Talk to me about replacing the pass exhaust manifold

tedlovesjeeps71 · Post by **tedlovesjeeps71** » Thu Mar 02, 2017 5:13 pm

So I need to replace the exhaust manifold on the wife's 91 waggy. My effort to make a broken stud repair failed and it's not sealing. Since this is the side with the heater box all in the way... is it possible to pull and replace the manifold with the box in the way? This job will be bad enough as it is because I noticed the front bolt is broken in the head. Hopefully none of the others are and come out without a fuss.
So any tips or advice will be greatly appreciated.

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letank · Post by **letank** » Thu Mar 02, 2017 6:52 pm

Aaaaack, I replaced mine, but soaked every bolts with PB blaster, or knock'er loose sprays.... in fact I drilled some holes in the inner fender so I could use an extension and a large breaker bar, I used neolithic impact driver -the one with the hammer- and even torched the bolts. DO not forget the heater valve bolt and remove the valve, have a shop plug the holes with a touch of weld.

After a few months -yes, month- every bolts loosen up...

As usual a little tightening before loosening to break up the rust

It has been said that running the engine before loosening the bolt is the key to a succesful exhaust manifold removal, but i did not go that way

Easy out do not work, for that broken bolt, you will have to center your drill bit dead center, and use large drill bits... it worked on the wrangler, we only mangled 1/8th of the threads

Cheapthrills · Post by **Cheapthrills** » Thu Mar 02, 2017 8:52 pm

Pull the heater box

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tedlovesjeeps71 · Post by **tedlovesjeeps71** » Thu Mar 02, 2017 10:13 pm

Cheapthrills wrote:Pull the heater box

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I don't suppose it comes out from the motor side without getting involved with the under dash stuff??

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Cheapthrills · Post by **Cheapthrills** » Thu Mar 02, 2017 10:15 pm

Under carpet there are a few bolts it's really not too bad. You may have pull the ac unit to make it easier tho so pull the bolts from engin Bay then pull carpet back and you will see 3-4 bolts you may be able to do it with out pulling ac

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tedlovesjeeps71 · Post by **tedlovesjeeps71** » Thu Mar 02, 2017 10:32 pm

Cheapthrills wrote:Under carpet there are a few bolts it's really not too bad. You may have pull the ac unit to make it easier tho so pull the bolts from engin Bay then pull carpet back and you will see 3-4 bolts you may be able to do it with out pulling ac

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That would be nice since if I don't I'm guaranteed to smash the plastic box. I should probably pick up a new heater core while I'm in it. I just pray the manifold comes off without snapping bolts. Be nice to get the AIR system removed and put in a box.

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tedlovesjeeps71 · Post by **tedlovesjeeps71** » Thu Mar 02, 2017 10:34 pm

So here's another question. The manifolds have a doughnut shape cast into them. Driver side on the manifold, passenger is cast in the heat riser. Since there isn't a way to add a doughnut, I don't, right?? Just the flat gasket for the heat riser to pass manifold.

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Cheapthrills · Post by **Cheapthrills** » Thu Mar 02, 2017 11:27 pm

Doughnut?

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tedlovesjeeps71 · Post by **tedlovesjeeps71** » Thu Mar 02, 2017 11:55 pm

Cheapthrills wrote:Doughnut?

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Doughnut gasket.

Like this:

Cheapthrills · Post by **Cheapthrills** » Fri Mar 03, 2017 12:02 am

I think I know what your talking about.... drivers idea is cast in like you said (aka collector) so no gasket needed. Passenger side has a piece with butterfly valve that opens with heat.... you need that but can modify to get rid of the butterfly valve because it can and will fail if it's not broken all ready, you would need to fill holes on the sides with a welder or maybe even jb weld .There is a metallic gasket for that but I'm sure you could make a gasket with a high temperature material I'm sure. Then the y pipe should fit direct from there.

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tedlovesjeeps71 · Post by **tedlovesjeeps71** » Fri Mar 03, 2017 12:13 am

Cheapthrills wrote:I think I know what your talking about.... drivers idea is cast in like you said (aka collector) so no gasket needed. Passenger side has a piece with butterfly valve that opens with heat.... you need that but can modify to get rid of the butterfly valve because it can and will fail if it's not broken all ready, you would need to fill holes on the sides with a welder or maybe even jb weld .There is a metallic gasket for that but I'm sure you could make a gasket with a high temperature material I'm sure. Then the y pipe should fit direct from there.

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Yup, that's basically what I did. Just wasn't sure why I thought I needed the doughnuts.
As for the butterfly, mine was loose on the cross shaft so basically worthless. I simply cut it off but left the crossshaft in place since it fills the holes. I may cut it out and weld the holes but I'm not decided if I need to. The shaft is only about a 1/4" (or less) in diameter and has nothing to fail now that the butterfly plate is gone.

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Cheapthrills · Post by **Cheapthrills** » Fri Mar 03, 2017 12:14 am

That'll work

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tgreese · Post by **tgreese** » Fri Mar 03, 2017 7:10 am

At the Jeep dealer, the mechanics had a procedure for exhaust manifold replacement. The dealership was next to an uncrowded freeway in California, and the mechanic would drive the Jeep fast on the freeway for maybe 6 or 8 minutes, so the manifolds were rocket hot. Then he'd pull in to the bay and remove the manifolds. This made the bolts come out without breaking. There are obvious hazards to this approach ...

mgbreis · Post by **mgbreis** » Fri Mar 03, 2017 7:34 am

Maybe some huge differences between '78 and '91, but I took my passenger side manifold out the bottom. However, I had the y-pipe off also, so that's probably a road block if it's in place.

ferrum · Post by **ferrum** » Fri Mar 03, 2017 11:51 am

When I took out my heater box, I ended up snapping off studs in the passenger side floor due to them being rusted from the water on the carpet over the years. You may have similar issue but it was relatively easy to repair. Studs in the engine bay had no problem as being caked with oil. Be very careful with heater resistor connector to not break it.

Cheapthrills · Post by **Cheapthrills** » Fri Mar 03, 2017 1:12 pm

Hey Ted I tried to call to see how your exaust project is going.
these guys are also correct. These are possibilities. Get your self a can bg enforce too or pb blaster and soak If you need to. If you do break the studs I have a heater box I can hook you up with. Or you may be able to remove broken studs and use some other bolts

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tedlovesjeeps71 · Post by **tedlovesjeeps71** » Fri Mar 03, 2017 2:10 pm

Cheapthrills wrote:Hey Ted I tried to call to see how your exaust project is going.
these guys are also correct. These are possibilities. Get your self a can bg enforce too or pb blaster and soak If you need to. If you do break the studs I have a heater box I can hook you up with. Or you may be able to remove broken studs and use some other bolts

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Hey, sorry. Didn't hear the phone. I'll shoot ya a text.

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Nikkormat · Post by **Nikkormat** » Fri Mar 03, 2017 3:49 pm

Knock on wood, I've had 100% success tightening before loosening. No special PB blaster or anything. You can get the manifold off with the heater box there.

Cheapthrills · Post by **Cheapthrills** » Fri Mar 03, 2017 8:57 pm

Think he said stud is broken

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tedlovesjeeps71 · Post by **tedlovesjeeps71** » Fri Mar 03, 2017 9:11 pm

First off, thank you to everyone who helped with advice!!! Just got home and the day ends with mixed results.
I WAS able to get the manifold off without me breaking any bolts. The air injection tubes didn't fare so well but at least they are gone!
Nikkormat was correct in that I didn't need to remove the heater box to get it out. I did pull the exhaust (again!) as well as the starter. The battery came out and I draped the charcoal canister over the motor. It was a bit nerve wracking but all the bolts I touched came out without much fuss.
But the story isn't all happiness and success. As I mentioned earlier, some PO had snapped the very front manifold bolt off. When I got the manifold out of the way I saw, unfortunately, that it snapped below the surface level. I had zero luck so far getting it out and at this point I can only drill it all out and hope to get some threads made or a helicoil installed. I sure don't want to pull the head!
So tomorrow I'll get up early, hopefully pick up my new heater core (had to order it) and if I'm lucky I can make good progress. I probably don't need to pull the heater box but I think it's time to replace the core now before it leaks. Plus it will give me much better access to clean out the leaves I wasn't able to reach before.
Thanks again everyone and I'll post up more progress tomorrow!

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