Boost Leak Test

five7driver · **Posted:** Thu Feb 01, 2018 10:33 am

Hi All,
I'm trying to track down a possible turbo boost leak and I can't find a definitive guide for how to properly do a leak test. Is there a "how to" or a link for this?

Specifically, I've heard reference made to having the crank positioned to ensure the intake valves are all closed so that the test pressure isn't just leaking through the valves. At the risk of sounding ignorant, what position of the crank ensures the intake valves are closed?

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

All intake valves cannot be closed at the same time.

flash7210 · **Posted:** Thu Feb 01, 2018 1:23 pm

I don't think there is any crank position where all the intake valves are completely closed.

What makes you think you have a boost leak?
Are you getting a P0299 underboost code?
Is your boost gauge or MAP sensor showing lower than normal boost pressure?
Are you hearing the sound of air rushing out at high acceleration?

First thing I would do is clean or replace the MAP sensor and make sure all you clamps are tight.
Second, remove both CAC hoses and carefully inspect them for tears and cracks.
Third, replace both vacuum control solenoids behind the air filter box.
Fourth, cap off the inlet and outlet of the intercooler and use a compressor to pressurize it to 25psi. Then check for leaks at the intercooler.

five7driver · **Posted:** Thu Feb 01, 2018 2:45 pm

Thanks for the replies. Yes, that's what I thought: at least one intake valve will be open in any crank position. I read (somewhere) about a boost pressure test that only connected at the CAC hose from the turbo with the idea that it would check everything, including the intake manifold itself, but the author mentioned that all the intake valves needed to be closed for it to work(??)

Anyway, I managed to block things off to my satisfaction and pressurized things to where I'm fairly certain there is no leak between the turbo and the intake manifold.

Flash, I've been battling the "low/no boost, heavy black smoke" problem for about two weeks and have gone through many, many hours of checks and tests. I plan to put up a new post later today with a more complete rundown of everything I've done, because I think I'm getting nowhere...

WWDiesel · **Posted:** Thu Feb 01, 2018 4:10 pm

Flashes advice is good: Bad MAP sensor could cause this problem and DAT codes should help you identify issue. :wink:

Does it still have the EGR valve in operation?
If so, it very well could be the EGR valve sticking at times and allowing boost loss backwards through the valve into the exhaust manifold that you would never be able to see or hear.
If you still have the EGR valve, you can install a very simple EGR "Block Off Plate" that you can make out of a metal lid off a soup or vegetable can. See diagram below
See this thread for install details:> viewtopic.php?p=804565#p804565

If you have already removed the EGR valve and have thoroughly tested everything else for boost leakage and have found no apparent leaks.
I would look closely at the turbo boost controls on top of the right fender, vacuum lines, and turbo vane operator and linkage on the turbo for full movement and ensure it is not sticking by manually stroking it while the engine is OFF!
The turbo actuator solenoid can be temporarily bypassed for a test when low boost conditions are present!
See this thread:> viewtopic.php?p=918693#p918693

five7driver · **Posted:** Thu Feb 01, 2018 11:27 pm

Please see my post "No Boost" for a continuation of this story....

Boost Leak Test

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