95 850 T5 rattle noise coming from front of the motor.

[anmartin44]

I'm pretty sure an NA won't throw the cat code due to it not having an o2 sensor after the the cat. mine was completely blown out and i never got any codes.

[abscate]

Dont let the neighbors catch you doing this, but if you put a short piece of hose to your ear, you can isolate where sounds are coming from to the nearest 2.54 centimeters, give or take 3/8 of an inch. This can really help you diagnose which part you need to replace.

[jacobharding]

My dad showed me that trick one day. I thought he was nuts at first but it really does work. On the plus side If you plug it into the vacuum T it also will get a lot of the old wax out of your ear. Two birds, one stone.

[abscate]

LOLOLOL....dont forget to wax the car afterwards - its both green and frugal...well, more orange actually

[rmmagow]

I have an AWD turbo and a second 02 sensor but never had a cat code. I don't hear very well, but maybe I can get my wife to try the hose trick to isolate the noise. I had the car on ramps, idling and rattling away. I banged on the cat but the sound didn't seem to change much. I'm sort of hoping it is the tensioner as the is easy to change, cat, not so much.

[woodchopper]

I have this problem on a 98 V70 FWD. With a stethoscope in seemed to be the spring part of the serp belt tensioner. Took tensioner off and idler bearing seemed okay, so packed it with grease and put it back on car. Still noise. Does something happen in the spring part of the tensioner that lets it rattle at low rpm.

I sure wish I had taken the rattle more seriously, it turned out to be the idler on the timing belt and it cost me an engine. Lee's suggestion of taking the serpentine belt off would have solved it for me. Very expensive lapse in judgement.