I took my 1990 XJ to get inspected today and it failed. It’s never failed before. They told me that there was a hole in the exhaust where it meets the manifold, and a hole in the firewall. I was driving back from the shop when it sounded like something dropped down or popped, and my engine started making sounds like a dirt bike or lawn mower idling, and I got hit with a terrible smell. I pulled over to check it out and couldn’t see anything out of place. I drove back to my school, where I live, and parked it in the lot. Not sure if this is something I can fix myself or not

 

It sounds like something had a hole that got larger. Are you able to crawl underneath it and maybe snag some pictures? That would help a lot. As far as repairing it yourself, are you mechanically inclined at all / do you own tools, jack & stands?

 

I think it may be the exhaust flange gasket, or at least that’s the advice I’ve been given

 

ill crawl under tomorrow, it’s pouring rain today. And I can usually do simple jobs myself or with the help of my brother. I have jack stands and such available at home

 

This is the gasket just behind the crossmember, and I think it’s clearly in need of a replacement

 

Hmmm.. the exhaust is rusty.. but most older exhaust pipes are. I'd check around the pipe where it comes off the engine (exhaust manifold) and see if you can see any cracking.

When that sucker is COLD, grab a hold of it and see if you can move it and see where 2 parts aren't moving "together" if you know what I mean...

 

Are these pieces supposed to be attached or should they come off?
its not so rusty up near the manifold. I just took off the bolts in the picture, which were a nightmare.

 

It looks like the pipes were cut and welded 2x, once behind the shiny pipe to the far left in the picture, and then once behind the flange. Interesting that they'd have a clamp there though...

Since you have it off, replace the gasket.. but you really need to look at the manifold itself. The shop indicated that there was a crack in the manifold (which is incredibly common for the Jeep 4.0L), so you need to at least strongly consider that they're correct and check it. Typically the pipes crack where they join together (the Y sections). It may be hard to get a good look at it, but you need to be sure.
An exhaust manifold replacement isn't terribly difficult, but it's a fair amount of work. If you get the manifold off, it may be possible to just weld the crack (especially if you need a short term fix).

Certainly you can replace the gasket, put it back together and fire it up and see if the sound is better.

 

i am probably gonna replace the manifold completely because it’s old anyway but I figured it out. When I was driving, the #6 spark plug wasn’t tight enough and popped out. I was following the noise to the engine bay and felt the air shooting at my face. Engine runs normally again. But since I took apart the gasket I’m gonna replace it anyway

 

Quick question where this exhausts flange meets is on a solid bracket has anyone ever put a hanger here to allow a little more flex in the exhaust i feel like this is where my low idle vibration is coming from if i hold the muffler with gloves on it stops