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Fri Jun 23, 2017 12:25 pm

Hey all,

Is doubling up on exhaust manifold gaskets a good idea or no?

I noticed the other that I had a small exhaust leak at the header flange at the #2 cylinder. I could see a gap between the gasket and the engine and figured something might have come loose and the exhaust ate away part of the gasket (which was recently replaced). Well I went in there today to replace it and the gasket is fine and there's a gap with the new one as well. Seems like the header isn't sitting flush with the engine and I can't figure out why. I loosened all of the connections on that header, tried moving it around and tightening that flange first but still no go. As a temporary measure I doubled up on the gaskets. It still leaks a tiny bit (at least, when cold, maybe the expansion on warm-up will seal it up), but it'll do until I can get in there and investigate more next week. I just wasn't sure if doubling up was a common thing to do or a bad idea.

New seal, you can see the gap still and where it had been leaking before:

With two gaskets it seems to be leaking from between the two gaskets:

The old gasket. It was leaking between the metal part and the engine:

Fri Jun 23, 2017 1:46 pm

Your exhaust flange is not straight or your head is pitted ( brah!)

Gotta make one or the other flat again....

Fri Jun 23, 2017 2:52 pm

Face the gaskets the same way so that the softer part does the sealing?

Fri Jun 23, 2017 3:10 pm

Metal side of the gasket is supposed to face the head. Are you sure its the gaskets leaking? Is that a possible pin hole on the pipe near the nuts?

Fri Jun 23, 2017 3:48 pm

Pull the pipe and place a straight edge across the flange. You will probably find that the ears have been bent a bit. Use a angle grinder or dremel to grind down any high spots.

Alternately, you might be able to go a long time by using JB Weld as a filler between the two gaskets. No promises. :cry:

Fri Jun 23, 2017 5:29 pm

I have belt-sanded exhaust pipe flanges to make them flatter for a better seal, and used double gaskets. I also heavily gunked all mating surfaces (flanges, head, both sides of each gasket) with Permatex Copper Spray-A-Gasket. Good luck!

Sat Jun 24, 2017 6:34 am

ALIKA T3 wrote: Your exhaust flange is not straight or your head is pitted ( brah!)

Gotta make one or the other flat again....

+1

How do you expect the gasket to work if the surfaces are warped? Take a file and straight edge and go at it. Do it right because that's the only way it will fix it right.

Sat Jun 24, 2017 7:15 am

Gauche1968 wrote: Metal side of the gasket is supposed to face the head. Are you sure its the gaskets leaking? Is that a possible pin hole on the pipe near the nuts?

With them doubled I have one with metal facing the head and one facing the header. No holes in the header, positive it's coming from there.

The pipes are the stainless RMW pipes a couple years old. The engine is <2 years old so I wonder how something got out of whack? Maybe when I hadn't the pipes off somewhat recently I somehow bent something. Not entirely sure.

Unfortunately I don't think I can get that whole header out to work on it without removing the rest of the exhaust, which probably won't happen in the short term as I'm on the road. I may be able to file it or something in place, or use sealant until I have the time/place to get the whole thing off.

The leak is really small and probably closes once the engine is heated up, no it's not incredibly urgent to seal it, but I would like to fix it a second soon as I can anyway.

Sat Jun 24, 2017 5:45 pm

I had a similar leak on the same cylinder and I put a stainless hose clamp around the flange/head juncture. It fits pretty well and does not repair the leak but it does help muffle it a bit if you find the noise distracting.

Mon Jun 26, 2017 9:07 am

campism wrote: I had a similar leak on the same cylinder and I put a stainless hose clamp around the flange/head juncture. It fits pretty well and does not repair the leak but it does help muffle it a bit if you find the noise distracting.

Thanks for the tip! Right now the noise isn't really bad at all. I can't even tell there's a leak by sound at this point. I also think the leak may seal itself as the engine warms and the metal expands, but I plan on checking the leak later after it's warmed up to see if that's true.

I head to Houston next week and then ship the van to Colombia so I'm honestly not sure I'll have the time to take the exhaust completely off to file/sand anything down before then. May have to get some exhaust sealant/gasket maker as a temp fix and then deal with it for good when I enevitably have to take the exhaust off for something else. I'll see how things unfold the next few days.

Mon Jun 26, 2017 2:44 pm

Well, turns out I can't use the soapy water trick when it's warmed up because it all sizzles/bubbles so much on the hot metal that I can't tell if air out of the leak is causing any of bubbles. Oh well. I'm going to take it off again tomorrow and see what I can do.

Mon Jun 26, 2017 4:27 pm

I would try them with both metal sides facing the head. That will give the softer side a chance to seal against the header as if you were only using a single gasket.

Mon Jun 26, 2017 8:12 pm

Thanks, that's a good idea. I'll give that a shot when I look at it tomorrow.

Mon Jun 26, 2017 8:37 pm

FYI, frustrated at poor joints at the cast iron Y, I tried doubling, and I tried NAPA's pricey exhaust joint goop to no avail. It just kept leaking. Finally, I took the parts to a buddy's machine shop and belt sanded them all flat. After my first 350 mile trip with the rebuilt engine and carefully tended to exhaust, I arrived home to a telltale pffft pfffft. Yep, something else is leaking under there I have no doubt. So it's a process with essentially no solution, apparently...

Doug

Mon Jun 26, 2017 9:14 pm

using a torque wrench to proper torque values during the initial install will avoid warped flanges...so if you manage to "unwarp" them, then replace the nuts, and studs and torque to proper values...unfortunately exhaust (and other) parts are usually over tightened, causing distortion to occur when the parts are heated due to dissimilar metal expansion rates...good luck, I wound up replacing all the exhaust and studs..(the studs weren't very cooperative)...
and then the retorque after 1000 miles and have had no more issues

Mon Jun 26, 2017 10:14 pm

Embossed metal gaskets will do a better job if the flanges are not flat than the composite gaskets you have. Doubling up of embossed gaskets seem to work particularly well in some cases.

Wed Jun 28, 2017 7:15 am

IdahoDoug wrote: So it's a process with essentially no solution, apparently...

Dang, that sucks! I won't get my hopes up then...
Unfortunately, being on the road right now I don't have access to a lot of tools (belt sander, etc.) or the luxury of taking the entire exhaust off and bringing the header to a shop to flatten, unless I have somewhere to stay.

My next attempt will be to use double gaskets, both metal sides facing the head as suggested, and using copper exhaust sealant between the gaskets and on either side.

I can't seem to find embossed gaskets, but if I can find some I'll pick them up.

I guess I never really thought about over tightening potentially causing warping. Anytime I've ever worked on the exhaust I've torqued them to spec, though it's possible that a shop I took it to a month or two ago might have overtightened...no proof on that.

Anyway, we'll see how today goes. Gotta wait 24 hours for the goop to cure, so I'll know tomorrow.

Fri Jun 30, 2017 11:24 am

Alright, well I made a valiant effort with doubled gaskets and the sealant. Tested it today and it appears there may still be a small leak, though not as bad. When I first started it up yesterday it definitely sounded loud like it had a big leak, but I think it may have been either really noisy lifters or something else from not running for a couple of days. I started it up this afternoon after sitting overnight and it sounds normal.

It's really hard to tell if the leak is there with the soapy liquid method because it always sizzles and bubbles up anyway from the hot metal, but I think it was bubbling more from around the gasket. It's small enough to where I can't feel any air coming out if I put my hand there, so I doubt it's going to cause any issues.

Maybe the solution is to overtighten the nuts/studs and hope it warps back into shape :lol:

Fri Jun 30, 2017 4:03 pm

blackglasspirate wrote: Alright, well I made a valiant effort with doubled gaskets and the sealant. Tested it today and it appears there may still be a small leak, though not as bad. When I first started it up yesterday it definitely sounded loud like it had a big leak, but I think it may have been either really noisy lifters or something else from not running for a couple of days. I started it up this afternoon after sitting overnight and it sounds normal.

It's really hard to tell if the leak is there with the soapy liquid method because it always sizzles and bubbles up anyway from the hot metal, but I think it was bubbling more from around the gasket. It's small enough to where I can't feel any air coming out if I put my hand there, so I doubt it's going to cause any issues.

Maybe the solution is to overtighten the nuts/studs and hope it warps back into shape :lol:

It won't bc it's warped the other way: it's concave rather than convex :wink:

Sat Jul 01, 2017 7:31 am

ALIKA T3 wrote:

It won't bc it's warped the other way: it's concave rather than convex :wink:

It was a pipe dream, but still a dream!!