Loose pre cat bolts

AndyG

AndyG

Because some other guys are perverts
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My 2003 4.0 pre cat bolts refuse to stay tight.

I have replaced the bolts , I have used prevailing torque nuts , lock washers , exhaust sealant at the connection and also high temperature thread lock.



The only way it will not have an exhaust leak is if they are just absolutely super tight.... And the second one backs off the slightest it begins to tick.

I'm wondering if the previous owner ran the jeep with the exhaust loose enough that they eventually deformed the flared connection... And when it seals it just seals marginally and is basically bottoming out.

I'm ready to throw another y pipe on the Tj

It has 51,000 miles.

Help me get the confidence to do this or tell me what I'm doing wrong.

I am at my wit's end.

AndyG
 
High temp thread lock like Loctite 272 is only good to about 450. I don't think that'll work for exhaust manifold temps. I've had good luck with lock-nuts and not lock washers. The type with the crimp at the top of the nut, I think they are some copper alloy. The split type also work, called top lock or something. Junkyard or Grainger? I've never had to buy them but they are common on exhaust manifolds, both on the block and flange.

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pagrey said:
High temp thread lock like Loctite 272 is only good to about 450. I don't think that'll work for exhaust manifold temps. I've had good luck with lock-nuts and not lock washers. The type with the crimp at the top of the nut, I think they are some copper alloy. The split type also work, called top lock or something. Junkyard or Grainger? I've never had to buy them but they are common on exhaust manifolds, both on the block and flange.

View attachment 161556
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Thanks
 
Have you tried loosening them and pushing the exhaust in a different direction before re-tightening? I know for a fact my exhaust will tighten down at different angles depending on how it’s positioned when I snug those bolts.
 
Rubicon John said:
Have you tried loosening them and pushing the exhaust in a different direction before re-tightening? I know for a fact my exhaust will tighten down at different angles depending on how it’s positioned when I snug those bolts.
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No...and I have questioned if I have them tightened evenly.

I have even doubled nuts and have an extra hanger up front .

Everyone insists it is a metal to metal connection, but O'Reilly's shows a fel -pro donut gasket for them.
 
AndyG said:
No...and I have questioned if I have them tightened evenly.

I have even doubled nuts and have an extra hanger up front .

Everyone insists it is a metal to metal connection, but O'Reilly's shows a fel -pro donut gasket for them.
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Mine don’t have a gasket. If the exhaust end is flared around the manifold that should be good enough.
 
For what ever reason, my jeep runs better with a little leak.
Too much leak and it will throw strange shenanigans from time to time, with leak eliminated it became noticeably sluggish.

Double nut it, like Jamison suggested.


... on another note, my jeep did come with some aftermarket exhaust, that is noticeably loud, so maybe there is some voodoo going on there.
 
I did the double nut trick...no joy.

Again. ... I think it was wheeled so hard and ran so loose the connection is worn to the point that you just can't pull together beyond barely touching , or it's elongated ,etc.
 
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Mine slowly work themselves loose. Every so often it will throw an O2 code and I retighten them. Might put more thought into it when I replace the cats & pipe.
 
LONGJP2 said:
Mine slowly work themselves loose. Every so often it will throw an O2 code and I retighten them. Might put more thought into it when I replace the cats & pipe.
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We commonly re-tighten after a few heat cycles while the exhaust is still pretty toasty.
 
Mine used to always work loose too.

Recently I had the pipe off to install an o2 sensor. I added a vband right after the Y, and when I tightened the cat bolts back up I just yanked the y pipe (disconnected from the rest of the rear exhaust) in every direction while hitting them with an impact, half expecting them to break, but they held and have been good since.

I only mention the vband because I think I remember there being a joint in the exhaust somewhere you could disconnect for more movement while tightening, but I don't remember where. Mine's been hacked up probably 10 times now
 
mrblaine said:
We commonly re-tighten after a few heat cycles while the exhaust is still pretty toasty.
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Now that is good info... And what mine appeared to need today as well.

I was able to tighten up a couple of the bolts pretty good bit.. everything looks pretty even and I'm hearing a slight tick that goes away pretty quick I almost wonder if it's a lifter.
 
If you use a jamnut and then put just a small spot weld to hold them together they won't loosen up until you either grind or pop the weld. Had an exhaust manifold nut that would keep loosening until I did this.
 
I would have to agree with you leaning towards the Y-pipe being deformed. The flare up by the engine may be out of whack and its not helping the clamping abilities.
 
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I few years ago, I removed the y-pipe on my 2006 so I could remove the oil pan. Mine had no gaskets and the hardware was extremely tight and slightly rusted. Had to soak it in 50/50 acetone/trans fluid over night. I replaced the extruded U nuts and bolts with a MOPAR kit I found on eBay. I haven't put a wrench on them to see if they ever loosened, but I don't hear any leaks.
 
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I have been fighting a leak on my 2003 in the same spot. I tightened them to point of breaking one of the bolts so I decided to just replace them all and it's not any better.
 
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