I just completed my boost leak test. The leak areas were very consistent to other threads: check valves, y-pipe, DV's, boost hose seals, vacuum elbows and throttle body gasket. Everything was leaking.

My suggestion for those who are planning to do this is to expect to address these common wear items and have them on hand before you start so you can get it done in one day.

I bought the pre-turbo test kit from Marski and built testers for pre-Ypipe and at the throttle body.

Initial Test with a 5 HP compressor:
preturbo - could not built over 5 lbs
preYpipe - had to run compressor constant to get maintain 12 lbs, lost all pressure in 3-5 seconds

Results after repairs:
@ throttlebody
quickly filled to 20lbs (5 secs) and stopped pumping air
20lbs dropped to 15 lbs in 30 sec
20lbs dropped to 10lbs in 90 sec
20lbs dropped to 5 lbs in 250 sec

Moved to testing preYpipe and got the same results

Move to testing preTurbo
took 20 seconds to build to 20 lbs
20lbs dropped to 15 lbs in 9 sec
20lbs dropped to 10lbs in 24 sec
20lbs dropped to 5 lbs in 45 sec

I could not find leaks at the connections: preturbo, post turbo or at ypipe. The wastegates stopped leaking on the second test, the 20 lbs pressure sealed them off. I could hear the air moving but don't understand where and why there is that much pressure drop preturbo.

Can anyone shed some light ? Do I need to continue looking for a leak ?

 

The two way black valve is the infamous check valve #16 they go bad and im replacing mine.

 

Nice red zip ties
Can anyone explain how to deinstall the y-pipe and throttle body? Is there a DIY around somewhere?
Thx in advance

 

I'm not sure I would have people spend lots of money on, potentially, unnecessary parts. My car is leak free and has been since day one.
Either way, congrats on tracking down your leaks! Should feel like a completely different car!

 

Any thoughts on why the pressure bleeds off so much quicker pre turbo ? There were no leaks at the hose connections or waste gates.

 

OP: Please post part numbers of suggested "parts on hand".

Thanks

 

The suggestion is from a preventative maintenance vs. repair as needed point of view. I'm in the PM camp when it's comes to items like hoses, o-rings, gaskets and known failure items. My car has 100,000 miles (70,000 mine). The hoses, gaskets and o-rings were really hard from age and heat cycles. The #16 check valve and #9 venture tube both failed. My Evo DV's were leaking externally at the nipple, I put the original bosh back in for now as new ones are on their way.

The suggested PM parts list:

 

From your pic...what are the #9 and #16 check valves...the bigger ones?

 

The little one's are the #21's if you go by the parts list quantities.

 

Right! Thanks!

 

I guess I'm not quite sure what you mean by "pre-turbo?" Did you pull the intake tubes off the compressor inlets and pressurize from there?

 

i actually changed all the items above + OEM plenum. Cost way around 500 in parts. The plenum was 180. I was brake boosting and could hear air leaking. Boost leak tested everything and 1 #21 valve was leaking 3 vac hoses and top of plenum was leaking. I do leak test every 3 months or so and it was fine last time around but with over 100k miles things do get tired. #16 was fine but might was well while I was at it.

 

Yes pulled intake tubes and connected to the turbo. It dropped pressure considerably quicker than at the Y pipe. I check all the hose connections at the turbo all the way to the y-pipe (again there was good pressure result at y-pipe) and the waste gates , no leaks.

I can hear the air moving but did not sound like the leaks I fixed. Trying to understand if there is something I'm missing.

 

I pressurize from the lower boost hoses but I guess it's essentially the same thing.
But yes, if you're dropping pressure fast, you definitely have another leak. I may loose a pound of pressure every 40 seconds or so. Maybe even longer.
I would suggest removing the rear bumper and doing the test again. You may have a leak at, or in, the intercoolers.

 

You did replace/zip tie the molded hoses at the SAI right? I had leaks there also