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]

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.



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.



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.

[914sgofast2]

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”