TheSamba.com :: View topic - Has anyone used RTV to seal exhaust flanges?

Thu Apr 13, 2006 5:32 am

Good Friday is Bus Friday for me. I will be reassembling the exhaust on my 77 Westy. Karl has sent me an awesome set of u-pipes and heat exchangers. I have the so-called “squishy” gaskets and have spent way too much time filing down the flange mating surfaces to get them flat. The trouble spot will be the flanges at the end of the manifold coming off the head. They are still on the Bus. I will attempt to file and hammer them flat. There isn’t much of a mating surface. Here’s my question…. Has anyone used hi-temp Red or Copper RTV on exhaust flanges with success? I have some exhaust assembly paste but that stuff turns hard. I don’t want it crumbling down the road and causing an exhaust leak. What has your experience been?

This is the last big project keeping me from getting it back on the road.

Thu Apr 13, 2006 6:13 am

It may last a week or so, then it will turn to powder from the heat.

Thu Apr 13, 2006 6:39 am

I have had very good luck with Permatex Ultra-High Temp copper RTV, it has a dull coppery look, not bright orange, and is suitable for oxygen sensor installations etc. It stinks like hell as it cures, not a nice pungent aroma but a mean stink.
Colin

Thu Apr 13, 2006 6:46 am

That was the same stuff we tried on the cheap empi exhaust (cheap assed thin gaskets from empi) I had.
Lasted about a week, just got to hot.

Thu Apr 13, 2006 6:57 am

I have the metal "sandwich" gaskets. I'm looking for a way to seal up any small gaps along the mating surface. By small I mean something in the order of .006" or so. The exhaust paste that I bought is by Wurth. They seem to have a good reputation for quality products. However, I've never used this paste before.

Thu Apr 13, 2006 9:17 am

This is what I use on the gaskets, including the head-to-pipe. It does not vaporize, and was still pliable when I removed the muffler.

Thu Apr 13, 2006 9:57 am

dr. no wrote: This is what I use on the gaskets, including the head-to-pipe. It does not vaporize, and was still pliable when I removed the muffler.

That's good to hear. I only want to do this once. Hopefully I'll have a great testamonial to Wurth exhaust assembly paste.

Thu Apr 13, 2006 10:19 am

Amskeptic wrote: I have had very good luck with Permatex Ultra-High Temp copper RTV, it has a dull coppery look, not bright orange, and is suitable for oxygen sensor installations etc.

I put on a nice custom exhaust last year and combined with the Permatex RTV AND a metal gasket its worked just great! About 2000 miles and its still hanging in there.

The EMPI exhausts just suck so bad they are a problem in and of themselves. If you do a search you will find me ranting and raving about my one time experience with EMPI exhausts and how I learned never to buy anything EMPI again.

Thu Apr 13, 2006 12:04 pm

When I re-assembled my engine last September, I decided to re-use my old heat exchangers rather than buy new ones. The flanges where the crossover pipe bolted to were getting pretty thin, but like you I filed and filed and filed until there was a more-or-less flat mating surface. But there were still hollows in the flange which I wasn't happy with.

So: JB Weld to the rescue. I took the Dremel to all the rusty bits in the flange until there was a good surface to bond to. Mixed up a small quantity of JB Weld and spread a thin layer over the holows in the flange. Then I laid a sheet of wax paper over the goop and clamped a chunk of flat sheet aluminum or steel to the flange. Let cure for 24 hours. Upon removal of the wax paper, I only had a little bit of dressing with the file to get a good mating surface.

No leaks so far... [-o<

Thu Apr 13, 2006 12:45 pm

SlowLane wrote: So: JB Weld to the rescue. I took the Dremel to all the rusty bits in the flange until there was a good surface to bond to. Mixed up a small quantity of JB Weld and spread a thin layer over the holows in the flange. Then I laid a sheet of wax paper over the goop and clamped a chunk of flat sheet aluminum or steel to the flange. Let cure for 24 hours. Upon removal of the wax paper, I only had a little bit of dressing with the file to get a good mating surface.

No leaks so far... [-o<

That may be my plan B. At least this time, if I have to take the exhaust apart again I won't have to soak, twist grind and heat to get the bolts off.