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Seal a leaking exhaust manifold

Brian1973

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So I went through an "exhausting" manifold repair of old rusty studs and worn gaskets involving a torch and drill. Have new grade 8 bolts and all seems great except for one leaky spot and I suspect it's slightly warped at the head as I tried to repair it in the past after machining the manifold flat. Ideas on how to seal the spot leaking? Was thinking some muffler repair goop but fear that will eventually blow out? double gasket? It's just one spot on the last cylinder on the driver's side, but it's blowing towards the spark wire and suspect I will begin getting misfires as previously was. Have a piece of sheet metal around the plug boot but would like to solve this!!!
 


RonD

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I would look for used drivers side manifold to replace that one.
But if it is the head then that probably wont help

Yes, you may want to try double gasket on that side.

High temp sealant can work but as you said it usually is just temporary because the metal in the head and exhaust expand and contract at different rates when they are heated up and cool down, gaskets can absorb those changes, if a sealant hardens then it can't and will start to leak.
Use sealant directly on the head, not manifold, head is cooled internally so won't expand and contract as much as manifold metal will.

So, head---sealant---gasket---manifold
Assuming head is the problem
 
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Brian1973

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I had a spare manifold from another engine. Same issue. Definitely head side issue. Thinking this stuff will harden and blow out? -https://www.amazon.com/gp/product/B000BOAZM8/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

but like that it's for 2000 degrees

only for 650 degrees but maybe this would be more suitable? -https://www.amazon.com/J-B-Weld-31314-Temperature-Silicone/dp/B00ID8IUJY/ref=sr_1_1?s=automotive&ie=UTF8&qid=1481916360&sr=1-1&keywords=high+temp+exhaust+sealant
 

Brian1973

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If going double gasket route, how about cutting the 2nd gasket so only the portion around the last cylinder (trouble spot) is double?
 

Brian1973

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or maybe, just take a tiny section of the 2nd gasket for the trouble spot, use sealant to attach it to the 1st gasket and put together and pray? :dunno:
 

RonD

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I wouldn't cut the double gasket

I am assuming from the description the leak is occurring because the head is not flat at that cylinder, so flat manifold and flat gasket is still leaving a small gap.
A second gasket "may" be able to seal that gap but if it is too deep or narrow then it won't.

The sealant, any type, is used to fill those uneven spots so the flat gasket and flat "part" can get a good seal on the uneven part.

You are there so can eyeball the possible problem, possibly use a straight edge on the head port to see where the problem is
 

Rearanger

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Thinking this stuff will harden and blow out?
Back pressure at manifold should be around 1-3psi. I'm not thinking there is enough pressure to "blow out".

Definitely try to locate depression. What have you got to loose?
 

Brian1973

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Thanks RonD! I'm guessing I will try the permatex stuff (2000 deg.) first, although I fear it will not be flexible. If that doesn't hold, may try the JB Weld hi temp (650) stuff, since it may be more flexible, but guessing it gets hotter than 650 there? Appreciate your knowledge!

Thanks Rearanger for the added input... funny you mention back pressure. Seems as I repaired this ongoing issue recently, found my cat was clogged so for the time being, knocked the innards out. The back pressure must have been enough that I was getting all kinds of exhaust pressure adding to the demise of spark plug wires through multiple blowouts of the manifold gasket and the y-pipe to cat gasket. I'm guessing my back pressure might be even lower than what you suggested now?

Change of subject but does anyone know if I could get something for the inside precious metals I ziplock bagged from the cat? Or at least give to someplace that can reuse it???
 

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