exhaust leak

hottigr

hottigr

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Trying to chase down an exhaust leak. Had it for a few years, but lately it's permeating the cabin more than it was. Don't smell any exhaust while under throttle with the windows down (with hardtop), but, the minute I take my foot off the gas there is exhaust smell in the cabin. If I have the windows up (with hardtop), there is no exhaust smell in the cabin under throttle or on deceleration. I can find no external signs of a leak, no unusual noises under the hood. I have 289 heads with what looks like thick paper gaskets, and I can't remember changing them for at least the last couple of decades. I suspect the header gaskets, but have no proof and would really like to be able to verify the leak before I tear everything apart. Any ideas? Thanks. Kirk
 
Warren

Warren

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Sea foam

The other day I tried some of that seafoam in one of my driver cars to supposedly decarbonize the intake manifold by spraying it down the intake while running. It made James Bond's
smoke screen look like a little bbq.
Using some on a breezy day may make, your leak visible. I had a downpipe on one side that would always loosen up from the exhaust manifold. Every thousand miles or so it would take a little tightening.

PS I would also check all of those rubber grommets that seal the engine compartment from your passenger compartment as well as the fuel pump door. Not much experience with hardtops but possibly something to block off your boot well would be great for noise separation as well since you never take off your hardtop anyway :)
 
hottigr

hottigr

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825
Warren said:
The other day I tried some of that seafoam in one of my driver cars to supposedly decarbonize the intake manifold by spraying it down the intake while running. It made James Bond's
smoke screen look like a little bbq.
Using some on a breezy day may make, your leak visible. I had a downpipe on one side that would always loosen up from the exhaust manifold. Every thousand miles or so it would take a little tightening.

PS I would also check all of those rubber grommets that seal the engine compartment from your passenger compartment as well as the fuel pump door. Not much experience with hardtops but possibly something to block off your boot well would be great for noise separation as well since you never take off your hardtop anyway :)
Click to expand...

Some good tips, Warren. I've done the grommet check before, but who knows if one might have fallen out. The Get Smart smoke screen might work. Never say never- I once took the hard top off for some pictures;)
 
hottigr

hottigr

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825
I put 1" painters tape around the entire trunk gap and that took care of at least 90% of the issue. There must be a large negative pressure area around the base of the trunk. I have an intact trunk seal and the trunk shuts very snug- not loose and no rattles, yet the seal is at least 30 years old and is obviously not making contact all the way around. Thanks for the suggestions!
 
michael-king

michael-king

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Yes the air circulates back, another thing to check is the 4 okugs in the rear trunk floor .. They were originally metal but are often replaced with rubber ones, if they have perished ir are missing, they may a also be a point of entry for the fumes
 
hottigr

hottigr

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825
test drive

The new trunk seal did the trick- no more fumes in the cabin. The new seal from Rick is much stouter than the rubber only seal that was on there. The new seal has metal inside that helps the seal stick and conform to the curves. Just goes to show, just because something is still intact doesn't mean it's still doing it's job...thanks for the tips.
 
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