1999 GST Underhood Exhaust leak
1999 GST Underhood Exhaust leak
08-27-2010, 08:37 AM
I am trying to get an idea of most likely cause and worst case scenario. I can smell it and hear it, not so much at idle but when revved, strong smell. THe car appears to be bone stock.
Any thoughts or advice is appreciated. Thanks in advance.
08-27-2010, 12:05 PM
Well if you have an exhaust leak it can cause the car to run rich. Exhaust leaks make you o2s think you are lean. First you need to figure out where the leak is coming from. Make sure it is in fact a simple gasket leaking and not something cracked. More than likely it is a gasket and can be fixed with minimal work. You may also want to check the shaft play in the turbo before buying the car to make sure the turbo will not need a rebuild.
08-27-2010, 12:18 PM
Thanks for the info. Right on top I see the head to manifold gasket then the manifold to turbo-in (?) square gasket and I assume there is another turbo-out to rest of exhaust system gasket. The first two seem pretty easy to replace, the next I am not sure.
How would I check the turbo shaft play and how much is OK ? I am guessing radial play is worse than axial (back and forth) play, at least that's how it is on wheel bearings. Sounds like it could be a take apart activity.
Thanks again for your help.
08-27-2010, 10:10 PM
Best bet is to turn the car on after its been sitting for a while and the motor is relatively cold. Turn it on and instantly start feeling for air that is coming out from the gasket. This has to be done quick, because unless it's a huge leak, the heat from everything will start rising and it'll feel like a leak as well.
You are right about the 3 gaskets, all of which are not hard to replace. Hardest would be the head->manifold gasket. Just soak the hell out of the bolts (all of them) with WD40 or any other lubriacant.
These manifolds are known for cracking as well. A small hairline fracture will cause a decent leak, and will only get worse. Good thing, these manifolds are easy to come by in great shape, or you could always upgrade.
As far as checking fo shaft play, you can either pull the exhaust side off or the intake side. Intake is easy. Should be a single C-Clamp, that you just unhook, and you'll see the compressor blades. Wiggle it back & forth, and in & out. Anyway that you move it, it should NOT move with you. Very slight play is acceptable. Extensive shaft-play will cause the turbo to burn oil and oinly get worse in time. Assumming that it's still the stock turbo and has never been replace, I'm guessing it will have play. Rebuilds are doable, turbos can be replaced, or they can be upgraded. All depends on what you want to do to it.
Let us know if you need anything else.
08-28-2010, 09:00 AM
To make it more clear there should be no in and out play and slight up and down. Maybe 1mm. If the car has not been ran in a while it may have a little more play since no oil will be on the bearings. When oil gets in it they will tighten up a little bit.
09-03-2010, 01:02 PM
Thanks for the info SilvrEclipse and david-b. It was real helpful. We ended up not buying that car and are looking at another in much better shape. Looked at it today, no exhaust leak, engine sounds and runs good (has an occasional miss at idle) and is in good shape. Will take a second look tomorrow.
09-04-2010, 05:09 PM
Cool man post up some pics if you end up buying it
09-16-2010, 05:02 PM
Ended up buying a 98 GST. IT has a few challenges as well but no exhaust leak.
Thanks for all the comments. I learn slow but I do learn.
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