm in messing with this one. Disassembled for machine work.
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Setup in the lathe for a light skim cut.
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The idea here was to just do a light skim cut of 0.001 - 0.002" to clean up the scoring.
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QUOTE(Mark Henry @ May 26 2019, 07:59 PM) 
Personally I'd use a new modified T1 pump and a steel cover.
I looked at that option. Seems to simple.
I really would like to keep type 4 pump. I'm an engineer - I basically look at things from the perspective of why wouldn't VW have used a type 1 pump in the 1st place if it was up to the task.
Don't want a 30mm Type 1 pump. I couldn't seem to find a 26mm modified type 1 pump. It also seems that previous threads on this site and others indicated that type 1 pumps are having some issues sealing properly to the case. Maybe I'm mistaken.
Has the leakage situation changed?
Open to a good source for such a 26mm type 1 pump and don't want to negate anyone's prior experience if they are using Type 1 pumps and happy with them.
I really don't want to deal with band aids if I can avoid them. Part of my goal is to keep my 2.0L engine stock. But, I admit I'm working on my own Band Aid.
Plus I needed a reason to play with machine tools on this holiday weekend!
I bought a new Melling pump. Made in Michigan from what I've been able to determine, Its a high flow pump and is a bit thicker than stock. Runs a thinnnnnnn gasket as a result. Make sure your case is flat in the area where the gasket needs to seal. Had to take the engine out to redo the seal. Great oil pressure. $90 bucks IIRC
So here is the cover with just a skim cut and the shaft reassembled to suit the new Ebay housing.
The light score that is can barely be felt and will not cause any issues if I decide to use this part. Plus, it likely can be lapped out before I do any final assembly.
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Here is the new depth of the stationary shaft. It is probably a good 3/16" deeper than where it started - gives an idea of just how far these shafts can be pushed out by hydraulic pressure if the engine is overheated.
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Ultimately I will pin this shaft to the housing plate to prevent it from moving. We'll see if I can get to that tomorrow.
Here is a comparison of the machined plate vs. the Ebay flawed plate.
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The light score that is can barely be felt and will not cause any issues if I decide to use this part. Plus, it likely can be lapped out before I do any final assembly.
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Here is the new depth of the stationary shaft. It is probably a good 3/16" deeper than where it started - gives an idea of just how far these shafts can be pushed out by hydraulic pressure if the engine is overheated.
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Ultimately I will pin this shaft to the housing plate to prevent it from moving. We'll see if I can get to that tomorrow.
Here is a comparison of the machined plate vs. the Ebay flawed plate.
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QUOTE(North Coast Jim @ May 26 2019, 08:10 PM)
I bought a new Melling pump. Made in Michigan from what I've been able to determine, Its a high flow pump and is a bit thicker than stock. Runs a thinnnnnnn gasket as a result. Make sure your case is flat in the area where the gasket needs to seal. Had to take the engine out to redo the seal. Great oil pressure. $90 bucks IIRC
I've considered the Melling. Not convinced the cast iron pump in an aluminum case is the best way to go. However, of the options I've found so far a T4 rebuild actually seems most appealing as a direct fit replacement.
Ultimately I may machine up some sort of test fixture to see if I can convince myself that a rebuilt pump is indeed viable.
Still scratching my head on how to best determine what the head pressure is of the engine oiling circuit. May just have to put a valve in the system and then tune it to match typical cold start oil pressures.
Seems crazy to me that Type 4 pumps are No Longer Available and those pieces that you can find are astronomical in price. Something like $400 for an outer housing, $150 for the inner housing plate. The driven gear is also NLA.
Porsche pisses me off with this nonsense.
They love to claim that 70% of Porsche's are still on the road yet do very little to enable those of us trying to keep them on the road. Thanks for nothing while taking the credit for the work owners go to, just to find a way to work around Porsche! Typical Corporate double speak.
https://www.porsche.com/international/acces...ervice/classic/
Still scratching my head on how to best determine what the head pressure is of the engine oiling circuit. May just have to put a valve in the system and then tune it to match typical cold start oil pressures.
Seems crazy to me that Type 4 pumps are No Longer Available and those pieces that you can find are astronomical in price. Something like $400 for an outer housing, $150 for the inner housing plate. The driven gear is also NLA.
Porsche pisses me off with this nonsense.
They love to claim that 70% of Porsche's are still on the road yet do very little to enable those of us trying to keep them on the road. Thanks for nothing while taking the credit for the work owners go to, just to find a way to work around Porsche! Typical Corporate double speak. https://www.porsche.com/international/acces...ervice/classic/
Number 1 reason for failing oil pumps is the idle axle getting loose and backing out into the camshaft.
Make sure that axle is well fixated.
All the other wear I see there is not nice, will cause some efficiency loss but won't really fail the pump unless really bad or the gears start having axial play.
Make sure that axle is well fixated.
All the other wear I see there is not nice, will cause some efficiency loss but won't really fail the pump unless really bad or the gears start having axial play.
QUOTE(Valy @ May 26 2019, 11:40 PM)
Number 1 reason for failing oil pumps is the idle axle getting loose and backing out into the camshaft.
Make sure that axle is well fixated.
All the other wear I see there is not nice, will cause some efficiency loss but won't really fail the pump unless really bad or the gears start having axial play.
@valy
Nice engine build thread! Hadn't seen it before.
How many miles do you have on your type 1 pump now? Any issues with leakage or higher oil temps?
Type 1 is tempting.
@North_Coast_Jim
How many miles on the melling? Any issues with leaks or oil temp?
How many miles on the melling? Any issues with leaks or oil temp?
QUOTE(Superhawk996 @ May 27 2019, 06:50 AM)
@North_Coast_Jim
How many miles on the melling? Any issues with leaks or oil temp?
Its a recent rebuild 2 years ago. Builder recommended the pump as he puts them into all his type IV builds. He has done rebuilds for years including some SCCA and IMSA cars back in the day. 40 years experience.
Only issue with the Melling pump so far is the very then gasket. Tore the gasket on initial install and had to pull the engine to fix. Presently I do have a small leak at the junction of the case halves and the pump. Not enough to cause me concern but one day ………..
Excellent oil pressure and flow. No over heat conditions are seen. Engine has about 2000 miles on it still rebuild.
@Superhawk996
It works well, no issues so far but I'm not driving it much.
Just make sure you get a pump that has the right diameter.
The iron ones like Melling are too small and expand at a different rate than aluminum. Even with the O ring, there will be a lot of bypass between in and out and a lot of pressure on the outside gasket that may eventually fail.
Make sure the mounting surface is flat (the 2 case halfs) and always add some sealer to the gasket. Use a thick gasket too. Look at the gasket template in my signature. I made my own gaskets to be sure.
Don't over torque the bolts if you don't want leaks and use big washers.
It works well, no issues so far but I'm not driving it much.
Just make sure you get a pump that has the right diameter.
The iron ones like Melling are too small and expand at a different rate than aluminum. Even with the O ring, there will be a lot of bypass between in and out and a lot of pressure on the outside gasket that may eventually fail.
Make sure the mounting surface is flat (the 2 case halfs) and always add some sealer to the gasket. Use a thick gasket too. Look at the gasket template in my signature. I made my own gaskets to be sure.
Don't over torque the bolts if you don't want leaks and use big washers.
There is a thread over on the Samba with a step by step instruction about rebuilding and blueprinting a Type 4 oil pump. Look for the posting in the 411/412 car section entitled “Rebuilding a 1.8L 412 motor”
T1 mod is easy if you have a lathe, you just have to cut the nose down to clear the cam bolts.
I have lots of miles on mine and I've done it to many customers builds. I use the Shadeck 26mm always a steel cover., just did one with a 30mm and GB pressure relief cover.
I have lots of miles on mine and I've done it to many customers builds. I use the Shadeck 26mm always a steel cover., just did one with a 30mm and GB pressure relief cover.
Given that I'm a mechanical masochist I haven't given up on the Type 4 Pumps.
In fact, I've begun collecting them.
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Previous Roll call:
1) from my original engine - pump is garbage. Heavily scored from pumping rust.
2) E-bay purchase. Pitted gears and a housing plate that has a defect or corrosion.
3) Pump from GA000099 engine - In great shape and reusable.
But I still need a good pump for my original engine. I haven't given up on the machining of the housing plate and pinning the shaft. In fact, I will pin the shafts of both engines regardless.
But rather than get deep in the machine work at the moment, I purchased two more pumps here on the forum to see if I could find more good parts to mix and match a 2nd good pump.
So I opened up the dirty pump first -- This is like Christmas for me. I love to see what is in the box for the 1st time.
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And what a great Christmas it was. Another usable pump in great condition.
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Only the lightest of scoring on the gears and the housings. Perfect to reuse after I pin the shaft.
The second pump is a bit of a mystery.
On 1st inspection, it's clear that something isn't quite right. the stationary gear shaft is sitting far too deep in the housing plate.
For the record - I have no issue with the seller on this. If you're not familiar with these pumps it would be easy to miss. Plus as always, you never quite know what you'll actually get and I didn't ask any questions since the price wasn't a concern. This was intended as a parts grab bag anyway on my part.
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Opening up the pump was a mixed bag. The external housing is in awesome shape. and is immaculately clean. I think it was probably vapor blasted. it is that nice.
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I will need to do a little measuring just to make sure the gap between the gears and pump bore is right but this part looks unused and amazing visually.
The internals are a mystery. I think the gears are 24mm Type 1 gears. They are in great shape & look brand new.
However, what is clear is that the shafts (both driven & stationary) aren't Type 4. They are definitely too short. I suspect Type 1 but really don't know enough about the Type 1 to be sure.
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However, this is sort of a blessing in disguise. I hadn't considered the possibility of being able to swap a new gear onto the driven shaft.
Now I have new toys to play with.
I suspect what I'll do is mix and match enough parts to produce another good 3rd pump using the immaculate housing, a machined housing plate, and probably some swapping around of gears.
The gears that I think are Type 1 seem to measure exactly the same as Type 4 gears for both OD and height. I need to do a better comparison of the tooth profile but it really wouldn't matter as long as they are kept as a pair.
New science project work ahead.
With 5 pumps on hand and two ready for use, this Oil pump rebuild project will likely get shelved for a bit other than a quick update later on when I finally pin the shafts of the two pumps I'm going to use for rebuild of GA000099 and my original engine.
In fact, I've begun collecting them.
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Previous Roll call:
1) from my original engine - pump is garbage. Heavily scored from pumping rust.
2) E-bay purchase. Pitted gears and a housing plate that has a defect or corrosion.
3) Pump from GA000099 engine - In great shape and reusable.
But I still need a good pump for my original engine. I haven't given up on the machining of the housing plate and pinning the shaft. In fact, I will pin the shafts of both engines regardless.
But rather than get deep in the machine work at the moment, I purchased two more pumps here on the forum to see if I could find more good parts to mix and match a 2nd good pump.
So I opened up the dirty pump first -- This is like Christmas for me. I love to see what is in the box for the 1st time.
Click to view attachment
And what a great Christmas it was. Another usable pump in great condition.
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Only the lightest of scoring on the gears and the housings. Perfect to reuse after I pin the shaft.
The second pump is a bit of a mystery.
On 1st inspection, it's clear that something isn't quite right. the stationary gear shaft is sitting far too deep in the housing plate.
For the record - I have no issue with the seller on this. If you're not familiar with these pumps it would be easy to miss. Plus as always, you never quite know what you'll actually get and I didn't ask any questions since the price wasn't a concern. This was intended as a parts grab bag anyway on my part.
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Opening up the pump was a mixed bag. The external housing is in awesome shape. and is immaculately clean. I think it was probably vapor blasted. it is that nice.
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I will need to do a little measuring just to make sure the gap between the gears and pump bore is right but this part looks unused and amazing visually.
The internals are a mystery. I think the gears are 24mm Type 1 gears. They are in great shape & look brand new.
However, what is clear is that the shafts (both driven & stationary) aren't Type 4. They are definitely too short. I suspect Type 1 but really don't know enough about the Type 1 to be sure.
Click to view attachment
However, this is sort of a blessing in disguise. I hadn't considered the possibility of being able to swap a new gear onto the driven shaft.
Now I have new toys to play with.
I suspect what I'll do is mix and match enough parts to produce another good 3rd pump using the immaculate housing, a machined housing plate, and probably some swapping around of gears.
The gears that I think are Type 1 seem to measure exactly the same as Type 4 gears for both OD and height. I need to do a better comparison of the tooth profile but it really wouldn't matter as long as they are kept as a pair.
New science project work ahead.
With 5 pumps on hand and two ready for use, this Oil pump rebuild project will likely get shelved for a bit other than a quick update later on when I finally pin the shafts of the two pumps I'm going to use for rebuild of GA000099 and my original engine.
Try visiting The Samba.com website and go to the 411/412 Forum section. There is a thread on rebuilding a 1.8L 411 motor that goes into a terrifically detailed explanation of rebuilding and blueprinting the Type 4 oil pump.
Been there before.
https://www.thesamba.com/vw/forum/viewtopic.php?t=699156
I will definitely use the site as a reference. It has great information and some useful techniques and I really like his gear locking fixture.
"Blueprinting" is overkill in the sense that I'm not looking for perfectly lapped surfaces.
Don't get me wrong, blueprinting has it's place on race engines and other really high dollar machinery that runs at high RPM.
Even when these Type 4 pumps were new, there are machine tool marks evident in both housings as well as on the gear ends. There is sufficient overcapacity built into all mass produced oil pumps to account for these manufacturing imperfections.
Likewise all manufactured components have a tolerance from nominal. Without the actual part blueprint (or CAD in modern manufacture) there is no blueprinting going on in the sense that the part is being brought to nominal dimension, balance, surface finish, etc.
So for my purposes, I'm mainly interested in obtaining fully functional, durable, and usable parts without being overly concerned about "blueprinting" and having highly lapped surfaces.
Again, to be clear - I'm not talking down that Samba post, and, thank your for originally posting it. It is a great resource.
What I am very interested in is building up a means to test and compare pumps though to ensure that on any pump that gets mix & matched parts ends up fully functional and that functionality can be proven.
I have some ideas on this test fixture -- I'll post as it evolves.
I've had one listed on FS/WTB for a couple of weeks. It's still there, as far as I know Brand new, never used. Asking $50 plus shipping.
Time to light up an old thread. I continue to build my Type 4 oil pump collection with the firm belief that the Type 4 oil pump is the way to go for a Type 4 engine.
A while back I acquired one of the CNC Type 4 pumps that was offered on the Samba. I'm finally going to get around to posting a comparion to the OEM pump. In addition, I'll compare it (later on in a separate post to this thread) to a mystery type 4 pump that demonstrates why you want to open up a T4 pump before you use it blindly.
As mentioned previously my final intent is to build a fixture that will let me objectively evaluate T4 pump pressure vs. volume curves. This is still a long ways off since I'll need to machine a fixture as well as buy a flow meter which can get pricy.
Anyway . . . . here we go.
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The Samba pump is very nicely done. The main problem I ran into with it is that I thought it would be a duplicate of the OEM pump. It is almost perfectly close in all regards except one. The gear set is 30mm. Doh!
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vs. OEM 24mm gearset.
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Both gears are the same diameter.
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This can be a pro or a con depending on intended use. It will be great for an external oil cooler setup. Otherwise, it will be pumping more oil and sapping more horsepower to drive than the OEM pump. It can be argued that the increased flow will provide better oil pressure when hot, but, there is also such a thing as too much oil pressure. I'll set that aside for now.
You'll notice the housing face plate for the Samba pump is different than the OEM pump in order to accomodate the 30mm gear set. The OEM face plate is flat. The Samba pump has been counterbored in order to fit the 30mm gear into the same space. All machine work on the Samba pump appears to top notch but I haven't done a deep dive on clearance between the pump gears and the pump housing. For the moment, I'm assuming that since it is CNC'd its good. It certainly looks good.
I also notice that the driven shaft is recessed deeper in the driven gear.
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Looking at the amount of engagement that the idler shat has with the housing. It is about the same as OEM.
OEM is 6.76mm
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Samba is 6.33mm
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For me, the fact that the idler gear is in double shear is a big plus for the T4 pump.
Of course the major design flaw with the T4 oil pump is the fact that the idler shaft isn't pinned into the face plate. If the engine is overheated, the difference in thermal expansion between aluminum and steel can create the opportunity for the idler shaft to get pushed outward in the housing toward the cam gear. The easy fix is to pin the idler shaft. This should be done with any reused T4 pump and would also need to be done with the Samba pump.
Here is the comparison of the OEM housing to the Samba housing.
OEM
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Samba
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And finally, here is a comparion of the exterior of the pumps.
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A while back I acquired one of the CNC Type 4 pumps that was offered on the Samba. I'm finally going to get around to posting a comparion to the OEM pump. In addition, I'll compare it (later on in a separate post to this thread) to a mystery type 4 pump that demonstrates why you want to open up a T4 pump before you use it blindly.
As mentioned previously my final intent is to build a fixture that will let me objectively evaluate T4 pump pressure vs. volume curves. This is still a long ways off since I'll need to machine a fixture as well as buy a flow meter which can get pricy.
Anyway . . . . here we go.
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The Samba pump is very nicely done. The main problem I ran into with it is that I thought it would be a duplicate of the OEM pump. It is almost perfectly close in all regards except one. The gear set is 30mm. Doh!
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vs. OEM 24mm gearset.
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Both gears are the same diameter.
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This can be a pro or a con depending on intended use. It will be great for an external oil cooler setup. Otherwise, it will be pumping more oil and sapping more horsepower to drive than the OEM pump. It can be argued that the increased flow will provide better oil pressure when hot, but, there is also such a thing as too much oil pressure. I'll set that aside for now.
You'll notice the housing face plate for the Samba pump is different than the OEM pump in order to accomodate the 30mm gear set. The OEM face plate is flat. The Samba pump has been counterbored in order to fit the 30mm gear into the same space. All machine work on the Samba pump appears to top notch but I haven't done a deep dive on clearance between the pump gears and the pump housing. For the moment, I'm assuming that since it is CNC'd its good. It certainly looks good.
I also notice that the driven shaft is recessed deeper in the driven gear.
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Looking at the amount of engagement that the idler shat has with the housing. It is about the same as OEM.
OEM is 6.76mm
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Samba is 6.33mm
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For me, the fact that the idler gear is in double shear is a big plus for the T4 pump.
Of course the major design flaw with the T4 oil pump is the fact that the idler shaft isn't pinned into the face plate. If the engine is overheated, the difference in thermal expansion between aluminum and steel can create the opportunity for the idler shaft to get pushed outward in the housing toward the cam gear. The easy fix is to pin the idler shaft. This should be done with any reused T4 pump and would also need to be done with the Samba pump.
Here is the comparison of the OEM housing to the Samba housing.
OEM
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Samba
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And finally, here is a comparion of the exterior of the pumps.
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Used T4 mystery pump.
Heres a caution to anyone buying a used T4 pump for resue. You need to open them up and make sure it has the right parts inside before you use it.
I do want to note that I've bought several pumps off the forum here as well as e-bay for cores and to understand the variance in these pumps. I don't hold anyone at fault for a pump that isn't 100% OEM. That is a chance you take collecting core pumps.
Previously in this thread I ran across a pump that appears to have been rebuilt with non-OEM parts. I suspect that across 50 years in service, folks have decided to swap in T1 parts occasionally.
We'll here is another case study.
First clue is that the idler shaft is sitting way too deep in the face plate housing. OEM pump from GA000099 on the right for comparison.
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Likewise, on the inside of the pump, there isn't enough of the idler shaft exposed to engage with the housing counterbore properly. The engagement would only be about 3mm where as the OEM pump is about 6.7mm.
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When I took this pump apart, it was clear that someone had been inside before me. The washers under the nuts on the OEM pumps are a very thin wave washer. On this pump, they were conventional washers.
It seems to be that this is either a misbuild of the pump at the factory or someone has swapped in an idler shaft from some thing other than a T4 pump. I suspect T1, because so many of the guys that played with T4 engines back in the day also played with the VW T1's from the Bug too. Well at least I did! Why would someone swap in a T1 idler shaft into a T4 pump? Your guess is as good as mine.
In the case of this mystery pump, it had some mild scoring of the pump body from pumping chunks and/or rust at some point. The comparion on the right is the pump housing from Engine GA000099 that was low mileage and had a pump in pretty good shape.
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I've seen worse, and this one (on left) is likely fine but the scoring of the housing and the gear set will reduce pump efficiency. How much is yet to be determined and is the reason I will eventually build a test setup to measure these pumps.
Here again is a comparison of the this gear set (left) with some scoring of the gear OD vs. GA000099 which is pretty free of scoring on the OD of the gear.
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Bottom line to all this. Before you try to resuse a used T4 pump, at least open it up and make sure what you have are the right OEM parts in there and that things aren't too torn up. And like any T4 pump, the idler shaft should be pinned to prevent movment.
Heres a caution to anyone buying a used T4 pump for resue. You need to open them up and make sure it has the right parts inside before you use it.
I do want to note that I've bought several pumps off the forum here as well as e-bay for cores and to understand the variance in these pumps. I don't hold anyone at fault for a pump that isn't 100% OEM. That is a chance you take collecting core pumps.
Previously in this thread I ran across a pump that appears to have been rebuilt with non-OEM parts. I suspect that across 50 years in service, folks have decided to swap in T1 parts occasionally.
We'll here is another case study.
First clue is that the idler shaft is sitting way too deep in the face plate housing. OEM pump from GA000099 on the right for comparison.
Click to view attachment
Likewise, on the inside of the pump, there isn't enough of the idler shaft exposed to engage with the housing counterbore properly. The engagement would only be about 3mm where as the OEM pump is about 6.7mm.
Click to view attachment
When I took this pump apart, it was clear that someone had been inside before me. The washers under the nuts on the OEM pumps are a very thin wave washer. On this pump, they were conventional washers.
It seems to be that this is either a misbuild of the pump at the factory or someone has swapped in an idler shaft from some thing other than a T4 pump. I suspect T1, because so many of the guys that played with T4 engines back in the day also played with the VW T1's from the Bug too. Well at least I did! Why would someone swap in a T1 idler shaft into a T4 pump?
Your guess is as good as mine. In the case of this mystery pump, it had some mild scoring of the pump body from pumping chunks and/or rust at some point. The comparion on the right is the pump housing from Engine GA000099 that was low mileage and had a pump in pretty good shape.
Click to view attachment
I've seen worse, and this one (on left) is likely fine but the scoring of the housing and the gear set will reduce pump efficiency. How much is yet to be determined and is the reason I will eventually build a test setup to measure these pumps.
Here again is a comparison of the this gear set (left) with some scoring of the gear OD vs. GA000099 which is pretty free of scoring on the OD of the gear.
Click to view attachment
Bottom line to all this. Before you try to resuse a used T4 pump, at least open it up and make sure what you have are the right OEM parts in there and that things aren't too torn up. And like any T4 pump, the idler shaft should be pinned to prevent movment.
T4 Mystery Pumps -- The plot thickens
Recently bought a couple more used T4 pumps for futher investigation.
One had an idler shaft that was recessed pretty deeply. The other (right) had an idler shaft that was peened as preventative measure to keep the shaft from moving.
I'm going to compare these to the low mile, OEM pump that came out of GA000099 (center) which shows virtually no wear and is the closest thing I have to a baseline of what the OEM pump should be.
Click to view attachment
On the pump (far left) with the deeply recessed idler shaft, this is the third I've seen this way. The other two, I belived to have been some sort of Type 1 pump parts swap. This was primarily because one of them clearly had a diferent set of pump gears vs. any others I've seen come out of a T4 pump to date.
The idler shaft has a slight protrusion behind the gear that sticks out. This is by design. It goes into the counter bore in the pump housing. This is the feature of the T4 pump that puts the idler gear into double shear vs. a Type 1 pump in single shear.
So after measuring all three pumps, it was very curious to me that all three pumps have EXACTLY 6.59mm of idler shaft protrusion behind the idler gear.
Click to view attachment
If someone had messed with the idler shaft and replaced it with a different (shorter) shaft, I'd expect some variation in this protrusion length. I saw that variation in one of the previous pumps. In that case, there was barely enough of the idler shaft sticking out to engage the counter bore.
Hmm. Now I'm starting to think that VW actually changed the T4 pumps somewhere along the way to address the possibility of the idler shaft getting pushed out into the cam gear. Anyone else have T4 pumps that you've seen with the deeply recessed idler shafts? If so please feel free to post info here to confirm or deny this possibility.
Otherwise, these two pumps look pretty resonable to what I'd expect from a used T4 pump. Some mild scoring of the main housings was evident from pumping some usual garbage. On the whole, both pumps should be completely serviceable after pinning the ider shafts. The one thing that I see as a downside to the short ider shafts is that it will be much more difficult to pin the idler shaft since there is less of it to work with w.r.t how much shaft is engaged in the housing.
The other curious thing about the pump on the left is that the driven gear has the drive shaft with the drive tang counter sunk to the end of the driven gear. In the past, when I've seen this I had assumed that it was the result of swapping in T1 parts. Now I'm not so sure.
As a couple final items of note, both these pumps had OEM washers and nuts unlike a couple of the earlier pumps. Sample size of T4 pumps is now 10 including the CNC Samba pump previously reviewed.
Recently bought a couple more used T4 pumps for futher investigation.
One had an idler shaft that was recessed pretty deeply. The other (right) had an idler shaft that was peened as preventative measure to keep the shaft from moving.
I'm going to compare these to the low mile, OEM pump that came out of GA000099 (center) which shows virtually no wear and is the closest thing I have to a baseline of what the OEM pump should be.
Click to view attachment
On the pump (far left) with the deeply recessed idler shaft, this is the third I've seen this way. The other two, I belived to have been some sort of Type 1 pump parts swap. This was primarily because one of them clearly had a diferent set of pump gears vs. any others I've seen come out of a T4 pump to date.
The idler shaft has a slight protrusion behind the gear that sticks out. This is by design. It goes into the counter bore in the pump housing. This is the feature of the T4 pump that puts the idler gear into double shear vs. a Type 1 pump in single shear.
So after measuring all three pumps, it was very curious to me that all three pumps have EXACTLY 6.59mm of idler shaft protrusion behind the idler gear.
Click to view attachment
If someone had messed with the idler shaft and replaced it with a different (shorter) shaft, I'd expect some variation in this protrusion length. I saw that variation in one of the previous pumps. In that case, there was barely enough of the idler shaft sticking out to engage the counter bore.
Hmm. Now I'm starting to think that VW actually changed the T4 pumps somewhere along the way to address the possibility of the idler shaft getting pushed out into the cam gear. Anyone else have T4 pumps that you've seen with the deeply recessed idler shafts? If so please feel free to post info here to confirm or deny this possibility. Otherwise, these two pumps look pretty resonable to what I'd expect from a used T4 pump. Some mild scoring of the main housings was evident from pumping some usual garbage. On the whole, both pumps should be completely serviceable after pinning the ider shafts. The one thing that I see as a downside to the short ider shafts is that it will be much more difficult to pin the idler shaft since there is less of it to work with w.r.t how much shaft is engaged in the housing.
The other curious thing about the pump on the left is that the driven gear has the drive shaft with the drive tang counter sunk to the end of the driven gear. In the past, when I've seen this I had assumed that it was the result of swapping in T1 parts. Now I'm not so sure.
As a couple final items of note, both these pumps had OEM washers and nuts unlike a couple of the earlier pumps. Sample size of T4 pumps is now 10 including the CNC Samba pump previously reviewed.
Another thing to keep an eye out for is the small nuts holding the housing together actually have threaded inserts from the factory (don't know if true of all years though?) that I believe act almost as lock nuts. I noticed that when doing my 1.7 rebuild for my VW and got that answer on my STF thread. (In sig) Might be another indicator of a pump being opened/worked on previously.
That CNC pump is pretty.
That CNC pump is pretty.
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