Type 4 oil pump rebuild, Comparison of OEM vs. Samba CNC pump Options

[Superhawk996]

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.



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.



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.





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.

[Superhawk996]

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.



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.




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? (IMG:style_emoticons/default/confused24.gif) 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.



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.



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.