Help with 4.2 Exhaust

Help with 4.2 Exhaust

Coach

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Location
Dallas, TX
Vehicle(s)
1986 CJ7 / 4.2 I-6 / Auto / Dana 30 / Dana 300 / AMC 20 / Hard Top
I'm trying to shore up some engine issues as I save up for an engine and trans swap, so here is my problem:

Where my exhaust and front pipe mate up, I seem to have lost a seal that was between the two parts and the front pipe is loose. Also, the strange piece that was welded onthe top of the front pipe just below the coupling and wrapped under the motor fell off and wasnt in use anymore. I say that since the PO had a bicycle handle bar plug electrical taped into the end on the opposite side from the exhaust. Now I have an open hole where it used to be welded on.

I need some tips on shoring this up and losing the exhaust smell in the cab now that I have my hard top on for the winter.

I think this is what I need, but would rather find it locally and not pay shipping:
http://www.jeep4x4center.com/product-information.asp?number=3216643

I can't get it to come up at autozone.
Thanks for any help.
 
Last edited:
Yeah, the exhaust donut

NAPA part #EXH 31404
$6.99

151230.jpg
 
I really thought they had quit using the donut gasket by 80 or 81. When you buy one go ahead and buy two. you may go through them faster than you think. I found that the best way to loosen the studs on the manifold is to heat the stud with a propane torch and melt a bit of paraffin wax into the threads. some one here told me about this and this was the first chance I have had to try it, it worked great. PB and WD didn't even touch it.
don't hesitate to replace the studs, those can be bought at Napa too but they come in a package of three.:cool:
 
And that strange peice under the coupling that fell off, Maybe the oxygen sensor?
 
I really thought they had quit using the donut gasket by 80 or 81.

My 85 doesnt use a gasket. Just two studs from the manifold tightened up and the pipe snugs right up to the manifold with its beveled end. No leaks. I just took the new exhaust of my parts Jeep and it was the same way.

As far as the hole in your exhaust if its a few inches down the pipe there is a tube that comes up from the catalytic converter that attaches there. I dont have a cat myself so I just hammered the tube flat.
 
Heres 2 pics that may help you out a bit. The first shows where the pipe comes in from the catalytic converter. I closed it up with a ball pean hammer. It would normally look like a small tube. Is this what fell off? The second is my old pipe. If yours is loose get it ssecured pretty quickly. The heat , vibration and wieght of the exhaust will cause the flanged end to crack like in the pic. I grabbed the pipe off my parts Jeep. A new one will run you around $65

exhaustpipe2.jpg

exhaustpipe.jpg
 
And as was said, you want to tighten this up as quickly as possible so you dont damage the flange from the movement of the exhaust. It will also cause you to have to replace the bolts as they will wear at the threads pretty quick.
 
Thanks for all the input, I have the piece ordered and will be ordering some replacement studs too, as soon as I can figure out the part number at napa. I will also be hammering that pipe closed to seal it off when I'm in there doing the work on the coupling.

Thanks
 
You dont need the part from Napa. That is for earlier year Cjs. :)

I'm pretty sure it had one in there when I bought it. It blew something out and then there is a pretty good gap in the coupling now. Could be the PO added it for some reason.

What is the best way to get at the studs to tighten them? Haven't crawled under to look yet, but I'm guessing the heads to the studs are on the bottom, since I don't see them from the top looking in.
 
I'm pretty sure it had one in there when I bought it. It blew something out and then there is a pretty good gap in the coupling now. Could be the PO added it for some reason.

What is the best way to get at the studs to tighten them? Haven't crawled under to look yet, but I'm guessing the heads to the studs are on the bottom, since I don't see them from the top looking in.

I use a socket driver with like...3 extensions on it I think :D
 
Mine were screwed up and replaced with bolts at one point. If you still have the studs there then theres a good chance the correct nuts are on them as well. They are the length of two standard nuts together. If their on there all you'll need is a standard 3/8 ratchet and 9/16 socket. The extra length of the nut enables you to use the standard socket and attack it from the top. If they arent there you'll need a universal and some extensions to grab the rear one from underneath.
What is the best way to get at the studs to tighten them? Haven't crawled under to look yet, but I'm guessing the heads to the studs are on the bottom, since I don't see them from the top looking in.
 
I really thought they had quit using the donut gasket by 80 or 81. When you buy one go ahead and buy two. you may go through them faster than you think. I found that the best way to loosen the studs on the manifold is to heat the stud with a propane torch and melt a bit of paraffin wax into the threads. some one here told me about this and this was the first chance I have had to try it, it worked great. PB and WD didn't even touch it.
don't hesitate to replace the studs, those can be bought at Napa too but they come in a package of three.:cool:
Machinists have been using that method for years with great results.
 
My 85 doesnt use a gasket. Just two studs from the manifold tightened up and the pipe snugs right up to the manifold with its beveled end. No leaks. I just took the new exhaust of my parts Jeep and it was the same way.

As far as the hole in your exhaust if its a few inches down the pipe there is a tube that comes up from the catalytic converter that attaches there. I dont have a cat myself so I just hammered the tube flat.
^^^^^mine too^^^^^
 
^^^^^mine too^^^^^

Alright, I'm starting to think this exhaust doesn't need the puck. I did find out it doesn't have the stock studs, so I will see if I can just snug it up. I'm thinking the PO had something in there that blew out.

I'm leaning towards keeping the engine and trans and doing a TBI now and holding off on the engine and trans swap for a while. So I need to get this done right, thanks for the help.
 
If they used a bolt/nut combo you may not be able to get it tight enough if they used a bolt with too big of a shoulder on it. You should be able to get it good and tight with the right hardware. If you go a little too long with the rearward one you wont be able to get a socket on it after it tightens so far. Did it have the 'longer" nuts like I mentioned before?
 
If they used a bolt/nut combo you may not be able to get it tight enough if they used a bolt with too big of a shoulder on it. You should be able to get it good and tight with the right hardware. If you go a little too long with the rearward one you wont be able to get a socket on it after it tightens so far. Did it have the 'longer" nuts like I mentioned before?

All I see are the bottoms of two bolts facing up. The threads are level with the lip on the header. When I reach up under thenfront pipe lip, I can feel the head of the bolt.

I'm going to try to get a socket on it today and see if either will budge. If they don't move, I will start using pb blaster and see if I can break them free. If not, I will have to find a way to try the wax technique mentioned earlier.

Thanks
 
Alright, this is what I'm dealing with right now. I'm trying to get it loose and see if I'm going to need the exhaust puck or not. I think it had one in there, since it is so loose right now and there isn't any movement in the nuts.

I'm guessing these aren't stock.

The stuff dripping off is PB Blaster to try to get some movement out of them.

Thanks for any help or input.

web.jpg
 

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