Exhaust Manifold Leak

whydahdvr · Post by **whydahdvr** » Sun Jun 09, 2013 4:16 pm

So in working through some issues on my jeep with Rick Lee we discovered that my exhaust manifold is leaking from the gasket. I'm wondering if I can just replace the gasket or if anything else needs to be done.
Thanks.
-JJB

Xamon · Post by **Xamon** » Sun Jun 09, 2013 4:48 pm

About all I could suggest is checking the mating surfaces to make sure they are true, if they are not you might never get it sealed.

Post by **wesk** » Sun Jun 09, 2013 11:27 pm

Both the block surface and the intake and exhaust mating surfaces can be machined to make them true again. When you get them off wire wheel the surfaces clean and check them with a straight edge. If any polishing of the manifold face is needed be sure to shave both the intake and exhaust equally.

whydahdvr · Post by **whydahdvr** » Mon Jun 10, 2013 6:42 am

Wes, you're saying I'll need to pull the engine out to get that face smoothed as well as the manifold? What do you recommend doing to check to see if it does need to be planed?
What I saw was greyish vapor looking like it was coming from between the engine and the manifold. I'll check to see if it's something else causing that vapor but is there anything else I should check?
Thanks.

Post by **wesk** » Mon Jun 10, 2013 8:51 am

When exhaust leaks start they are very corrosive. They will first burn away the gasket then they start to erode metal from both surfaces. The longer you ignore the leak the more costly the repair will be. As I said above you first thoroughly clean the surfaces then you use a straight edge across the surfaces to detect gaps where material has eroded away.

I don't look for vapors with exhaust leaks. I listen for the nasty noise and feel close to the parting surfaces for the actual flow of exhaust gas with my hand while racing the engine.

Most folks are too cheap or too lazy to properly correct the block surface erosion which requires removing the block and having the surface machined. Instead they do ridiculous little tricks like use red silicon to fill the void and a new gasket. That is the dummest band aid I have ever seen. Putting anything made from silicon rubber in front of a fire burning well over 800 degrees! But they do these dumb arse tricks until they finally sell the problem to someone else. Whom they tell "Oh, not to worry mate, just needs a new $10 gasket!"

whydahdvr · Post by **whydahdvr** » Mon Jun 10, 2013 9:24 am

Ha!

Gotcha! Thanks Wes. Not sure how long this has been the situation but I'll take a look and see how it is.
Thanks for info.

whydahdvr · Post by **whydahdvr** » Wed Jun 12, 2013 10:05 am

I pulled off the exhaust manifold and checked both the block and the exhaust manifold with a straight edge. The block-side face is flat, just needs to be cleaned up from the gasket. The manifold side has a slight gap across the whole surface on the center section. It's like the two side flanges are slightly raised up from the center flange.
I've ordered new gaskets and will take the exhaust manifold assembly to get evened up and then go from there.
Thanks.

Post by **wesk** » Wed Jun 12, 2013 10:55 am

L134 or F134? If L134 take the intake and exhaust as a complete assembly for resurfacing.

whydahdvr · Post by **whydahdvr** » Wed Jun 12, 2013 12:00 pm

1952 M38 so L134.
Yeah, logically to me it looked to make sense to take the whole assembly since that combined face is mating with the block.
Thanks.

And so now the exhaust manifold assembly is off at Hillside Machine in Malden, MA to get evened up. Parts on the way and we'll see how it all goes back together when the time comes.

whydahdvr · Post by **whydahdvr** » Mon Jun 17, 2013 11:35 am

Latest update:
The first machine shop I was referred to got rid of his sander. The one that place recommended me to couldn't fit the exhaust manifold assembly into either of their machines so they couldn't do the work. They referred me to another place, Malden Machine in Malden, MA but from their website it looks like they mostly do hot rods and racing engines.
So my question is, if I can't find someone soon to even up the exhaust manifold flanges, will I be able to get away - for a while - with doubling up gaskets? Then during the Winter I could track down a place to do the work.
Thanks.

Xamon · Post by **Xamon** » Mon Jun 17, 2013 11:54 am

wouldn't recommend it, if you put in more material then you have to torque more to get a good seal which in turn pulls the studs and warps the engine block.

whydahdvr · Post by **whydahdvr** » Mon Jun 17, 2013 11:57 am

Oh. That makes sense. What about when the flanges are evened up? There's going to be a little less metal. Would you run into an issue that way too? Maybe not....

Post by **wesk** » Mon Jun 17, 2013 11:59 am

looks like they mostly do hot rods and racing engines.

Makes no difference what type engines they are into. If they have the time, and the equipment they can do your resurfacing.

jimm · Post by **jimm** » Tue Jun 18, 2013 4:23 pm

wesk wrote:Both the block surface and the intake and exhaust mating surfaces can be machined to make them true again. When you get them off wire wheel the surfaces clean and check them with a straight edge. If any polishing of the manifold face is needed be sure to shave both the intake and exhaust equally.

Wes - in your opinion, how much of a mismatch between surfaces is too much? Say you put a straightedge across them, which will hit only the two high points, and you check the low spots with feeler gauges. A few thousandths? 10 thou?

Post by **wesk** » Tue Jun 18, 2013 5:30 pm

0.010" is the general rule of thumb.