Flange Joint Between Rear Cat and Intermediate Pipe: Sagging?

Stats: 2003, 2.7L, 4WD, AT

I've had the "zombie" exhaust repair going on now for about 14 months. I thought I was finally getting close to having it "done" when another problem popped up.

Over that time replaced the rear cat, the intermediate pipe (between rear cat and muffler) the muffler and tail pipe and repaired the rear cat hanger brackets. The exhaust manifold and forward cat I have NOT touched, but they seem to be in fairly good condition.

This has all been done onesy-twosy over the past year plus. The intermediate pipe was the first piece to fail, so it was the first replaced. Unfortunately it was subsequently beat up by the system failing around it: the flange between the int. pip and the rear cat got hammered (I think) when a rear cat hanger bracket broke. Now the ears of the int. pipe flange (which WAS brand new a few months ago) are bent forward.

The last time I did a repair (replaced the rear cat) I thought I had messed up the connection between the forward and rear cats and THAT threw everything off. I have since completely removed the rear cat AGAIN and re-fitted it. I got the connection between the forward and rear cats to be what seemed totally spot on and snugged them up. That way I knew all I had to do was fit the int. pipe into the backside of the rear cat and things should have been good to go.

(Note I have repaired both hanger brackets on the rear cat so it IS supported properly.)

There are three hangers on the muffler/tailpipe assembly and all are tip top. The int. pipe has NO hangers.

I placed blocks under the rear cat and int. pipe to make sure everything was perfectly in-line before assembling and tightening that last flanged connection.

I tightened it until the flange ears touched. Unfortunately the int. pipe flange ears are bent forward slightly (but not horribly). I THOUGHT I had a good connection, but once it was all back together I tapped the blocks out from under both the rear cat and int. pipe and the flanged connection dropped and the joint went wonky:


3/4 of the joint looks good but there's a huge gap at the base of the join you can even see the gasket through.

If every hanger and every forward connection is good, why is it sagging?

Could it be that the damage to the int. pipe flange ears is what causing this? I meant to take a torch to the int. pipe flange ears and beat them back (rearward) into the original shape (more or less) the last time I was working on this... But this is my only vehicle and by the end of the day there was not enough time to do it and still have a vehicle the following day.

Should I pull it apart again and try to bend those flange ears back? Or should I bite the bullet and buy a new pipe?

I can get one for about $40. But if fixing the flange ears is all it will take, then why not do that and save a few bucks?

But could there be something else that's a problem? I'd hate to buy new stuff, tear things apart, put them back together, and only then find out that something else is a problem. I've had this system apart so many times I'm getting sick of it. I'd like to do one last job and know that will actually fix the system. Until it breaks again

But all the hangers and other connections seem fine... so what else could it be?

Any suggestions on the matter are greatly appreciated!

 

One does what one has to at times.

I learned long ago that mixing and matching exhaust parts from different manufactures is very frustrating .

Because nothing fits .

If your flange is bent get a new flange and weld it on .

With the exhaust installed even heated cherry red to much movement in the pipe to get it straight.

Not able to weld a new pipe made by the same manufacture

Form a gasket #2 and 2 gaskets might work to seal your exhaust

Best of luck!!

 

You are supposed to have a gasket between the flanges. In your case use 2.

They are about $3 each at AutoZone.

In addition, you have an exhaust leak and you will eventually get a check engine light. PO420 is the code. Catalyst inefficiency.

 

Try bending the ears first. If that doesn't work, hey - it's already not working anyway!

Happy Motoring, Mark

 

Thank you all!!

I've had the 0420 code for since a couple months after I bought the pickup... That would be almost two years ago. I've just been ignoring it until I get the exhaust system into some semblance of "normal." I did reset it after replacing the rear cat and even with two exhaust leaks (one now fixed) it has not come back on in 300 miles. But I'm not expecting it to stay off until I get this done right. Even then I know it still might be one of the O2 sensors (except if it was I would have expected it to return sooner rather than later). Last time I checked the O2 sensors I got inconclusive results, but my multimeter was crapping out. I have since replaced it with a Fluke so I can repeat O2 sensor tests (after the exhaust is fixed) with more confidence. Ah the joys!

I had never thought of using two gaskets, I'll definitely buy two as I've gone through a half dozen in the past year anyway.

I think I can get the intermediate pipe for for under $40 with shipping from RockAuto. They've consistently beaten the prices of the regional parts stores around here.

I guess I'll let the idea marinate... do I want to pull it apart potentially twice and thus draw the repair process out in an attempt to make the existing int. pipe work? Or do I spend the money on a new int. pipe in the hope that THIS time I will get things working 100% (more or less) without the need to pull things apart twice. I will meditate on this

I'll update the thread with how things go. Thank you so much, everyone!

 

I've had lots of problems with aftermarket exhaust pipes AND gaskets on Asian vehicles. Often the aftermarket substitutes a flat gasket for the original ring gasket - which will only work if the flanges are perfectly straight. Sometimes the only cure is getting the correct OE gasket at the dealer.
I don't think you'll have much luck until you get those ears straight, either by bending them, or replacing the pipe.

Happy Motoring, Mark