Exhaust Manifold Gasket

[Dougimes]

Question,

About 6 months ago, I replaced an exhaust manifold gasket. The gasket has since failed. I torqued the bolts to 25 ft lbs, but over time, I got blow thru on the bottom of the #2 cyl exhaust, between the pipe and the gasket.

I am getting ready to do it again- here are a few questions-

1. Has anyone used hitemp silicone sealant, the red stuff"
2. Manual says torque to 25, can I go a little higher?
3. has anyone ever doubled up on gaskets, use 2 exhaust manifold gaskets to provide a little more takeup assuming the surfaces are perfect.

Thanks for help. I hate repeating work.

[Don Cavey]

I've not replaced my exhaust manifold yet (typically cracked in the usual place) and don't look forward to it. That said, You might want to lay that manifold on a flat surface if you can find one big enough. Or for that matter, try test fitting it against the head with no gasket to see if it is warped. That seems to be what is going on to me.

As for double gasket or over-tightening it, I think you will invite a cracked manifold. They don't like to be stressed very much. If I were to try something, it wouldn't be silicone because I don't think any of them would survive the heat of exhaust gasses. You might try that muffler sealer paste. It looks a lot like joint compound and is used to seal exhaust pipes. Kinda like furnace cement.

[brute4c]

Silicone wont survive there for sure...

Doubling the gasket will leave leak problems...

I would check for problems between the head and manifold...casting irregularity or head problem in that area...

You might tighten them to 30 lbs but I wouldnt go more than that...doubtful if 25 to 30 lbs would make enough difference to seal it up for you...

The muffler sealer stuff might work or even actually the furnace stuff...

I will guess the manifold is the leak source...might have to try to find another one to seal it up good...let us know what you find when you get in there...

[Don Cavey]

Truthfully, I believe the manifold is warped. Do you have a straightedge that you could set against it? Or is it possible to mate it to the head with no gasket and all surfaces cleaned to look for warpage?

[jeepdan]

Question,

About 6 months ago, I replaced an exhaust manifold gasket. The gasket has since failed. I torqued the bolts to 25 ft lbs, but over time, I got blow thru on the bottom of the #2 cyl exhaust, between the pipe and the gasket.

I am getting ready to do it again- here are a few questions-

1. Has anyone used hitemp silicone sealant, the red stuff"
2. Manual says torque to 25, can I go a little higher?
3. has anyone ever doubled up on gaskets, use 2 exhaust manifold gaskets to provide a little more takeup assuming the surfaces are perfect.

Thanks for help. I hate repeating work.

Don is on the right on.
First, check the manifold gasket surface with a straight edge, could be warped or rusted .

Is the rest of the exhaust system well supported in the original locations?
Especially with the clamp at the transmission? Very important!

Manifold nuts are to be retorqued at every tune up.
That might not be soon enough after a fresh gasket change.

I'm going to retorque mine today

[jeepdan]

Manifold nuts are to be retorqued at every tune up.
That might not be soon enough after a fresh gasket change.

I'm going to retorque mine today

Thank you for bringing this subject to my attention.

I found all of my exhaust manifold nuts loose. Some required almost a 1/2 turn to get back to 26 ftlbs of torque.
This, after less than three hours running time, after the initial retorquing at 1/2 hour run in.

I can see that I need to check all fasteners for proper torque.

[Don Cavey]

Dan, that neat, clean engine ↑ makes me sick! Not really, it looks good, real good and I wish I were able to get to that state.

I had another thought. If you don't have a straight edge but maybe a granite counter top, that is usually straight.

As Dan mentioned, you MUST have the clamp at the transmission mount secure. My truck didn't have one (Didn't have exhaust!!!) and I got one.

Hope this all helps...

[militarypotts]

Hey Dan, is that a brand new exhaust manifold, or did you blast it and paint it? Having nice clean bolts like that sure is pretty.

[jeepdan]

Hey Dan, is that a brand new exhaust manifold, or did you blast it and paint it? Having nice clean bolts like that sure is pretty.

It's the original manifold.

After grinding off all of the casting flash, and sandblasting it, I used Calyx paste on it.
http://www.eastwood.com/calyx-manifold-coating.html
It's the first time that I have used it, so I'm not sure how durable it is. But it will be easy to reapply (smear on with a tooth brush, and wipe with a rag)

And yes, replacing all of the manifold studs, and nuts the way to go.

Picture after grinding, before sandblasting.

[Dougimes]

Dan,

Why am I not surprised that you have a pristine hardbound service manual. Your work is beautiful, I'm inspired.


I have good direction on this, manifold off, check for flat, single gasket, new studs, torque to 30 often, make sure exhaust is well supported

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