cant find or hear this boost leak

[dacowgod]

Hey guys I am working on my brothers car and cannot find his boost leak. I am not new to how to use a boost leak tester, and know the soapy water tricks etc... Main problem here is i cannot even hear the leak..

heres a little bit of info..

the PCV valve is good.. but i still have boost leaking into the crankcase. to null this problem i have capped the dipstick hole and the pcv valve and breather hole on the valve cover... this allows me to accept the fact that the crankcase is seeing some boost.. but allows me to rule it out as the Major leak. since if i pull the cap off the dipstick the crank case will actually pressurize during the boost leak test .


I figure the crankcase leak is caused by the valve seals because we just reringed the engine about 200 miles ago and i have good compression across the board.

The car runs good.. I am just nit picky and want optimal performance.. so obviously boost leak is high on the list...

I'm Not really sure what the vacuum is at idle though we dont have a gauge that reads it.

My bet is since i cannot hear any boost leaks.... that it is going straight out the exhaust, although i cant hear anything or feel anything out of the tailpipe. this is the only place i can imagine it going....

. I have set the crank to 30 degrees ATDC to solve any overlap but that is no luck.

also I am checking directly from the throttle body elbow... to rule out the rest of the intercooler/piping for now.

My next step is going to be check the egr valve... i guess it could be stuck open.. letting the air into the exhaust...

Oh and just to clarify I have warmed the engine up before i did the test, to avoid the possibility of air escaping around the rings.


anyways sorry for such a long post, i just wanted to be as informative as possible to filter out some suggestions that I have already tried.


Any other ideas where the air is going??...

Thanks in advance.

 

[dsmchick44]

I would do the soap test...your not going to be able to hear a small boost leak. You dont need to hear it, just need to find where the soap is bubbling which indicates the leak.

 

[cruisintalonawd]

I would do the soap test...your not going to be able to hear a small boost leak. You dont need to hear it, just need to find where the soap is bubbling which indicates the leak.

X2 for soap I found a bunch of small leaks with soapy water

 

[mitch26753]

I would do the soap test...your not going to be able to hear a small boost leak. You dont need to hear it, just need to find where the soap is bubbling which indicates the leak.

Damn she knows dsm's and she's HOT. Dream come true! Oh yeah back to the boost leak. Try the soap test, if that doesn't work just start going down every line and checking them out. They are bad for cracking around where the hose connects to the nipple.

 

[BoostFrenzy]

If the car has a MBC, cap those hoses off because MBC are notorious for leaking during a BLT.

 

[cruisintalonawd]

If the car has a MBC, cap those hoses off because MBC are notorious for leaking during a BLT.

i didn't do that and it didnt leak.....musta been a lucky

 

[dacowgod]

the first line states I know about the soapy water trick.... which implyed I have tried it.. no success .. I am looking for a place for a a huge leak...something the soap test would be limited for detecting as my ears would be limited for hearing... I thought about the brake booster leaking last night, I didnt cap off the brake booster, just left it hooked up so if it were to be bad i suppose a bunch of air could escape there.. Would expect I'd notice an issue when braking but I will pull off the line and cap it for sake of the boost leak test.... so basically other than EGR can anybody put in another idea of where all this elusive air is going.. Thanks for the posts.

 

[dacowgod]

sorry forgot to address the comment made by boostfrenzy... since i am boost leak testing from the tb elbow, It factors out the MBC in my situation .. as it is connected to the nipple from the turbo. It doesnt see any air from the boost test... thanks for the suggestion though..

 

[rich3389]

from the tb....tb seal, tb gaskets, emission and fuel pressure reg. vac lines, BOV and BOV booster line, injector seals, manifold gasket...I am surprised that you cant hear this leak when you do the BLT.

 

[dacowgod]

ya also surprised... there are leaks around the tb shaft seals but not all my air worth .. .. all the rest are blocked off or tested... Im going to try to replace the egr valve this week and see if that helps the issue...thanks for the posts... I will post back when i find the cause..

 

[divinaand_1]

If you still have leaks you cant find, get likes a can thats filled up with colored smoke and you'll see where the leak is.(kinda like a spray can paint ) spray it inside the system and it shall leak out and show where the leak is.

 

[9 T GSX]

How are you boost testing from the t/b elbow? BLT are normally done with it connected at the turbo? this is untrue "i am boost leak testing from the tb elbow, It factors out the MBC". If is connected to the intake system it will pressurise and leak.If it doesnt then how would the mbc control boost? What is the car actually doing?you say its running good and you cant hear any leaks, so reading this i'm thinking if you cant hear any leaks there arent any. Do you have a aftermarket FPR?

 

[c4uldr0n]

Have you done a compression test? Maybe you have leaky valve seals or valve related problems.

 

[kenamond]

Some of you should probably read what the OP has already said, because he's already covered most of the bases being suggested. He has good compression, if the MBC is from compressor-to-WGA, that's upwind of the TB, if you test at the TB elbow, you know your leak is somewhere between the TB elbow and the combustion chamber, yes you can BLT at the TB elbow, soapy water doesn't work on very large leaks (though you can usually hear the hiss) nor leaks in other components connected to the intake via vaccuum lines.

OP: Does it help when you cap the VC breather, PCV, and dipstick? Have you tried any hearing aids like a hose so that you can reach under the IM-to-head gasket and listen "closely" to hisses near things you can't get your ear next to? Have you tried capping vaccuum fittings?

What is the result of the BLT? Can you not pressurize at all? How high can you get and how does it leak down? For example, does it go to 20psi and leak down to 10psi quickly then slow down until 5psi then hold, or does it just dive quickly back to 0psi?

If you could eliminate the known leaks, that might elimintate the unlikely case that the leak was bigger than you thought. I realize that it's a pain to replace TB gaskets and then find a leak that requires you to tear the TB back off, but it might be worth it...I just don't know how bad it's leaking to have the same sense as you that the leak is too large to be caused by some of the known leaks.

I'm sort of thinking out loud and don't have any ideas that you haven't aluded to yet, but maybe it'll trigger that lightbulb in your head...or maybe not.