BOOSTD

A few nights ago I used the homemade pressure tester to check for boost leaks. I pulled the intake elbow off the airbox and capped it, removed the PCV and capped the hole in the intake elbow, and pulled the hose off the intake manifold to pressurize it from that end. I added only a pound or two of pressure and could hear oil gurgling. I removed the oil filler cap and put my ear over it to confirm. It seems that the pressure was pushing oil up the turbo oil feed line backwards into the block, as if air was getting past the front seal on the turbo and up the oil feed line. Once I heard the oil moving I aborted the test and didn't try adding anymore pressure. Has anyone else heard this when pressure testing, or is it a sign of the lost boost pressure I'm having?

Someone else also heard the same thing when pressure testing an '02 A4 and it has all stock plumbing (except for chip).

YellowA4Turbo Ownz

I did a pressure test on a car once and I heard air leaking from the dipstick hole.

pikejerky

gurgle sound. Search this forum for "kirk deviation" late spring early summer 2003.

BOOSTD

I say that because I assumed that removing the PCV would have prevented the oil being pressurized. I'd like to know how that's happening.

Also, if the oil is being pushed back into the block, how would pressure be maintained (either with a pressure tester or while the car is under boost trying to maintain 20psi?)

Yippers®

pressure in the cartridge doesn't somehow seal what absent oil pressure leaks air back into the supply line? Strikes me if the turbo seal was bad you'd pump a fair amount of oil into the intake.

pikejerky

I had no problems except a slightly high long term fuel trim. Kirk had a negative deviation IIRC but only above 5500rpm. My pump wasn't fast enough to presurise the system adequately before it bubbled out at the block but Kirk's test seemed to rule out any leaks since he was able to pressurize quicker than it would escape in the block. Both cars were '00 ATW.

pikejerky

makes sense. oil pressure at 3000rpm is 70-100psi according to Bentley

DAP@EPL

I've pressure tested 3 different S4s and they've all done that. Tested up to ~10 psi and never noticed any ill effects from the oil gurgling. I have found a few boost leaks though!

-Dave Pramanik

BOOSTD

same, ATW engine code. back to testing.

xr4tic

I think the oil pressure seals up the turbo and prevents leaks, since the oil pressure is more than the boost.