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on my dyno session, after my last pull i let off the gas and a puff of white smoke came from the engine(towards the firewall area). the dyno guy said i might have a leak on my rear main seal. he said that he is rebuilding a cobra right now and it has a bad rear main seal. he also said this seems to happen quite often with the cobra.

not sure if this is realted, but as of right now i know i have an exhaust leak somewhere. i can hear a very slight hissing sound. over the past few months my x-pipe has been coated with some type of black residue. it looks as if a black garbage bag melted on my x-pipe. i'm not sure where this is coming from. can an exhaust leak cause moisture to leak out making my x-pipe black?

what do you guys think abou the white puff of smoke? any ideas? is the black residue related to the rear main seal leaking? need some input, thank you.

btw, car runs fine, no check engine light or anything.
 

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White Smoke?

Sorry to hear about the smoke deal. Usually white smoke means water in the mix somewhere. But you say the car runs fine now. On my 91' the only way I identified the blown head gasket was the overflow bottle would overflow after shutting the engine down. Real weird scenario because at first it smoked for a day or two then it quit smoking and started the overflow gig. Not sure where the problem is, if any, in your case. Try checking out your exhaust leak for a quick fix there and maybe even pull the plugs to check for liquid other than gas on them. Good Luck.:confused:
 

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Re: White Smoke?

2stangBK said:
Sorry to hear about the smoke deal. Usually white smoke means water in the mix somewhere. But you say the car runs fine now. On my 91' the only way I identified the blown head gasket was the overflow bottle would overflow after shutting the engine down. Real weird scenario because at first it smoked for a day or two then it quit smoking and started the overflow gig. Not sure where the problem is, if any, in your case. Try checking out your exhaust leak for a quick fix there and maybe even pull the plugs to check for liquid other than gas on them. Good Luck.:confused:
i recently changed out my plugs about 2,000 miles ago. they all seemed normal. the car has only 22,500 miles on it. its weird b/c i did a total of 3 pulls. the first 2 pulls when i shutdown, it was normal. on the 3rd pull when i shutdown thats when the puff of smoke came up. any more ideas?
 

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An oil analysis (kits are ~$20 in auto parts stores) will tell you if you have coolant in your oil (along with a ton of other stuff).

It could have been caused by something falling onto a part of exhaust (from your description of it's location). Could have been something clinging to the body got knocked loose by vibration and {poof} up in smoke. I would be concerned if it is repeatable. Unfortunately a dyno is the best way to repeat that scenerio.

An exhaust leak could have similar symptoms. That black gunk you described could be from an oil leak, but it would have to be minor or you'd see oil under the car. If the rear seal was bad, you'd see oil under the car, would probably look like the leak was coming from inside the bell housing. Another possibility is that thye front tranny seal is leaking. My stock tranny had such a leak when it was pulled.

Good luck tracking it down.
 
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