E320Star

I have e320 yr 2000, with 56,000 miles. Last month, both CATS have been replaced thinking this issue is related to the CATS. Well it appears it is not. The issue is after starting the car in the morning, and after the first idle is done "1-2 minutes after startup", the knocking sound begins and it lasts for about 5 minutes and then goes away for the rest of the day. It appears to be coming from under the car somewhere between the 2 CATS, what could this be? Pleeeease help.

E320Star

Please help

E320Star

Please, any idea's !!

kevins e55

resignators? and are you sure its coming from under the car and not the engine bay?

MG

You ran over your wife in the driveway. Back up slowly and call the EMS

cragigotgame

I had a problem when one the mounts for the exhaust broke off and needed to be welded back on. It would rattle at Idle, but if yours is more of a knock??? I dont know what part of the exhaust would really make a knocking sound.

E320Star

What are all of the scenarios? Where is the resignator? and what would be the cause if the sound coming from the engine bay?

Thank you

cragigotgame

I seriously doubt that the resonators are causing any problem. Sometimes your car will knock if you get some bad gas.

E320Star

But I always used 91 octane Premium unleaded from QTRIP gas stations. if it is gas related, the car will not run very well, but it does run great. Only the morning knocks that bothers me.

cragigotgame

Where did you have it checked? Aristocrat??

E320Star

Aristocrat. Yep.

C-2

I too had this problem.

In my case, the sound was rattling and it only happened while in gear, at idle, like at a stoplight or drive thru window. Not at highway speed, and not at idle while in park.

It was a broken weld on an exhaust bracket used to separate the pipes. the reason it rattled while in gear makes sense; the pipes share a bracket on the tranny and while in gear, there is engine/tranny movement. While in park, there is little or no movement, thus no load, and only little movement.

The break was barely noticeable and I only found it after wedging the pipes apart. If you look at it with no stress or pressure on the pipes ~ the weld looks good.

Figure out when you are getting your noise. In gear but at idle, or in park at idle. My sound disappeared at highway speeds and tracing a sound in the exhaust system can be misleading since noise travels up and down the pipes. Literally took me several hours to find the broken weld.

My neighbor put a quick weld on (it's carbon steel and can be welded) and has been fine ever since.

mike430sport

I had a problem with my cats also. I replaced them both and noise went away. I started to hear a rattling sound coming from under neath the car a month later. What I found is that there is a metal ring causing the sound, it goes in between the flanges. It is the flange that connects the Cat to the resonators. Check it out. That was my problem and had it fixed

cragigotgame

Yea it sound like its probably somthing vibrating underneath. I would take to an independent german car shop. There are a few around. Maybe even star motors. But I would avoid arisocrat.

Air Marshall Eldritch

I have this same thing now. Need to get under there to find out exactly where. Mine is a jingle/rattle mix at idle.

E320Star

wHAT IS IT I NEED to look for when I look at it. A warn out ring or rubber arounf th ring? what is it exactly. Do I need to replace thr ring regardless ?
Do you have a picture of what to look at at?

Thank you

Thrillhouse

get a rubber mallet get under there and hit the exhaust it wont hurt anythng, listen for the sound, if no sound drive the car and then do the same but be careful cuz it will be hot, if still no sound then its not the exhaust, sometimes the catalyst that came apart in your OLD cats could have been blown into the muffler or resonator, also check trans mount