Is there a 'permanent' fix for a manifold leak?

[kcducttaper]

I just rebuilt my motor and whoever rebuilt it or took it apart before me (it was a salvaged engine at one point) broke off some of the exhaust manifold bolts in the heads. There seems to be one leak in particular that's extra noisy and the gap between the manifold and the head is about maybe 1/8" or so. I'm looking for some sort of putty or wrap to more or less permanently fill that gap. I stopped by the car parts place and reluctantly got some "HighHeat" JB weld that advertises it works on manifolds. After my research at home, my suspicions were true that the HighHeat stuff simply isn't rated for hot enough and will fall off fairly quickly. Is there another more permanent solution to plug the gap other than taking a welder to it?

[Stealthee]

Only way to properly fix it is to drill out the broken exhaust studs and replace them.

[kcducttaper]

At this point, I'm not necessarily trying to "properly" fix it as it's a 20 year old minivan that I'm just trying to squeeze a couple more years out of. I mostly just want to plug the leak enough that it won't send much exhaust gas into the passenger compartment and that I can't hear the leak anymore. If that takes simply welding the header to the head, I'm down with that. The only reasons I can imagine needing to disconnect the exhaust for would pretty much require the engine to be removed again. If that;s the case, I can cut open the weld and get new heads or re-thread everything. Whoever did this before me really screwed it up. Some holes have bolts broken off in them; some are completely stripped out; etc. I've probably only got 2/3 of the bolts "properly" in there anyways, but as long as it's not making loud exhaust noises or shoving exhaust into the cabin, I'm ok with it.

Every sort of putty I'm finding has reviews that say it cracks and falls off relatively quickly. The motor is in the car now, so I'm not too excited to have to drag the whole engine out again to take out a bolt. I may have to make a shim to squeeze in there and carefully weld it up to the exhaust manifold or something, which could be tricky considering the manifold is probably cast iron.

[Stealthee]

I don't know what kind of car you have, but trying to weld has a massive potential to do nothing but destroy the head.

My motto has always been, do it right, or don't do it at all. If an engine pull is required it is not something that takes days. You can have the engine out, studs drilled out, and everything fixed in less than a weekend.

[Crvett69]

the manifold will heat up at a different rate than the heat so will rapidly break any weld you try to to between the manifold and head. best way it to pull manifold off and try and get broken bolts out. if your lucky some of the part will still be sticking out of the head and you can heat them up with a torch and unscrew them. another possibility is to get new gaskets, put 2 together and coat them with high temp silicone to seal the gap then let it cure the recomended time. may or may not fix your leak permanatly but might work for a while

[vgames33]

If you have room, pull the manifold back and stack a couple of gaskets on top of each other. It might not last forever since you are missing bolts, but this did seal up my warped headers pretty well.

Welding or epoxy won't work unless the heads and manifold are the same material, and even then I doubt that it would last very long due to expansion rate and vibration. The epoxy is rated for fixing a cracked manifold.

[kcducttaper]

I can't say I'm terribly surprised that welding probably won't work well.

I've heard of stacking 2 gaskets in there, which seems like it should work nicely for my application presuming I can get it to stay in place. I've also heard of some people stuffing it with red RTV or Copper RTV and getting decent results from that. Thoughts?

[vgames33]

If you're dead set on a bandaid, I'd go for stacked gaskets coated in copper or red RTV. Since the bolts are missing you run the risk of blowing out the gaskets, even if it seals up due to the lost clamping force. The sealer will help hold everything in place.

[Stealthee]

As vgames said what you intend on doing is nothing more than a bandaid fix. If you want a real permanent fix, you are going to have to pull the manifold and try to get the broken studs out.

[vitalmuncie]

if there is anything of the stud protruding out of the head you would be better off with channel lock pliers than vice grips. permatex may work on intake leaks but it will just burn off the exhaust.

[tomj76]

It sounds like you have the common problem of steel bolts frozen into aluminium. The only solution is to pull the head(s) and have the broken studs removed.

You don't say anything about the make/model, but since it's a minivan, I'd almost guarantee that the heads are made from aluminium. You might be able to take the gasket doubling approach. There are adhesives that are meant for very high temperatures (i.e. >2000 degF) that you could use. For example: http://www.cotronics.com/vo/cotr/ca_metallic.htm

FYI, if you want to weld the exhaust manifold (header) to the head, you can't weld cast iron (normal composition of exhaust manifolds) to aluminium. It's just not possible. The only approach available might be to braze the aluminium to the iron. I'm not sure this is any easier than removing the studs since brazing it done at a high enough temperature that it could warp the head.