Exhaust Flex Coupler Idea

[Blue Clearwater]

I'll start by saying that I haven't done a lot of work on exhaust systems beyond replacing mufflers. I am, however, a competent welder and steel fabricator, FWIW. So, if I'm missing something, let me know. Recently, the (I'm assuming) OE exhaust header on my TJ developed several cracks. I had installed a new muffler and when I did something must have gotten a little tweaked. We were out on some back roads shortly thereafter and the front driveshaft started rubbing on the exhaust pipe where it passes between the shaft and the oil pan. Nothing was loose, but I used a piece of wire to pull the exhaust away from the shaft just enough so it wouldn't rub. I'm guessing that, by so doing, I introduced just enough stress to the header to cause it to crack in several places next to the welds.

The whole thing got me to thinking though. I know these headers are known for cracking. Why not put a braided flex coupling in line in the pipe, either where the pipe passes between the driveshaft and oil pan or where it passes in front of the oil pan? I think it would require another hanger downstream of the flex coupling. Seems like this would help alleviate a lot of the stress on the header. I'd probably use V band flanges on either side of the flex coupler and the factory connection at the downpipe, although I did consider a V band coupler there as well. Thoughts? Maybe this is something that's already been done? I couldn't find anything on it.

 

[TJ4Jim]

I'll start by saying that I haven't done a lot of work on exhaust systems beyond replacing mufflers. I am, however, a competent welder and steel fabricator, FWIW. So, if I'm missing something, let me know. Recently, the (I'm assuming) OE exhaust header on my TJ developed several cracks. I had installed a new muffler and when I did something must have gotten a little tweaked. We were out on some back roads shortly thereafter and the front driveshaft started rubbing on the exhaust pipe where it passes between the shaft and the oil pan. Nothing was loose, but I used a piece of wire to pull the exhaust away from the shaft just enough so it wouldn't rub. I'm guessing that, by so doing, I introduced just enough stress to the header to cause it to crack in several places next to the welds.

The whole thing got me to thinking though. I know these headers are known for cracking. Why not put a braided flex coupling in line in the pipe, either where the pipe passes between the driveshaft and oil pan or where it passes in front of the oil pan? I think it would require another hanger downstream of the flex coupling. Seems like this would help alleviate a lot of the stress on the header. I'd probably use V band flanges on either side of the flex coupler and the factory connection at the downpipe, although I did consider a V band coupler there as well. Thoughts? Maybe this is something that's already been done? I couldn't find anything on it.

If you look at the 4.0 replacement manifolds they are available with built in flex to compensate for expansion. My son had that on his XJ and it held up without issues. Not on the down pipe, just between the front and rear pipes.

 

[Blue Clearwater]

If you look at the 4.0 replacement manifolds they are available with built in flex to compensate for expansion. My son had that on his XJ and it held up without issues. Not on the down pipe, just between the front and rear pipes.

I haven't seen one with a flex coupler where I described, just between cylinders 1-2 and 5-6, which is what my (again, I assume) is the factory header that cracked has. That's not where my cracks are though. But maybe I'm not looking at the right manifold/header? Do you have a link to the type you're referring to?

 

[KennethS]

My factory manifold cracked, and analyzing where the cracks were while lying under the Jeep and examining the exhaust system led to some observations. The system is anchored at the front by the manifold, and there are 2 hangers, one near the catalytic converter and one near the end of the tail pipe. The entire length of the exhaust system can move laterally on those pivot points - I often heard the pipe making a slight banging sound every time I took off from a stop. Looking at the way the pipe goes under the engine showed it puts lateral stress on the front anchor point (the manifold) with the mass of the catalytic converter enhancing that stress. It seemed that having an anchor from the exhaust pipe to the frame near where the pipe traverses under the oil pan would relieve the stress on the manifold. So I attached one of those generic exhaust hangers at that point, and it seemed to work. Unfortunately, the rubber on that hanger tore after a while, so something more durable would be needed for a long term fix.

 

[TJ4Jim]

I haven't seen one with a flex coupler where I described, just between cylinders 1-2 and 5-6, which is what my (again, I assume) is the factory header that cracked has. That's not where my cracks are though. But maybe I'm not looking at the right manifold/header? Do you have a link to the type you're referring to?

Does your current manifold have any flexes. The one I was referring to is what you described. They added the flexes there to remove the stresses from the 4 center tubes. Not a lot of cracking complaints about that type of manifold.

 

[Blue Clearwater]

My current manifold has flex tubes between cylinders 1 and 2 and between cylinders 5 and 6. This is the factory setup, if I understand correctly. The cracks that I have are past all of that, not where those factory flex locations are helping. What I'm proposing is a flex coupler past all of that, between the outlet of the header and the rest of the exhaust pipe, past the first O2 sensor.

 

[Blue Clearwater]

My factory manifold cracked, and analyzing where the cracks were while lying under the Jeep and examining the exhaust system led to some observations. The system is anchored at the front by the manifold, and there are 2 hangers, one near the catalytic converter and one near the end of the tail pipe. The entire length of the exhaust system can move laterally on those pivot points - I often heard the pipe making a slight banging sound every time I took off from a stop. Looking at the way the pipe goes under the engine showed it puts lateral stress on the front anchor point (the manifold) with the mass of the catalytic converter enhancing that stress. It seemed that having an anchor from the exhaust pipe to the frame near where the pipe traverses under the oil pan would relieve the stress on the manifold. So I attached one of those generic exhaust hangers at that point, and it seemed to work. Unfortunately, the rubber on that hanger tore after a while, so something more durable would be needed for a long term fix.

A hanger as you describe is essentially what I'm talking about, with the addition of a flex coupler somewhere between that hanger and the header to help relieve that stress further.