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Posted by: Valy Sep 15 2011, 09:38 PM

I'm rebuilding a 2.0L and posted a lot of pictures in a different thread.
One of the pictures showed the oil pump and Jake immediately noticed that the pump failed. Went back to the engine and saw how the oil pump touched the cam gear and shred off the nits holding it.




Being such an anal guy, I took same time today to understand why did the oil pump fail?



The red axle in the picture above it the one that protruded through the pump cover. There's nothing that holds it in place except the friction between it and the cover!
So Why does it move?
This red axle goes into a cavity of the oil pump case (rightmost in the figure). The cavity is almost snug-fit to the axle but oil can infiltrate around the axle into the cavity. When the pump works, there is a bit of oil pressure in the pump that causes the oil in the cavity to push the axle out; just like a hydraulic piston. The force is small but it's constantly there. As the axle moves, more oil flows in and that keeps pushing the axle out.
Over the time, that axle is pushed out of the pump cover until it starts touching the cam gear, shredding the nits that hold it. Eventually, the nits will brake or the axle will block the movement of the camshaft and something else will brake or your camshaft bearings will give due to the vibration inducted by the hits.

The aftermarket oil pumps are build differently, with no axle that can protrude into the motor, making them a good upgrade to your old original pump.

Make yourself a note to replace that old oil pump at the first occasion. I will even recommend to create that occasion before it's too late.

Posted by: jsconst Sep 15 2011, 09:53 PM

This may all be true, but aftermarket pumps from what I've been reading have their problems also, mainly quality control, too much clearance causing frothing of the oil. So what aftermarket pump and how do you know it will be better. Or last, haven't found much data to support me buying one for my rebuild yet. Have posed the question here and other forums with no real solutions offered.
Good luck if you find an acceptable replacement I would be interested in hearing about it.


Jeff

Posted by: Prospectfarms Sep 15 2011, 09:54 PM

Thanks for passing on the good info.

Posted by: avidfanjpl Sep 15 2011, 10:31 PM

So is the case toast, or can you still use it?

Thanks!

John

Posted by: Valy Sep 15 2011, 10:38 PM

You have a good point. I'm looking for a quality replacement myself and will update on that.
I forgot to add in the original post that The aftermarket "Type 1" oil pumps just don't have that cavity so there is no hydraulic piston effect. Those pumps have a flat cap that covers the pump.
Here is an example from the web. The pictured side it the outside of engine side, where the original Type 4 pump case is designed closed. This type 1 pump has a flat cap to close it. Note that the cap is completely flat so the axle doesn't go into any cavity.

Posted by: Cap'n Krusty Sep 15 2011, 10:54 PM

In the 38 years I've been intimately involved with T4 engines, from the REAL T4 cars to the busses to the 914, I've NEVER seen an oil pump failure. Never. I believe it can happen, but it's gotta be rare, and due diligence during a rebuild should catch impending issues. Actual failure in progress would result in a clatter that would be difficult to ignore by nearly anybody.

The Cap'n

Posted by: nathansnathan Sep 16 2011, 07:04 AM

I've read about this over on the shoptalkforums, I think it was Ray who was saying that they peen the housing around the pin to inhibit it coming out.

For real about there being few other options. The consensus on the best option a few years ago was the shadek Type 1 pump with a modified cover. The one I got from Jake's store around that time, the fit of the body to the case was quite loose. It being 26mm over the stock type 4 24mm didn't make any difference in pressure probably on account of the slop, even though the original pump had a chipped tooth.

Posted by: 76-914 Sep 16 2011, 08:59 AM

I posted this awhile back and although similar in appearance to yours, Jake pointed out that the failure was cam gear related and not a clearance issue. Although one should check that clearance carefully when assembling the engine.

Posted by: Valy Sep 16 2011, 11:16 AM

Cap'n,
So is your point that what I show in the pictures is just "failure in progress"?
From my perspective, this is enough failure to cause a rebuild. Anything more and it will be catastrophic.
More important, those original pumps are NLA and the aftermarket ones won't fail that way. How do you recommend to solve the problem?

Posted by: jsayre914 Sep 16 2011, 11:20 AM

Reading this thread, and building a 2056, I got on the phone with Dean @ Type 4 store. He mentioned that Jake never uses a type 4 pump on his engine but rather a modified type 1 pump. Then I found out that they do not sell this part due to the availabilty issues.

Now I want a modified pump

Where eles can I find such a beast??

Posted by: Cap'n Krusty Sep 16 2011, 11:49 AM

If that pin moves far enough to cause damage, you'd certainly be able to hear it and shut down before you caused irreparable damage. At that point, I'd have a good look and drop in another stock pump. Helps to have a bunch of 'em laying around ...............

The Cap'n

Posted by: jaxdream Sep 16 2011, 12:50 PM

Is this a Type 1 pump ??? If so what year range . I have seen that the desired pump is a Type 1 , but no mention of the year range as there is a " early " style and a " late " style . Also does this cam have straight cut gearing with the crank or helical cut gearing ?? I would suspect that a cam with a straight cut gearing would " walk " more than a helical cut gearing. The Type 4 pump can be reamadied with a little ingenuity , just drive the pin back into position , cut a grove across the face and surrouding support , fab a bar / tab that would go across the grove and be held down under the adjacenent nuts . You would have to get less thick nuts , eliminate the washer underneath , RED Loctite the nuts and all making sure that the modification doesn't get any higher than the supporting area in question already . Shouldn't be a big science project , just some real simple fab work. The idea is to keep the pin from "walking out of the boss into the path of the cam rivets / bolts , checking the distance from the rivets / bolts would give the space you need to work in +/- a few mm .
My $.02 ......

Jack

Posted by: HAM Inc Sep 16 2011, 01:18 PM

At one time Jake had a small mountain of T4 pumps with that failure. Saw it with my own eyes. Didn't look like a rare occurance to me. And it is very conceivable that the pump shaft would do it's damage very slowly over time and be difficult if not impossible to hear over the engine and road noice.

Posted by: 914_teener Sep 16 2011, 04:21 PM

Not to speak of what Jake would say....and I do respect his experience.


There are many moving parts here. Nobody has done a failure mode analysis here. So to say every stock pump is to blame or to be a potential failure of a motor would be an absolute and not necessarily accurate in every instance.

Are they prone to wear with age?...most likely. But there are many other factors that affect a failure.

The 3 O rings on the space shuttle boosters were engineered to seal off hot gases for a set period of time at a certain temperature range. In this case the failure mode was if the temperature dropped below 32 degrees. BOOM. In this case they knew that it was a problem.......just doesn't get that cold in Florida very often. Cost decision? Maybe.

I am sure the German Engineers had their own design criteria...and failure ranges. Perhaps there was a lifecyle done here....I don't know.

This doesn't even address manufacturing variables and quality.

Jake's solution is simple. They are prone to failure with age and use...don't trust them....make it new or better.

This is what this forum is about....what is better?

Posted by: HAM Inc Sep 16 2011, 06:24 PM

Clearly they aren't all failing. I don't think anyone is suggesting that. While Jake had a nice size mound of failed pumps, it is likely that statistically thay represented a minority % of the total pumps still in service. Some majority are likely still in service with out this failure.

But the truth is that professionals who see a lot of these engines see enough of the failure to look for an alternative. If an individual wants to take a chance with his own engine and re-use the pump, more power to him.

But a pro who does that knows that at some point he is likely to suffer a failure, because even if the failure rate is only 5% it still means that one out of 20 of the engines he builds is going to suffer with this issue. No thinking pro who plans to make a career in this business would take those chances. That's the sort of thing GEX does and we all know about them.

It's the same reason I replace every valve seat of every used T4 head I reman. All of the O.E. seats won't fall out, but enough do that the community knows of the problem, and as a business man I know that if I don't replace every seat once in a while a customer is going to lose one and end up very unhappy.

When a trust-worthy pro recommends replacing a 30+year old part he is not necessarily suggesting that everyone will fail if not replaced.

You can debate the statistical chances of failure and ponder the life-cycles calculated 45 years ago by the engineers. It's a fun academic exercise. But the bottom line is that when you build your engine if you reuse some of these old parts there is a reasonable chance one of them will fail.

Posted by: r_towle Sep 16 2011, 07:02 PM

Business 101, dont do things that create warrantee work
So you have heard two different business choices, Cap'n and Jake.

From a commoner like myself, with plenty of used pumps, I would replace it with used and stake the pin.

I do agree, if I heard it, I would stop the motor and investigate.

Rich

Posted by: 76-914 Sep 16 2011, 08:21 PM

Is this a Type 1 pump ??? If so what year range .


It's a Melling

Posted by: Jake Raby Sep 16 2011, 08:26 PM

I have posted the pictures before... 3 crates full of good/failed/ failing oil pumps. The first failed TIV engine I ever experienced was killed by this mode of failure. The first engine failure that I personally experienced was also caused by this. Thats the last time I used one.

Anyway, use what ever the hell you want to use.. If it works you can rejoice.. If it fails you can add to your knowledge base and use every one that you find in the future for target practice like I do... I'll upload some video of blowing these pumps up on our rifle range with incendiary ammunition. Its rather spectacular in the evening just at dusk-

Posted by: Valy Sep 20 2011, 03:05 PM

So I did some research on the possible replacements for our old oil pumps.
As I understand it, we need the type 1 pump with 8mm studs, built for flat cam.
Or original pump gear is 24mm so anything this size and bigger will be nice.

Some recommend the Melling pumps. Those pumps look solid but have a major problem: the pump body is made of cast iron. This results in a different heat expansion rate compared with the aluminum case (aluminum expands more). The result is a bigger gap between the case and pump when the engine is warm. Can be fixed by adding an elastic o-ring between the pump and case.

The other option is the Schadek pump that has a more desirable aluminum body and is much cheaper . There are also lots of good reviews for this pump.

Both pumps are available in different gear sizes, including the 26mm and High Volume 30mm gear.

Anyone is welcomed to comment on the options or just add more.

Posted by: nathansnathan Sep 20 2011, 03:59 PM

The Shadek type 1 pumps are known to have a loose fit/ slightly smaller than ideal. You can slide them into the case without loosening the parting fasteners, even. This allows oil to get between the pump and the case and will result in lower-than-ideal pressure.

Also, it should be mentioned, to use the type 1 pump you have to modify it and the cover, and run a spot-faced cam gear with clearanced bolts, and have the case split to check clearance.

Here's a great thread off thesamba baywindow forum.
http://www.thesamba.com/vw/forum/viewtopic.php?t=421504&postdays=0&postorder=asc&start=0

The Gene Berg Pump seems pretty nice, they say it's a Shadek that's been gone through and machined to take an o-ring between the pump and case. -Would have to call them to confirm that.

Posted by: Jake Raby Sep 20 2011, 05:58 PM

and the O ring that the Berg pump includes is worthless in a TIV application.. The TIV case is thinner in the oil pump area and the O ring hangs in outer space sealing nothing.