Massive Boost Leak

[huafist]

I know I've developed a MASSIVE boost leak, but at the moment I'm stumped on where it is. I was heading up the interstate today and the car lost power. I don't mean a little, I mean it won't get out of it's own way. If I added ANY throttle, the boost gauge started to build, but it wouldn't go anywhere. It went so far as 12 psi (where the MBC is set to) and it still wouldn't gain any power. It also overheated, one of the coolant lines to the oil cooler sprayed coolant all over the ground when I stopped the car.

I know it's a boost leak, but right now I don't know where to look. I'm not at home, but I happened to have my boost leak tester in the car so I hooked it up to a portable air compressor (cig. lighter type) - it builds *0* psi. No pressure whatsoever. The problem is, the compressor is so friggin' loud I can't hear the air escaping. I squirted down the throttle body, IC piping, injectors, and all vacuum lines I could get to easily with soapy water and saw nothing. I called the calvary and I'll have a bigger air compressor (one with a tank) tomorrow. Any ideas as to where the leak is?

 

[oldman]

1. Make sure none of the cylinders are in TDC which will result in valve overlap, pressure escaping through exhaust.

2. disable or turn the mbc/bcs all the way up.

3. Open the oil cap and listen for leaks.

I'm sure once you have a bigger compressor, you should be able to hear a leak that big. Good luck.

 

[huafist]

valve overlap never even entered my mind.

If I hear a leak inside the valve cover, wouldn't that mean there's a bent valve? Even though I have good compression all the way across the board?

I'm hoping I can hear it with a larger compressor - the last time I had a leak this bad you could hear it "whistle" at idle (sucking air in at vacuum), but this time you can't.

 

[oldman]

If I hear a leak inside the valve cover, wouldn't that mean there's a bent valve? Even though I have good compression all the way across the board

No, not bent valves. If you're pressurizing the crankcase, either turbo seal(normal during static pressure test as long as oil is not leaking out), defective pcv, valve seals or rings. Since you have good compression, you can probably rule out the rings. Also, if you hear air out of exhaust, check the egr as well as valve overlap.

 

[boostedgst2984]

do u still have stock IC pipes on the car. One of them could of possibly torn or cracked. If you have stock bov check around the bov seat. Yea when u get a quiet source of air let us know. I know what boost/vacum leaks are all about. I was chashing them down for months.

 

[huafist]

Ok, here's an update:

Got a bigger compressor yesterday. All I can make the system contain is ~7psi, and as soon as I unhook the compressor, it drops. Problem is, I can't find a massive leak anywhere. I have a leak at one of the vacuum nipples on the intake manifold (gotta take it out and wrap it with teflon tape I guess), a leak at the BISS, and one coming from the throttle body area that I haven't been able to track down, feels like it may be coming out around the TPS. I would assume that's shaft seals leaking?
Would that be enough to make the car a complete dog? It's so bad that if I'm doing highway speed (50 - 70), and I start up a hill, it builds boost but still loses speed. It literally has no power.

 

[oldman]

Nothing out of the oil cap or breather valve?

 

[huafist]

Nothing out of the oil cap or breather valve?

Slipped my mind to mention it, but no, nothing out of either. Checked for pressure coming out of the exhaust, too. Nothing at all. I could HEAR air escaping the throttle body area somewhere, I could even feel it when I wedged my hand down behind the TPS, but I couldn't track it down. I had had a massive leak at the bottom of the throttle body, so I had taken it all off and put new gaskets on the elbow and the body itself. Ran great after that, but now this... Perhaps the gasket blew out again? I made it from gasket material from my local auto place (nearest dealer is 60 miles away). I didn't use the thin cheap stuff either, I used the thick gasket material. At this point, I'm getting discouraged.

 

[oldman]

Slipped my mind to mention it, but no, nothing out of either. Checked for pressure coming out of the exhaust, too. Nothing at all.

That is good news.

I could HEAR air escaping the throttle body area somewhere, I could even feel it when I wedged my hand down behind the TPS

TB shaft seals like you've mentioned earlier, try turning the throttle plate and see if hissing changes.

Perhaps the gasket blew out again?

Totally possible.

I'm getting discouraged.

I have seen some of your posts in the past and I'm sure you can handle this, no need to get discouraged, just be patient and take the leaks one at a time. I suggest moving the tester to the TB elbow so you can focus on fixing the leaks at the TB and IM. Once you're able to build about 20psi there, move the tester to the IC inlet. Repeat test then finally the turbo inlet, do it in stages. 7 psi indicate some serious leakage, it can every well be the cause.

 

[huafist]

It wouldn't be so bad if I had the proper tools, but the car is like 65 or so miles from home base. I know for a fact I have a leaking coolant hose (or two), so I need to straighten that out as well. One of the culprits there seems to be one of the oil cooler lines (it was spraying coolant like Old Faithful when I stopped the car), and I think I may have a leaking heater hose as well. Until I can get the car up in the air though, I can't check them. Fortunately, I have a buddy that runs a DSM shop not too far from here, I'll probably pull the car up there tomorrow so I can get it on a lift.

As far as the boost leak problem, I'd already decided I was going to move the tester to the TB elbow. It's a whole lot less work to take off the IC piping than it is to move everything off of the turbo inlet.

Part of this should be taken as a lesson to all who read this: THE COOLANT PROBLEM IS A DIRECT RESULT OF ME BEING A CHEAP BASTARD! If I had replaced all of the coolant hoses with NEW ONES when I put the engine in, this wouldn't have happened. I'm fortunate that I don't have a warped cylinder head or blown head gasket from it (checked compression today and it's fine, ~150psi all across cold and the engine only has 125 miles on it).
The moral of the story, boys and girls, is: DON'T BE CHEAP!

I just replaced the TB gasket yet again, I'll post an update in a little while.

 

[sYnOnYx]

i hope you find your culprit. but i would just replace all the boost hoses with hard pipes.

at the moment i think i have a leak,beacuse at full boost, and when i get on it i hear a loud pshhhhhhh not the bov type either, and the bov is not as loud as it was before , re-circ is hooked up, but it was waaaay louder before. im gonna hookup a boost gauge directly to the intake manifold, andsee what psi reads there at full boost, i dont trust the stock gauge worth a damn.

 

[huafist]

i hope you find your culprit. but i would just replace all the boost hoses with hard pipes.

at the moment i think i have a leak,beacuse at full boost, and when i get on it i hear a loud pshhhhhhh not the bov type either, and the bov is not as loud as it was before , re-circ is hooked up, but it was waaaay louder before. im gonna hookup a boost gauge directly to the intake manifold, andsee what psi reads there at full boost, i dont trust the stock gauge worth a damn.

You can't really replace all of the boost hoses with hard pipes - only the intercooler piping and intake pipe. The hoses will still all be vacuum lines.
As far as your problem, you're right to not trust the factory gauge, it's shit. It only estimates what it thinks boost *SHOULD* be based on readings from the MAS and other sensors. Have you done a boost leak test yet? As has been stated earlier, you should be able to hold 20psi in the system for 45 seconds or longer on a good, sealed intake tract. Use a bottle of soapy water to help track down your leak. Good luck.

 

[huafist]

Well, the plot thickens. I made another throttle body gasket and installed it. I didn't have an air compressor handy (the one that I was using had to be returned). I decided I'd start it and move it a few parking spaces so the apartment complex owners wouldn't bi*** to my buddy about it sitting there. Well I start the car, and I hear a knocking/pinging that wasn't there before. I fired up my logger and checked it at idle, the logger doesn't read any knock until it reaches about 4k, at which point it reads ~23 counts of knock. I don't know at this point if it's a rod bearing or if it's a lifter. I'm gonna pull it to a buddy's shop and go from there. Hopefully it's just a lifter and not anything serious, as I just put the friggin' thing together 125 miles ago.