I need some advise on which type of exhaust gasket sealant i should use between the downpipe to the cat then between the cat and exhaust. I usually use permatex copper high temp sealant with a metal gasket but still get an exhaust leak. Please name some brands and if you got pics of the product, thanks.

 

You shouldnt use sealent before the cat as it could cause chunks of sealent to break off inside the pipe and sit on the cat core, this then superheats due to being denser than the cat and eventually kills the cat, iv seen it lots of times, use a compression gasket will a metal ring round the inside, these dont need sealant.

 

If I don't use any sealant i have an exhaust leak. I brought my car to a local muffler shop (golden auto) and they used something in an orange bottle for exhausts. It worked great! and i wish i knew what it was.

 

I've use the copper high temp RTV and it toasted very quickly. Others have used it and had good success.

I wouldn't worry about it getting in the cat as long as you don't use too much.

Dave

 

Look into some of the Rutland high temp water base ceramic sealants:

http://www.rutland.com/maintenance_h...7C_78_78F.html
can be used to make a gasket


http://www.rutland.com/maintenance_html/77E_78E.html
more of a gasket sealant

 

Really, you shouldn't use sealant on the exhaust gaskets. The mating surfaces should be clean and flat, and the gasket should have some "give" to it.

If you're having leaks, either the fasteners aren't working properly (they're siezing and not fully seating on the flange), the flanges aren't true, or the gaset is shot.

IMHO, using sealant on exhaust isn't a good idea. That makes a failure point - it's easier for pressure to blow the sealant out instead of the gasket. Not to mention it makes a mess, gums up the flange for future removal/reinstalls, and is simply unnecessary.

Also, cheap exhaust components (like Ebay downpipes and midpipes) many times don't line up properly. I experimented with an Ebay midpipe - the flanges weren't angled right, and it wouldn't seal properly at the top of the flange, resulting in a leak.

Dale