1999 E300 - deep knock above idle

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1999 E300 - deep knock above idle

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1999 E300 - deep knock above idle - 1/11/2008 11:00:38 PM

Lemosx4

Posts: 2
Joined: 1/11/2008
Status: offline

I'm a first time poster. I haven't had a chance to review all of the postings in this forum, so if this issue has already been addressed, I apologize.

My 1999 E300 has been a very smooth, quiet, powerful turbodiesel since I purchased it about 15k miles ago. It now has 123k, and has always been very well maintained.

However, today it began to make this horrible knock at any RPM above idle. It now idles a little rough, but not terrible. Above idle, it sounds like a rod knock, but I believe it's unlikely to actually be a rod. I am new to diesels, but am pretty mechanical. I don't mind working on it, but I'm reluctant to just start tearing it apart and replacing stuff. Any ideas what might be causing this knock and rough idle? Both occured today.

Any assistance is greatly appreciated.

Thanks,
Ed

Post #: 1

RE: 1999 E300 - deep knock above idle - 1/12/2008 6:24:18 AM

pimpernell

Posts: 26
Joined: 5/16/2007
Status: offline

96 E300d here:

Just offering some suggestions...first, I would take a look at the oil dipstick to make sure that the oil is at the proper level. From what you describe, it sounds to me like one of you injectors is clogged, and that particular cylender is not firing. The fact that it idles rough, and "knocks" at higher rpms would suggest that this might be the case. These engines have a tough lower end, and usually if a rod bearing is on the way out, it will do so gradually. The "knock" would have a tendency to increase in sound level gradually over time. From what you describe, this has just suddenly appeared and that would lead me to believe that an injuctor may be fouled. I am including a link to another web site where you can post and get a lot more info.........Good luck

http://www.mercedesshop.com/shopforum/index.php

(in reply to Lemosx4)

Post #: 2

RE: 1999 E300 - deep knock above idle - 1/12/2008 8:41:39 AM

Lemosx4

Posts: 2
Joined: 1/11/2008
Status: offline

Thanks much for the input. I believe the changing of the injectors is something I should be able to handle. Now, assuming it's an injector clogged or partially, or failed - is there diesel purge or some other injector cleaner that I can use to clear it out, or is it just too late now?

Also, how long do these injectors typically last? I wouldn't think 123k miles would kill an injector, but maybe it does.

Could anyone provide a quick step by step on changing the injectors on this car?

Thanks, Ed

(in reply to pimpernell)

Post #: 3

RE: 1999 E300 - deep knock above idle - 1/13/2008 10:30:50 AM

pimpernell

Posts: 26
Joined: 5/16/2007
Status: offline

check out this link, the problem is almost identical to yours, and they give some ways of checking it out. Good luck

http://www.mercedesshop.com/shopforum/showthread.php?t=202574&highlight=bad+injector

(in reply to Lemosx4)

Post #: 4