Evo ix with 155k miles. Stock engine, turbo, head. Has been running 24 psi for 100k+ miles. Now it only wants to boost 16psi. I fixed minor boost leaks, but still a major one exists through the engine: out of the valve cover, and dip stick. (it's not pcv valve). It leaks from 15psi to 0 in under 10 sec. (It holds boost up to the manifold)
I did a compression test and I am getting 130, 96, 105, 135 from cyl 1 to 4.
Engine doesn't burn any oil, the turbo has minimal shaft play only in and out.
When you combine the compression, and leak...What are your suggestions? Head work, valves?

 

i ran 90psi in cyl 3 for two years. no amount of tuning or track days phased it LOL.

you definitely need to find your boost leak. until then, your poor turbo is working extra hard. if it's having a problem building more than 16psi, it could be a really big leak.

as for why your compression is low, you will need to do a leakdown test.

you aren't doing a boost leak test with the throttle body open, are you?

 

I am thinking of doing the leakdown test next.
The throttle should be open, air does pass easily to the intake manifold during boost leak test.
If I block the last IC pipe before the manifold I can hold boost, as long as I don't push it too much, because my stock evo ix bov will open due to no back pressure.
All the air is leaking through the valve cover

 

who told you the TB should be open? if you are doing it that way, then of course you are going to get air coming out all over the place.

i test my setup to 25-30psi. the reference line on the DV will help keep it closed.

 

How do you keep the TB closed, mine passes air easily? The reference line is connected to the manifold which is after the TB. So if I don't have positive pressure there, than the BOV will open.

 

if you don't touch the TB, it stays closed. now that you mention it, i'm forgetting how i kept the DV closed LOL. i'd have to look. it's been a while.

you should only be pressuring from the turbo inlet to the throttle body. if you have air coming from the dipstick and valve cover, you may be doing it incorrectly.

 

I have been reading that people pressurize the whole system. Otherwise how would you check if a hose is leaking somewhere on the intake manifold. If I pressurize from turbo to TB I am ok. Something is happening in the manifold/head, because it's leaking a lot from the VC breather

 

yes, if you force air past the throttle body, it is going to go into the IM, through the head, out of the valve cover, past the valves that are open, into the cylinders, into the crank case, out of the dipstick tube.
that is not how you to a pressure test.

if you have a vacuum leak from one of the lines on the IM, then you check for a vacuum leak the way you normally would. personally, i run the car and spray carb cleaner until the idle returns to normal. i also zip tie all of my lines juuuuust in case.

 

Here is a link of a boost leak test:
https://cobbtuning.zendesk.com/hc/en...e-System-Leaks

They fill up the IM, and check the injectors for leaks.
I do not touch the TB, it stays open by it self. I don't press the gas pedal or anything.

 

i'm at work and only scanned the article, but i didn't see anywhere it said to leave the TB open.

 

I am not opening the TB. I keep it close, but air passes through.
In the article, how are they checking the injectors for leaks if air does not enter the manifold?

 

i actually don't know. i've always used carb cleaner during idle to check. i suppose you could build enough pressure with a boost test. hm....

you learn something new every day

 

Anyone has more suggestion on my massive boost leak through the Valve Cover.
I read over 20 forums on this problem. A lot of people have this leak, but not one solution.

 

that's not a boost leak. it's air getting past open valves.

 

Even if the valves are open, the air should not get to the VC. it should go in the cylinder and then out the exhaust valve, and the exhaust, but not the VC. Unless the valve seals are leaking than air should not get to the VC, and I don't think the valve seals are leaking since it doesn't burn oil or smoke.