oil pump, which one Options

[Superhawk996]

Read the Samba thread.....
Holy Crap. Not sure I can do that. Of all tools he mentions I have a magnetic dial, the punch and hammer and that's about it.

That thread is extensive but good on you for self assessing that you can’t do it all. That post really lays out the ideal approach of measuring gear lash, lapping in end clearance to perfection, etc.

Here’s the practical approach. See photos

Clean up that pump. Inspect gears for pitting. Subjectively feel the backlash, should barely be perceptible. Inspect housing for any scoring.

Unless the engine grenades and pumped shrapnel or was seriously abused, most oil pumps are suitable for reuse. Oil pumps by their nature are oil immersed and over lubricated so actual unusable wear is pretty rare.

Gear pitting - bad (scrap)


Pump body - near perfect


Pump body badly scored and damaged - scrap

[Superhawk996]

Post photos of your parts after clean up including the other side of the end plate to see if the idler shaft has migrated at all (they usually don’t unless the engine was overheated).

[trojanhorsepower]

Had a minute to clean the pump. Hear are some more pics.

[Superhawk996]

That pump is looking pretty promising.

In the pump body - is there a noticeable “step” where one gear has worn lower than the other or is this little area just a lighting & photo abominably.

Disregard the milled oval slot and that little triangular point from machining. I’m asking about the area where the two circular gear wear patterns overlap.


Post photo of the other side of the end plate like this view so we can see where the idler shaft is at and whether it has been pushed out toward the cam. This perspective

[Superhawk996]

Also is there any noticeable feel or roughness difference in this area or is this just lighting and residual dirty oil?

[trojanhorsepower]

OK I don't feel anything where the two circles meet.
The other spot there is one scratch I can feel.

[trojanhorsepower]

The shaft looks much further in on this pump then the one you posted.

[Superhawk996]

Ok so let’s summarize:

That is a pretty decent pump from what I can see in photos. Would be ideal to do the whole Samba “blueprinting” procedure to make it perfect but recognize that isn’t possible right now with the tools, time or patience you have. No shame there.

What would I do?

I wouldn’t hesitate to use that T4 pump to swap for the existing T1 pump. At a minimum it will solve the problem of the T1 pump internal leakage problem that is widely acknowledged with undersized T1 pump bodies.

If it solves your oil pressure problem you will have also verified the effectiveness of the previously used pump. If it makes good pressure hot and cold - you’re good to go. Keep it in there and (IMG:style_emoticons/default/driving.gif) Think of it as troubleshooting. If it doesn’t solve your pressure problem you are no worse off and will eventually have to split that case to get to the root cause.

With respect to the idler shaft being so much deeper. I have seen this before.



I’m not going to pretend I know the whole history of these T4 pumps and how VW may have changed or updated them over year and models including T4 bus and 411/412, etc. if anyone knows more detail on how the T4 pumps evolved - please post. I’m leaning new stuff even after all these years.

When I saw this on one of my T4 parts I assumed it was someone swapping in T1 parts (idler shaft and gears) but perhaps there was a lot of variation in these parts as VW recognised the potential migration issues? (IMG:style_emoticons/default/confused24.gif)

Having the shaft deeper may be an engineering fix for the bad failure mode where the shaft can migrate into contact with the cam rivets if the engine is overheated.

Overheating expands the aluminum oil pump end plate hole faster than the steel idler shaft. This loosens the press fit and potentially allows the shaft to begin to migrate as oil pressure gets behind it.

By shortening the idler shaft it effectively makes it much less likely the shaft could migrate far enough to begin to touch the cam.

Per the Samba procedure - pinning or peening the shaft addresses this. The T1 idler shaft isn’t fundamentally different. The T1 pumps I’ve seen have a factory peened shaft

I would peen the T4 pump end plate idler shaft bore (just to be safe). I prefer pinning but recognize you don’t have to tools to do that.

How to peen the shaft:
Use a hammer and chisel / cold punch and just deform the end of the shaft hole such that if the shaft were to ever migrate, it would encounter an undersize hole that will then limit the shaft from moving further.

[Superhawk996]

Here is an example of the T1 Shadek pump factory peen.



Keep in mind, I’ve seen some of the T1 pumps that are modified for T4 use and this factory peen get machined off. Effectively leaving you with an unpeened idler . . . Just like the OEM T4 pump that everyone dogs for the potential migration issue. Go figure (IMG:style_emoticons/default/headbang.gif) see amount machined off (arrow) and lack of peen of what’s left (circled). I’m not suggesting all are this way, just the one I had in my hand based on what I personally saw.



So I’ve seen different peened T4 parts and sometimes it’s a combination of multiple small peened spots and other times it’s just two or three bigger peens like the Shadek. I don’t think it matters all that much as long as the ID of that idler shaft bore is deformed enough to prevent the shaft from ever coming out proud of the pump body.

Example of peened with multiple little deformations around circumference of the idler shaft hole.

[trojanhorsepower]

OK, thanks for all the advice. I will swap the T1 for this T4 later this year and report back.

Just out of curiosity is there anyone that sells refurbished (like the Samba) oil pumps?

[Superhawk996]

Just out of curiosity is there anyone that sells refurbished (like the Samba) oil pumps?

Not that I’m aware of.

The problem is the labor to do the work makes the refurbished T4 pump cost uncompetitive to just buying a T1 pump. I was away from hardcore 914 work from about 1999-2018. Somewhere in there, it appears everyone started using T1 pumps because they are cheap and T4 pumps became NLA.

Maybe at one point the T1 pumps fit better? But based on the Raby post of him doing his own billet CNC pumps I’m inferring that they were always somewhat of a problem for him to get properly sized T1 pumps too.

When I bought that billet CNC 30mm T4 pump that was around $300. Gives you an idea of why so many are highly motivated to use the modified T1 pumps regardless of the warts. Using a $300 pump on a $25k engine build makes sense.

But to reiterate, oil pumps rarely fail unless abused by
1) Overheating
2) Running out of oil and running them dry
3) Engine damage occurs & shrapnel gets ingested and score the pump body, end plate, and gears.
4) Pump / engine sat outside exposed to weather, acidic oil, water/rust damage, etc.

Many could simply reuse their old T4 pump but they have been misled into thinking the new $50 or $60 modified Shadek is always better than a used T4 pump which isn’t always the case. Again: may have made sense at some point but given current T1 pump size issues I personally don’t think this still applies.

A great example of this ability to reuse oil pumps shows up in the 911 world where it’s a whole lot more common to reuse oil pumps and oil coolers unless something catastrophic has occurred. The difference there being a new 4 rib oil pump will set you back $1000 ish. Not an apples to apples comparison as the 911 pump is way more complicated than the T4 pump but you get the point of why reuse is so much more common.