Hi there,

I have a 1999 4.0 XJ. I previously replaced the rear section of the exhaust from the cat back. The thing ran sweetly after that but recently a horrible vibration/ resonating noise has started in the section just after the cat. The new section was a good quality pattern part so presumably this is ok. I was wondering if the Cat is on it's way out causing the noise further down the pipe. The system is gas tight and not leaking anywhere and there are ni error messages on the dash.

Has anyone any thoughts or experience of a cat giving up, that could give me some idea what is wrong?

Any help would be much appreciated.

 

drive about 10 to 20 miles kinda fast or WOT for a while, then park the jeep and touch the cat if it's working right it should be warm or hot

 

Hi, it is getting hot, but only as hot as the rest of the system. Is there any other way of checking it? It looks as though its the factory fit unit and the car has about 78k on it. What's the life expectancy of these things?

 

Did you check to make sure that the system is not rubbing or touching any thing else under the vehicle. When the Cat fails it does not cause the exhaust system to resonate or vibrate, it will either Rattle, Perform Poorly during an Emission test, or plug up and cause a poor running condition.

 

Hi, I have been over the whole system and it is not rubbing or touching anywhere. The car is running perfectly and has just been through an MOT (UK test) which confirmed the emissions were ok.

From what you describe, it sounds then as though the cat is ok and a baffle may have come loose in the new rear silencer, as this is where the noise is loudest. Would that make sense?

 

I'm 99% sure the cat works if it gets hot and you pass smog

 

Mark, I believe you hit the little bugger on the head, could be a broken baffle in the rear silencer

 

Thanks Guys! I will contact the exhaust supplier and see if he will change it. There must be some form of warrantee in these things.

 

OF course after 10-20 miles running at high speed it will be hot even if it's not working right.

 

Mark, what year is your Cherokee?

 

1999

 

DOH! This is why I should wait until after coffee to peruse the interwebs.

 

Mmm cat toast....

 

Well, did you happen to hear meowing coming from the BBQ grill?

 

Well, did you happen to hear meowing coming from the BBQ grill?