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Old 06-08-2009, 02:59 PM   #1
kaisersouse
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Default changed header->cat pipe gasket...still have exhaust leak :(

So I did some exhaust work a while ago and neglected to get a replacement gasket to go between the cat pipe and the headers. Got one and installed it yesterday and I'm STILL having exhaust leak issues.

When I replaced it I disconnected both pipes and then scrubbed them clean of leftover gasket, rust, etc. Put the gasket on and then reassembled (two-bolt flange, I used new hardware) and tightened until I couldn't tighten it any more.

I then sprayed the entire area with lots of WD40 (so it would burn/smoke) and then started the car. Let the WD40 start burning off and hit the gas...I got to watch all the smoke that was around the connection get BLOWN TOWARDS THE FRONT OF THE CAR. You can hear noise and a hissing sound when you hit the accelerator and the noise comes from that connection.

Since I've only driven it for 2 hours with the new gasket...can I take it apart and add some liquid gasket maker stuff* to make it shut up? If not....wtf can I do without buying a new exhaust? Did I install the gasket wrong? It looked pretty brainless so I don't know if I was supposed to heat the pipes up first or do some kind of odd vehicle mating-ritual (idle for 20 minutes, run WOT for 10 seconds...something like that)



* yes, the high-temp stuff. I have these sitting in my garage unused

http://joinleader.en.alibaba.com/pro...ir_Sealer.html

http://joinleader.en.alibaba.com/pro...ket_Maker.html

My gut says go with the gold stuff that can tolerate 2000 degrees
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Old 06-08-2009, 07:39 PM   #2
JamesWilson2
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You can actually over-tighten those so that the gasket is crushed a lot and will develop leaks from not being able to expand/shift while heating up and cooling down. Find the OEM spec for the bolts, and use that. I'd also use an OEM gasket, I've had tons of exhaust leak issues solved by going to the dealer for the right gasket. I do cheat though, and spray Permatex Copper super-high-temp gasket maker (for exhaust manifold gaskets...copper, comes in a spray can). Let it get tacky first before mating.
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Old 06-08-2009, 09:37 PM   #3
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Quote:
Originally Posted by JamesWilson2 View Post
You can actually over-tighten those so that the gasket is crushed a lot and will develop leaks from not being able to expand/shift while heating up and cooling down. Find the OEM spec for the bolts, and use that. I'd also use an OEM gasket, I've had tons of exhaust leak issues solved by going to the dealer for the right gasket. I do cheat though, and spray Permatex Copper super-high-temp gasket maker (for exhaust manifold gaskets...copper, comes in a spray can). Let it get tacky first before mating.
this.
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Old 06-09-2009, 09:18 AM   #4
kaisersouse
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Most excellent replies. Thats precisely the info I was seeking. Thank you!
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Old 07-09-2009, 01:04 PM   #5
kaisersouse
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BAck up again

Using new gasket plus the copper exhaust sealer helped reduce the mayhem by 50% or so. Now you hear a slight hiss nromally and a gutteral BWAAAAAAAH under acceleration (before it was yelling all the time).


Theory I want to try:

Buy 3 new gaskets, sandwhich them together with a mighty helping of exhaust sealant between them as a sort-of "glue". Clamp them to the work bench overnight to make them all smooshed together and then replace the regular gasket with my frankengasketspacerthing. Possibilty for success or guaranteed comedy of errors?

EDIT: if this works out im trademarking/copyrighting "frankengasketspacerthing" so back off! (kidding)
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Old 07-09-2009, 02:01 PM   #6
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you may have to unbolt the whole thing and put all new gaskets and tighten it all up a little at a time, in a rotating pattern----like tightening a wheel
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Old 07-09-2009, 02:18 PM   #7
kaisersouse
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Quote:
Originally Posted by Uncle Scotty View Post
you may have to unbolt the whole thing and put all new gaskets and tighten it all up a little at a time, in a rotating pattern----like tightening a wheel
The issue (that I forgot to mention) is that the weld where the flange met the cat pipe had rusted out a while ago so I had a new flange welded on. The new one is like .5% off on rotation so it doesnt really line up perfectly. Its either cut it, have it re-welded and hopes its right, or apply some yankee ingenuity and frig-rig it together with gaskets and snot.

When I chaged it the first time I unbolted it and slid it out from under the car to work on it because I don't have a lift and I've gotten slightly fat since quitting smoking so it was easier to jsut slid it out, do what I needed to do and put it back. Thats when I noticed it wouldn't hang right without loosening the headr/cat flanges, hanging, then retorquing.


CNs: the replacement flange rotation is off a bit so its not sealing and I'm trying to just shut the damn thing up without cutting/welding again.
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Old 07-11-2009, 04:16 AM   #8
bue car
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sand the flange down?
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