Replacing exhaust manifold on Detroit


** Commie Express **
My exhaust manifold has a crack in it for the second time in 6 years. I hear it's normal. The first time I had a shop replace it and watched. It looked very easy.

I have a new one waiting for me at home. Any advise? I park my truck at my mechanics shop so if I get in trouble he can save me.

The bolts are all new from the last change out and never seize was used on the bolts. It looks like a straight forward job.

Looking for words of encouragement.

Racer X 69

What engine?

If the bolts are in good shape you might get away with reusing them, but the heat is hard on the steel. The chance that some may break is greater when they are re-used. I would use new bolts, same for the turbo studs and nuts. And new gaskets too, of course.

And always, use the Never Seize in the threads, bolts and studs.


Hobbie Trucker
Spray them down with PB Blaster tonight or atleast the night before you plan on taking it apart. When I do exhaust manifolds I'll do that. I also do them right after I come in off the road while everything is hot and still spray them with PB blaster.

Breaking one off sucks!


In Gord we trust!
Diesel engines are like bananas, not any good until they turn yellow. Lol

I posted that pic because Les loves drilling out broken studs. Just found one broken on my dads truck. Hope it doesn't happen to skateboard!
Diesel engines are like bananas , Get the green ones they last longer.


Well-Known Member
Getting rid of the stock manifold and getting a ported and ceramic coated one would do wonders for preventing the cracking and keeping exhaust temps lower. I put one on a DDEC IV, replaced the wastegated turbo with a larger non wastegated Borg Warner 171702 turbo with a turbo blanket, and put Walker Megaflow high flow mufflers on the stacks. Even under the hardest pulls, the EGT's never get above 900F, and most times under throttle, stay closer to 750F.

Detroit.... making the world greener, one engine at a time!


** Commie Express **
Well, I lucked out. My mechanics shop computer got that virus that redirects you to another site and shows up disk errors. He has antivirus but he let his nephew screw it up. So, tomorrow I rebuild his system and he puts on the new manifold.

My engine runs fine but at an idle it sounds like a bunch of marbles rattling around. Sort of like a 1970's diesel Rabbit did. Just bugs me.