stock oil pump question

[HerrMahnenschmidt]

I have searched for and read nigh every thread on the topic of T4 oil pumps, stock and aftermarket. No mention of this problem that I have found.

In this photo, the drive tang on both pumps has noticeable wear (red-circled). The clean pump is from a GE engine being rebuilt; the dirty pump from a spare GD engine. The wear spot is present on the same side on both ends of the tang. Both engines had stock cams/gears in them. I do not see any corresponding wear on the cam drive slot on either cam.

Is this wear normal and acceptable? Is there a known cause and fix? Should I be concerned, or perhaps up my dosage of Lexapro?

42?

Has the CB Performance 1829 Maxi Pump 1 for 914/T4 application proven to be a reliable replacement?

http://www.cbperformance.com/ProductDetails.asp?ProductCode=1829

_________________
1977 Westfalia --
- rebuilt stock-spec 2.0l FI engine; 002 tranny w/stock gearing with 215mm flywheel/clutch/pp

[SGKent]

they all wear there. The more the wear, the longer it has been in use. Usually the more wear there is there, the more freeplay there is in the gears. There is a spec in Bentley for acceptable wear limits. Phil - Whip 618 can tighten up some of the play but not all of it.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[HerrMahnenschmidt]

Thanks. Of course while continuing to search after posting this I was able to find a pic posted by TCash showing the same symptom --

Fair enough...
_________________
1977 Westfalia --
- rebuilt stock-spec 2.0l FI engine; 002 tranny w/stock gearing with 215mm flywheel/clutch/pp

[raygreenwood]

Yep...thats the pump whose engine died due to contact with the cam gear bolts.
Classic mark on the aluminum boss and on the nuts. I have one worse than that as a trophy. I learned the hard way. Double thrust cam bearings with careful checking of the gap between highest point on cam and the highest point on the oil pump case.

The drive tang wear you see.....is common....but its better or worse depending on exactly how far out of actual center the oil pump is versus the center of thee cam casting boss.

See...there is some manufacturing tolerance in the centerline location of the oil pump....and some casting variation in location of the cam centerline in the case and some tolerance in the oil pump bore location.

There is not much difference in any one of these items...but when you add them all up....the center line of the oil pump shaft is not exactly perfect with the center line of the cam. Most of the difference is in the oil pump bore location....if it were not we would have serious issues with timing gear lash....and not just a +/- 1,2,3 etc.

The wear spot is where the lead corner touches the wall of the slot. If the oil pump centerline were perfect with the cam...you would see nothing but a fine silver line of wear on the corner of the tang maybe .003-.005" wide.

I have seen a very few early 411 and 412 cases this well entered. But as the off center and unaligned shafts turn the tang flank rubs all the way along the wall of the slot in the cam like an eccentric love-joy coupling on a pump shaft.
You will see corresponding wear in the slot wall.


Ray

[HerrMahnenschmidt]

That is an interesting solution on the part of those detail-obsessed Germans.; essentially a type of U-joint...

I will put the original 'clean' pump back in service then. The lash and clearances on it are tight, so it should continue to pump for at least the life of this rebuild.

Thanks SGKent & Ray.
_________________
1977 Westfalia --
- rebuilt stock-spec 2.0l FI engine; 002 tranny w/stock gearing with 215mm flywheel/clutch/pp

[Wildthings]

Disassemble the pump and change out the o-ring. You can also press out the idler shaft and then grind it about 1/16 shorter. (Note that some shafts are already plenty short enough.) This will allow you to do a better staking job so the shaft is less apt to walk out and hit the cam.

[airschooled]

We can we do to eliminate this wear, or is it not worth worrying about?

Do T1 pump/cam gear setups have this issue too?
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[SGKent]

[Tcash]

Do T1 pump/cam gear setups have this issue too?
That's affirmative.

[Wildthings]

[raygreenwood]

Also....making sure you have proper/best oil pump to cam slot depth settings and proper end play control of your cam is key.....for even more important reasons than just tang wear.

A great and very cheap modification is to run a double thrust bearing set. It is insurance against failure and has better control over in/out oscillation of what tolerance there is....so less wear on the tang as well.

The double thrust bearing set used to be available from the type 4 store. In a pinch just buy two sets of single thrust bearings and make your own. Ray

[HerrMahnenschmidt]

After several hours spent grokking my oil pump, I have to wonder why no one (VW?) has thought to machine an internal circlip groove to retain the idler shaft. I know that requires machining (=$$$), but a circlip would be a much more reassuring way to retain the shaft, rather than peening or pinning. Properly implemented, I think a circlip would be much less likely to get loose and bounce around than a pin.

Geez I wish I had access to a basic machine shop...
_________________
1977 Westfalia --
- rebuilt stock-spec 2.0l FI engine; 002 tranny w/stock gearing with 215mm flywheel/clutch/pp

[raygreenwood]

Pinning the shaft is actually perfect. To do this you need a good basic drill vise and a decent drill press. Dont try to do this with a hand drill

You need to set the pump up in the drill vise so that the shaft is clamped so it cannot squirm or move. Then put a small flat spot with a file in the correct location. Then centerpunch it....then turn the drill by hand until you start to get decent centered penetration.
Use a sharp high speed steel bit and a very good tapping oil for a lube.... Castrol moly dee or take some tapping fluid and mix with a dab of cv grease.....just like you would do when drilling chromoly or other hard steels.

All you need is about a 3/64" split tension pin. Then trim each end leaving them with about 1/16" stickjng out on each side and then distort each end so it cant work out. Ray

[SGKent]

they can be pinned with a set screw and red loctite.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[Wildthings]

Actually if you just press the idler shaft out, clean everything with brake cleaner, and then reinstall the pin with some cylindrical parts Loctite it isn't going to be ever apt to move.

http://www.loctite.com.au/3320_AUE_HTML.htm?iname=...0000009RF0

[raygreenwood]