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Any suggestions on how to fix exhaust leaking at the head on a 24HP vtwin? I've replaced heads (separate reason), muffler, and gaskets. Also tried to add some high temp gasket maker. Exhaust gases are leaking out between the head and the muffler flange, no matter what I try. Any other suggestions?

Thanks,
Craig

Do you have a nice new exhaust gasket in there ?
Are you sure it is leaking where you think it is leaking ?

bertsmobile1 said:

Do you have a nice new exhaust gasket in there ?
Are you sure it is leaking where you think it is leaking ?

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bertsmobile1, thanks for you questions. Answers below.

I've tried with three new gaskets. It's leaking basically halfway between the two bolts that go into the head, from between the head and muffler flange (and gasket). I didn't torqued to spec the first time (and probably flattened the gasket a bit), so replaced the gasket and redid it with new gaskets and the proper torque. That didn't work. So I tried adding a little high temp gasket sealer and a new gasket set. That didn't work, so I replaced the muffler and used another new gasket set. Still leaks from the same place.

I'm positive it's leaking where I think. It's quite easy to feel the hot exhaust blasting out of that spot away from the engine. I suspect it's also leaking in the same basic area, but on the backside of the flange back toward the engine.That exhaust going toward the engine is my main concern. I replaced the heads because the value stem seals pushed out, leading to a broken push rod. The engine cooling gins weren't really plugged with grass or anything, so I suspect it was related to overheating due to exhaust blasting directly back on the engine.

Take a straight edge and check the exhaust flanges on the muffler. You probably find they are warped. Sometime you can file them back to flat, other times it requires a new muffler.

And of course the RTVs don't work; way too much heat and back pressure in that area. It is the customer here that tried using RTV on a head gasket, just made one heck of mess for me to clean up.

Was it leaking before you changed out the head and muffler?
Does it leak the SAME with both mufflers?
If you disconnect the plug wires and crank the engine can you still feel air blowing out at the leak point? If you do it is a blown head gasket.
Install a NEW exhaust gasket and run engine for about a half hour then carefully remove gasket and look for carbon tracking. If leaking you should see black or discoloration at the leak.

Hammermechanicman said:

Was it leaking before you changed out the head and muffler?
Does it leak the SAME with both mufflers?
If you disconnect the plug wires and crank the engine can you still feel air blowing out at the leak point? If you do it is a blown head gasket.
Install a NEW exhaust gasket and run engine for about a half hour then carefully remove gasket and look for carbon tracking. If leaking you should see black or discoloration at the leak.

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Thank you. The old muffler was leaking before replacing the heads (replaced both sides) and after. The new heads with the new muffler strangely leak in the same place. I'll double check for carbon.

Hammermechanicman said:

Sorry, I hit the wrong reply and don't seem to be able to delete this. Craig

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StarTech said:

Take a straight edge and check the exhaust flanges on the muffler. You probably find they are warped. Sometime you can file them back to flat, other times it requires a new muffler.

And of course the RTVs don't work; way too much heat and back pressure in that area. It is the customer here that tried using RTV on a head gasket, just made one heck of mess for me to clean up.

Click to expand...

I actually replaced the muffler already. The old one was a tiny bit warped on each flange. Seems dumb now, but I didn't double check the new muffler flanges flatness, but I'll give it a check. Thanks for the suggestion.

if the flange is a flat flange, a belt sander with a hard flat plate and an alum oxide belt is the easiest way to get a flat surface. Did hundreds of manifolds that way. Do a figure eight of lay the flange in each direction lightly Up down right left 45 45.