TheSamba.com :: View topic - Engine runs for first time! (now, low oil pressure)

Sun Mar 21, 2010 1:51 pm

Desertbusman wrote: Sorry you don't have this resolved yet. Even though I keep away from T-4's there are a couple things that seem to stand out.

WhirledTraveller wrote: Just an update, I dropped the oil control piston (easier than I thought) and took a look at it. It moved easily in the bore but the surface was quite rough so I smoothed it out with sandpaper on a flat surface, ending with 2000 grit.
Before:

After:

If T-4 control valves function like T-1's the concern is the OD of the piston and the fit in the bore. The end has nothing to do with anything. Sanding the end on a flat surface wouldn't do anything good or bad just waste time. Sounds like you indicate it might have been loose in the case bore. I have to shove a wood dowel in mine to pull them out. Might be worth a new replacement of the piston and spring. It needs to be loose enough that it it can move without hanging up but any more looseness is bad. Evidently some people need to sleeve the bore. Another thing if the diameter is the same as a T-1 you might have the wrong one. There are different configuration pistons with different grooves and different top chamfers and they act differently.
Another thing is hearing about pumps that have an O ring just around the the suction and around the pressure port to prevent any leakage. Pump body to case clearance isn't a concern with those. There are two different types and thickness gaskets for the pump body and the cover. Could you have them switched? Also I run a 26mm pump on one engine and a 30mm on another. Sure it wastes a bit of HP but I'd rather have maximum lubrication. And it seems to run cooler. And have never gotten close to a light flicker according to the gauge. A used 24mm sounds real puney. Anyway just thoughts to ponder over and again that's from my T-1's. May or may not apply to yours. Hope you get something good resolved.

This is not quite correct. This is also precisely why they make a tool for refacing the bore where the end of the piston seats. Its common that it is too rough for a proper seal. From quotes from those who have used this refacing bit...it can make about 5-10 psi difference in low rpm oil pressure that is not leaking past the face of the piston.

One of the potential issues of having oil too thick in VW's is that the excessive pressure on engines that are fit and tight can offset the calibration of the spring for the oil pressure relief valve....causing it to bypass when it should not.....sending oil back to the case when it should be going through the cooler. Ray

Sun Mar 21, 2010 6:50 pm

what kind of pressure are you seeing 4K RPM with the oil at 180+?

Sun Mar 21, 2010 7:43 pm

Jake Raby wrote: what kind of pressure are you seeing 4K RPM with the oil at 180+?

With the 26mm Shadek I was seeing low 40's with 20W50 and high 30's with the 10W40. Now that I've switched to the T4 pump I haven't taken a good highway run yet so I'll have to try it and see.

Mon Mar 22, 2010 6:18 am

I bought the type IV pump brand new from CB performance,
and I get 60-80psi at startup, and around 10-20 psi driving around at idle.

My light never comes on. Did you use the guy in hopkinton as your builder?

Mon Mar 22, 2010 6:44 am

Kosmo wrote: I bought the type IV pump brand new from CB performance,
and I get 60-80psi at startup, and around 10-20 psi driving around at idle.

My light never comes on. Did you use the guy in hopkinton as your builder?

Can you send me a link to that pump? I am interested.

Mon Mar 22, 2010 10:55 am

Kosmo wrote: I bought the type IV pump brand new from CB performance,
and I get 60-80psi at startup, and around 10-20 psi driving around at idle.

My light never comes on. Did you use the guy in hopkinton as your builder?

yeah I did. I took the bus for a long drive today and the type 4 pump is definately not doing as good as the Shadek was... I'm only getting 30psi at 4k rpm and this is with 20W50... ouch. All I've done is made things worse. From what I can tell every aftermarket pump made is around 2.755 and will be to small for my case unless I get one custom made or O-ring it.