Trying to diagnose an exhaust manifold leak on 89 YJ 4.2

Recker

Recker

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Oct 17, 2020
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vancouver
https://imgur.com/a/aK2ntpW

Trying to diagnose, just a backyard do it yourself'r. Tear down doesnt seem the worst. Also need to do valve cover gasket so i guess im really gonna have to get in here the next few weeks. Should I just get it to a mechanic and have him do it? I got a guy for $70 an hour who is reliable.

I was getting a hiss down by the brake pedal in the cab so figured brake booster but did all the brake booster checks in the chilton manual. When i removed the vac line to booster and seal it it runs decent when warm. Lots of vac to that line. Nutter bypass. Dont know compression numbers yet but i have a compression tester. I had a crack in the exhaust pipe where it mates to the manifold, welded that shut and its solid now, used high temp gasket seal putting the pipe back on where the flange mates to manifold.

When i put it back on vac line to booster the interior hiss went away... but in taking off the air filter housing i noticed the exhaust gas coming out from the block like as in the video and i cant source it any better to see if there is a crack.

Likely culprits for the fumes in above video? Avenues to pursue? Im a student and this is my daily, i dont have 8 hours at the moment to tear off, get the manifold to a shop to be checked, and then get it back on. Need new intake/exhaust gasket - looks like they share one?

Thanks
 
My guess is those fumes you see is just oil steaming off the hot cast iron exhaust header. Get some spray degreaser and clean off all that dirt and oil before changing the cover gasket. When it's dry and clean you'll see black carbon building up if the exhaust is actually leaking.
 
attack a small piece of toilet paper to a stick and hold it by the suspected leak. An exhaust leak will blow and flutter the toilet paper ! you'll have to get creative to block the fan breeze or just remove the belt during the test
 
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