Leaking muffler flange

[jsoderbe]

Hi,

I am not sure what I am doing wrong; I have had a lot of problems with leaking muffler flanges, meaning the connection between the heat exchangers and the muffler.

I have really nice HEs, a really nice original muffler, and new copper gaskets. Still it leaks up and down on both flanges! And both of them are tight left to right, where they are bolted together.

Any thoughts? Have I tightened them too much? Warped flanges?


Regards,

Johan

[cdrik915]

Try to screw one side and after the other side.

I had the same problem with ssi Dansk & muffler.

[schumicat]

I've heard of people using two gaskets. I've never had to do that.

[MMiller]

Originally Posted by schumicat

I've heard of people using two gaskets. I've never had to do that.

This is what I have done on my car. SSI and Bursch set up but it does not leak with them doubled up

regards,

Mike

[Bob Kontak]

I have read where copper gaskets are a culprit. I bought a Fabspeed pre muffler to replace my cat on my 81. Could not get it to seal with their copper gaskets at the crossover pipe from the stock exhaust headers. Mind you, the flanges are a little beat up over the years.

I ended up using the non copper gaskets and put some of the muffler sealer sourced from a local store on both sides of the gasket and that did the trick.

It has lasted a few years now so I believe if there is a decent and tight fitting and the sealer is in between, it does the job. I think if there is movement it will just fall apart.

[Rich Lambert]

I had the same problem on my '66. I have 2 different mufflers I rotate on and off and neither of them would ever seal tight. I tried leveling the mating surfaces using various methods multiple times and none of that helped.

As a last resort, I went to an auto parts store and was going to buy some kind of silicone seal to use...even though that has never worked for me on any vehicle exhaust in the past. When I got to the counter, the guy said, "You don't want that crap" and suggested this stuff Remflex Exhaust Header / Manifold Gaskets . I bought the DIY 6.5" x 11" sheet and cut my own gaskets (Top Tip: a drill press and hole saw is really handy here). That's enough for 3, maybe 4 sets of gaskets. Be careful handling the cut gaskets as the material is kind of fragile. I had to re-make one of them when I damaged it during installation.

Last winter I put the "quiet" muffler on just to test the gasket stuff out. The car sounded better and backfired less. I took it off last weekend to put on the "not so quiet" summer muffler and the flanges had been sealed completely for 6 months...no leaks!!! The summer muffler has also never sounded better...no leaks!!!

I'm always blown away when something actually works as advertised and highly recommend this stuff.

Edit: one other thing I learned...tighten the flanges first, then the clamps, and don't reef on the clamp bolts, just snug them up.

[tobluforu]

Originally Posted by Bob Kontak

I have read where copper gaskets are a culprit. I bought a Fabspeed pre muffler to replace my cat on my 81. Could not get it to seal with their copper gaskets at the crossover pipe from the stock exhaust headers. Mind you, the flanges are a little beat up over the years.

I ended up using the non copper gaskets and put some of the muffler sealer sourced from a local store on both sides of the gasket and that did the trick.

It has lasted a few years now so I believe if there is a decent and tight fitting and the sealer is in between, it does the job. I think if there is movement it will just fall apart.

Before I went to ssi's I had leaky muffler flanges. I went down to the local muffler shop and they matched the flange with some gaskets off the shelf. These too were non copper and had about an 1\8 inch more meat on them. Problem solved, but use high temp red sealant as well.

[aston@ultrasw.c]

I have had good luck with these:

Exhaust Flange Gasket - 2 Bolt Exhaust Flange Gasket Vibrant Performance

[jsoderbe]

Hi Guys,

Excellent advice, as usual! I went with two gaskets, using the old and the new one. Then I put mounting paste all around them. Now it is tight and nice!

But, with these quiet I found out that I still have leaks at the head to HE flange. I have no idea what I am doing wrong here. New gaskets, new nuts, and they seemed to line up well.

I have experienced the same problem before, on a 3.0 SC with back dated heat. Then I solved it with an extra washer or two, since the nuts was to narrow for the exhaust studs.

However, I believe I shouldnt have that problem here? Any thoughts?


Regards,

Johan

[DRACO A5OG]

Brother Rich,

Not sure if you are still around but how is the REMFLEX holding up so far?

I have leaks at my crossover to cat.

TIA,

Jim

Originally Posted by Rich Lambert

I had the same problem on my '66. I have 2 different mufflers I rotate on and off and neither of them would ever seal tight. I tried leveling the mating surfaces using various methods multiple times and none of that helped.

As a last resort, I went to an auto parts store and was going to buy some kind of silicone seal to use...even though that has never worked for me on any vehicle exhaust in the past. When I got to the counter, the guy said, "You don't want that crap" and suggested this stuff Remflex Exhaust Header / Manifold Gaskets . I bought the DIY 6.5" x 11" sheet and cut my own gaskets (Top Tip: a drill press and hole saw is really handy here). That's enough for 3, maybe 4 sets of gaskets. Be careful handling the cut gaskets as the material is kind of fragile. I had to re-make one of them when I damaged it during installation.

Last winter I put the "quiet" muffler on just to test the gasket stuff out. The car sounded better and backfired less. I took it off last weekend to put on the "not so quiet" summer muffler and the flanges had been sealed completely for 6 months...no leaks!!! The summer muffler has also never sounded better...no leaks!!!

I'm always blown away when something actually works as advertised and highly recommend this stuff.

Edit: one other thing I learned...tighten the flanges first, then the clamps, and don't reef on the clamp bolts, just snug them up.

[Joe Bob]

While double gaskets and gasket dope works in many cases it's a band-aid. Putting a straight edge on each surface and checking flatness of the surfaces is best.

Anything bent can be heated with a MAPP torch and straightened with Vise grips or channel locks with a cheater bar. Sometimes it can be cleaned up with a metal rasp if the problem is clinkers from a lazy fabricator left on the mating surfaces.

OR....and this is surprisingly cheap. A good muffler shop will fix you up ricky tick.

[DRACO A5OG]

Brother M,

Thank you so much!

Just trying not to remove the exchangers but I think that is the best route and take it my local muffler shop or Vellios.

J

[Rich Lambert]

Originally Posted by DRACO A5OG

Brother Rich,

Not sure if you are still around but how is the REMFLEX holding up so far?

I have leaks at my crossover to cat.

TIA,

Jim

Jim, still holding up and still not leaking.

[DRACO A5OG]

Oh good to know.

I am still going to have the flanges re-surfaced just to get the pitting out from the previous seal being stuck on as it will not help being there.

I ordered the sheet of REMflex. Hey, extra insurance, a leaking flange just causes havoc on the O2S readings and AFR.

[RichardNew]

I've had good luck with Permatex Ultra Cooper Maximum Termperature
Silicone. Sometimes I don't even bother with a gasket. Just make sure you follow the directions exactly.



Richard Newton
Historic Racing Images

[DRACO A5OG]

Update, so I had a free day Yesterday and decided to prep my Euro Pre-Muffler for install. Went to HD and bought the Absolute Black piece of Granite Tile, 80 grit 3M sandpaper sheets then to HF to pick up a 4" tile Circular Saw and Blade Set.

Cut the tile into a 4X8" piece it, left a 4X4 piece too

So, I used the 4X4 and verified with a straight edge to gauge the mating surface of all three fittings, yeap, I see day light. No surprise, I knew there was gap but thought new gaskets would seal them, NOT. Just to make sure it was not dirt or carbon build up. I used the 4X8 with sand paper and gave it a once over ( well 10 times until I saw bare metal )

This is what I found:


Confirmed Leak Areas.

So I started with the collector, Went well, took a while but all pitting was removed, I did not want to go too low as it needed that lip to compress the new gasket. Glad I did this, I noticed water dripping from that fitment when I was breaking her in after the first 20 minutes of initial engine break in run at 2000 RPMs.


It was pitted, like the flanges.

...and now the flanges after hand sanding for a very very long time.


In the end, I sprayed some High Heat, Caliper/Engine primer rated for 2000F, then re-sanded it for hi/lo spots. Mating surfaces for the gaskets are FLAT. I did notice the upper portion of the oval flange was a bit lower (thin layer of primer), but that was due to heat damage from the years of leakage I really did not want to cut any more as there was plenty of mating surface now.

Now to tackle the flanges on the car, oh the joy

Side note, I did find in the hot rod section, a copper 2.50" ID collector with crush inner lip at the FLAPS, comes in a two pack. I will give that a try while waiting for the REMFlex. I have new flange gaskets on the shelf.

[DRACO A5OG]

Oh yeah, here is what it looked like on the gasket

obvious leakage

[bigel]

Originally Posted by DRACO A5OG

Brother Rich,

Not sure if you are still around but how is the REMFLEX holding up so far?

I have leaks at my crossover to cat.

TIA,

Jim

Draco, how do you diagnose to find you have "leaks at you crossover to cat"?

[DRACO A5OG]

I connected my sniffer from my LM2, I dialed in the AFM to read 14.7:1 Stoic for a smog check.

Good, you would think but when I measured off of my O2S using my DVM at the same time as the LM2. it read RICH. So basically, I had an exhaust leak before the O2S causing a lean situation and O2S was tell my car to richen the mix, dumping fuel, causing the voltage reading to go close to 1.00 volts ( 0.995 ). If no leaks and adjusted AFM to proper 14.7 AFR, it should be around 0.45 volts.

I suspect, the leak at the collector end gave another false reading at the LM2

Pic above is the actual evidence of leakage.

Honestly, if you do not constantly use your test pipe every 2 years like I do then you should be okay.

[bigel]

Originally Posted by DRACO A5OG

Honestly, if you do not constantly use your test pipe every 2 years, like I do then you should be okay

Draco say what?