Hello all! Suddenly on the freeway, my 308 got much louder and hasn't stopped since. Rolled down the window and it sounded like the exhaust got louder. No codes, no vibrations, etc.

Any pointers to where common exhaust failure occurs? Sounds like it may be coming from the front of the car - but I haven't been on a lift to check everything.

 

Please update your info. It says your 01’ XJ8 is sold. What year is your XJ8 or R? There’s a reason for it.

 

Fixed! Currently driving a 2003 XJ8!

 

I know it’s not a flex pipe issue since that year didn’t come with one from the factory. All the AJ26/S (98’ & 99’) cars did and they were located at the front of the transmission. Anyways, enough rambling on... What you could do is start the engine and open the hood. Do you hear any ticking noise inside the engine bay? On the drivers side of the throttle body, you can manually blip the throttle a few times and listen if there’s any ticking noise in the engine bay. If you can hear ticking close by, it’s possible the gasket between the exhaust manifold and catalytic converter on either side of the engine may have failed. Do you know if the transmission has been out of that car or if an 02 sensor was replaced? As a secondary thought, maybe they use salt on the roads where you’re at (or wherever the car was at previously) and the exhaust is crusty??

 

Checked out more today, the left side exhaust system had a much stronger vibration compared to the right. It was also noticeably much louder. No ticking sounds noted, no O2 sensors were replaced. It did notice water leaking from one of the connection points in the photo below.

 

In the top photo, it’s possible that the 15mm nut just needs tightened. Tighten it when the engine is cold.

 

Just put the car up on ramps or jack stands, start it and crawl under it. You can follow the noise.

 

That exhaust connector from the CAT to intermediate pipe seems to always have a bit of a leak....at least on all the XJ8s I have owned. Will only get so tight and after that, it will break off with a bit more muscle. Once the clamp bottoms out against the thick metal stop it's as tight as it gets. You might spray some blaster or other penetrating oil on it before trying to tighten it though.
Best to you fellow Jag wrencher!