Use exhaust assembly paste on OE muffler joints? - PeachParts Mercedes-Benz Forum

dogguy · #1 08-03-2015, 04:45 PM

In my muffler replacement post here last week (thanks for the replies), I neglected to include this:
Should a small amount of exhaust assembly paste be used on the two joints in addition to the clamps?

Refresher:
I am replacing the original M-B center and rear mufflers on my '83 300CD-T with Ansa OE mufflers.

I see that Wurth (I like Wurth) offers an Exhaust Assembly Paste (two attached images).

I'd appreciate the chance to read of the experiences of others about using (or choosing not to) paste. Thanks-

BWhitmore · #2 08-03-2015, 04:55 PM

The exhaust paste won't hurt -OK to use.

Mxfrank · #3 08-03-2015, 08:16 PM

I use a light coat on slip joints. Also on turbo flanges. Don't know if it makes a difference, but it certainly hasn't hurt anything. On stainless systems, it's a must.

97 SL320 · #4 08-04-2015, 01:58 PM

Are these slip joints with a u shaped clamp? I don't put anything on joints. The stuff drys hard and brittle so it will crack with any movement.

If you use regular u shaped clamps, place the edge about 1/4" from the outer pipe joint, this will allow the outer pipe to crush easier.

Try stainless steel band clamps like this http://www.apexhaust.com/wp-content/uploads/2010/07/HD_Premium_Exhaust_Clamping_Products_APEC0808.pdf However you will need to see if they have metric sizes if your pipes don't match a inch standard.

I've used the "good" flat band clamps on lots of industrial exhaust applications, they work just fine and are pretty much all you see on large trucks.

On the 2nd page, the "better" narrow band clamps are to be used only with slotted pipes. ( this style goes back decades.)

BillGrissom · #5 08-04-2015, 03:21 PM

A thin coat is fine. Most have glass beads that help seal once the carrier bakes away. Of course, you can't re-use or move the parts once set or you will lose the seal.

Maxbumpo · #6 08-04-2015, 03:31 PM

Interesting! Wish I'd tried this stuff when replacing the catalytic converter on my E300.

The second picture with the text seems a little contradictory. It says the paste hardens into a permanent seal, and then it says it prevents corrosion so dis-assembly is easy. Can't be very "permanent" if it comes apart?

I remember how pleasant it was to take apart the exhaust on my '85 wagon, much to my surprise. I had to remove it to replace the flex discs, and I expected a big fight but it came right apart at the joints. My '95 sedan was the opposite. One joint came apart just fine (it was two collars that pulled together and compressed on a one-time-use seal) but the other was a slip joint and it was not coming apart at all.

My inclination would be to use nothing, and then you should have an easier time getting the joints apart?

BillGrissom · #7 08-05-2015, 02:26 PM

The seal is "ceramic". It seals exhaust gas fine, but adds little structure. It is slightly porous, but soot soon clogs the pores. It is quite friable, so when you start twisting the parts it breaks up and falls out of the joints, like sand. That is why it is easy to remove and keeps the two metal surfaces from rusting together. "Furnace cement" is similar material. The highest temperature epoxy I have seen is 750 F, which wouldn't last in the exhaust under worst conditions. Normal epoxy ~250 F, silicone rubber ~500F. Any cement or sealant >750 F is usually ceramic.

Mxfrank · #8 08-05-2015, 05:48 PM

The other advantage is that you don't have to crush the pipe to get a good seal, which makes removal a great deal easier. If you were doing a stainless exhaust, you'd find that is difficult to get a seal without it.