Changing exhaust/intake manifold gasket - tips?

1941 - 1945, MB, GPW Technical questions and discussions, regarding anything related to the WWII jeep.
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Daegan
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Changing exhaust/intake manifold gasket - tips?

Post by Daegan » Thu Jun 22, 2017 2:58 am

Hi all,
I need to change an exhaust/intake manifold gasket which seems to be breaking up, and exhaust is leaking from it. I've started spraying the manifold studs/nuts with WD-40 to hopefully loosen them, and am now considering two main issues:

1. What is my best chance of removing the nuts without breaking a stud? Should I try using the heat/ cool / heat & go-for-it method I've seen discussed here, or keep adding the WD40? A few years ago I had to replace a cracked manifold, and broke a stud, which I don't want to do again. The nuts are regular steel, and I can't remember whether I used copper anti-seize last time - hopefully I did!

2. Can I replace the gasket without separating the intake & exhaust manifolds, or do I need to risk more breakages by separating them? I read a post here that suggested you can crack an ear if you re-tighten the manifolds when fixed together - is there a way around this? Further - is it possible to do this job without removing the manifolds from the exhaust coupling - is it flexible enough to simply pull the assembly back, clean, fit the new gasket and reassemble?

Many thanks all - I've always greatly appreciated all the excellent advice here.


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JIMN
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Re: Changing exhaust/intake manifold gasket - tips?

Post by JIMN » Thu Jun 22, 2017 3:45 am

Don't use wd40, that is just a lubricant. Use a penetrant like PB Blasters.
I wouldn't worry too much about breaking a stud. Usually either the nut or stud will turn especially if you have had them out before. Just try it first before applying heat.
I always remove them together. Never had a problem.
Yes the exhaust will pull away.
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Re: Changing exhaust/intake manifold gasket - tips?

Post by Joe Gopan » Thu Jun 22, 2017 3:58 am

And use caution that the coarse portion of any replacement studs is not longer than the originals, especially those stud positions that share a cylinder bolt hole.
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Re: Changing exhaust/intake manifold gasket - tips?

Post by Wolfman » Thu Jun 22, 2017 4:49 am

I suppose it is possible to change a manifold gasket without removing the exhaust pipe. Be sure the block and manifold gasket surfaces are clean.
Also need to check exhaust and intake gasket surfaces with a straight edge to be sure they are flat and flush.
One reason the manifold gasket can blow is the exhaust section warps from long time heating and cooling. To just replace the gasket won't solve the problem. also one reason the ears break. Trying to pull a warped manifold down puts excess pressure on it and it breaks. Cast iron is not very flexible and brittle. Especially with age.
Loosening the exhaust manifold to intake joint on installation might help a little but still won't cure a warped manifold. Disturbing that joint opens the door for more leaks.
PB blaster is on the bottom of my list. High end is Aero Kroil. A little pricy but works really well. What I have found that I really like is a WD-40 product called "Rust Penetrant". Gives Kroil a run for it's money. The Rust Penetrant is a quickie. Spray it on and it goes to work immediately but soon evaporates, where Aero Kroil is long and slow. Works fast but also has holding power and will penetrate slowly over time.
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Re: Changing exhaust/intake manifold gasket - tips?

Post by Daegan » Thu Jun 22, 2017 5:38 am

That's very helpful, thank you all for your advice, which I will follow. I looked into penetrants over here in the UK - we don't get PB Blaster or Kroil, but can get the WD40 rust penetrant. It seems that something called Plus Gas is also well thought of over here. Someone somewhere suggested that Plus Gas is primarily kerosene which is interesting, anyway it seems to work.
Thanks again chaps.

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Re: Changing exhaust/intake manifold gasket - tips?

Post by dinof » Thu Jun 22, 2017 6:01 am

My back bolt was leaking out Prestone when I first assembled everything so seal that bolt good in case you forgot about that one!
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Re: Changing exhaust/intake manifold gasket - tips?

Post by dpcd67 » Thu Jun 22, 2017 6:34 am

And you don't need to separate the exhaust and intake manifolds; if you do, those studs are the ones most likely to break, by far. I just drilled out and re-tapped four of them last week. I didn't break them. They get heat/rusted/locked in place and even the best penetrants don't work. Heat will work best if you really want to. Now, if the gasket is leaking, then you will have to.
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Re: Changing exhaust/intake manifold gasket - tips?

Post by Chuck Lutz » Thu Jun 22, 2017 7:46 am

Mike's suggestion to check if the two manifolds are dead flat is important....a machine shop can mill down them as a unit to insure they mate with the gasket evenly to eliminate leaks. Be sure that the heat riser is working CORRECTLY when you have the assembly out on the bench before doing anything!
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Re: Changing exhaust/intake manifold gasket - tips?

Post by Daegan » Thu Jun 22, 2017 2:23 pm

Thanks guys.

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Re: Changing exhaust/intake manifold gasket - tips?

Post by JIMN » Thu Jun 22, 2017 5:46 pm

I have taken a large flat file to surfaces like exhaust manifolds and headers and worked them flat while in a vise to ensure a good seal. Taking the assembly off and checking/correcting flatness is worth the effort. And of course you need to keep them bolted together to do it.
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