Clicking noise
 

I own a c280 1998 w/80k miles. when car is in park or just sitting idle, i will hear what seems to be a clicking noise coming from underneath. this is not always, just sometimes. Is this a tell tell sign of a bad catalytic converter?

Could you be a little more specific on the sound? What frequency/how often?

That clicking noise is probably your exhaust tubes hitting the idler arm or subframe. Check the tubing coming from 1-3 and see if there hitting the idler arm or the subframe. I got this problem with mine but it dosent bother me. When It gets warmer Im going to fix it. Mines hitting the idler arm.

more like a rattling sound. mainly when car is in idle. really no pattern, it's random. wish i could be more specific. mechanic said catalytic converter needs replacing just from hearing the sound, not even putting car on lift. I am skeptical about this diagnosis. $1000.00!!!

engine shock rattle?

if so..... a 30 cent rubber grommet takes care of it

revabob, could be as simpole as a loose honeycomb element inside the catalytic converter. Nothing that would necessarily require replacing the catalytic converter unless the noise is especially bothersome.

thanks for the reply. if it is that, can it be fixed without replacing converter or do I just have to live with the rattle? and how can one tell if it is what you are suggesting?

how can I tell if it is engine shock rattle? thanks for input

revabob, I guess by "engine shock" you mean the drive belt tensioner shock. Have someone rev the engine slightly while you look at the tensioner and listen for the rattle you've described. If that's the source simply replace the tensioner shock, or possibly just a worn grommet on the tensioner end.

I had loose honeycomb in my cat and discovered a good test: Get a rubber mallet and lay under the car (NOT RUNNING!) and thump the cat body with the mallet. If you hear the rattle there is your answer. You can buy an aftermarket cat here for a lot less than you were quoted, call Phil.

That seems very logical, thank you mpolli

well I narrowed it down even more, when not moving and car in drive or reverse with foot on the brake is when rattling occurs. If I put car in nuetral or park rattling stops.