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Old 07-31-2009, 01:38 AM
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rattletaptaprattle. Bad injector?

Aside from the normal diesel growl there is a ramdom light rattle/tap at idle, also a very slight lope - lope is inaudible and almost indetectable by feel. if I boost the idle a little this tapping speeds up with it but remains inconsistent. At ~1300rpm it becomes perfectly smooth and has only the normal mild diesel growl and devoid of any strange sounds, just smooth sweet and eager sounding.

Im thinking if it were a rod, lifter or a cam bearing or something it would get louder as RPMs increase AND it would be more consistent, this tap Im attempting to describe does not sound with each stroke but only when it wishes and in varying intensity from moderate to very mild. Think marble in a bottle. The long screwdriver against the block and head to my ear netted nothing but the normal smooth clickclickclickclick fairly consistent from front to rear. If I had to try and isolate the sound its from the top half of the engine and maybe center or frontward but its hard to isolate.

Does this sound like an injector firing to soon or to much?

This engine has Hydraulic lifters, correct? (87 603 300SDL)

Hard part failure? most of my trouble shooting is with gasoline engines and Im fairly new to MB diesel. Any pointers or input welcome. Milage is unknown, vehicle history is subjective. This engine feels really good aside from this sound.

TIA for responses and pointers. I have to proceed carefuly as cost is starting to become an issue.

Thanks folks!!!

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Old 07-31-2009, 08:00 AM
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I have dealt with injectors that sound the same exact way, the marble in a bottle.
You could isolate the offending injector with a stethescope, and replace that one with a known good one or rebuild it. But if one is bad enough to be making noise, chances are the spray pattern isn't optimal on any of them.
Best bet is to pull them and have them rebuilt, reinstall with new crush washers.
Another way to find the culprit is to crack the injector lines one by one. If you get to one and it stops, you've found it. It would also eliminate valve noise or lifters as the source. But your engine is well known for having lifter noise, particularly at idle. Lots of info in the archives about that.
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Old 07-31-2009, 08:03 AM
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It sounds like an injector to me, I have a similar noise except (from your description) worse and through most of the RPM range. If you search "nailing" you'll get a lot of results...it kind of sounds like a hammer hitting solid metal every so often? Lifter tick would sound the same as on a gasser - ticktickticktick throughout the RPM (my car has this too, and so does the engine in my stealth). Sometimes changing the weight of the oil can have an affect on lifter tick, but overall that isn't something to worry about. The injector is probably clogged or worn out - you should try a diesel purge to get the crud out, see if it runs any smoother. The next step would probably be rebuilding the injector.
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Old 07-31-2009, 08:30 AM
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Quote:
Originally Posted by tbomachines View Post
It sounds like an injector to me, I have a similar noise except (from your description) worse and through most of the RPM range. If you search "nailing" you'll get a lot of results...it kind of sounds like a hammer hitting solid metal every so often? Lifter tick would sound the same as on a gasser - ticktickticktick throughout the RPM (my car has this too, and so does the engine in my stealth). Sometimes changing the weight of the oil can have an affect on lifter tick, but overall that isn't something to worry about. The injector is probably clogged or worn out - you should try a diesel purge to get the crud out, see if it runs any smoother. The next step would probably be rebuilding the injector.
I don't think your car has hydraulic lifters, that started with the OM 603 I believe. But the original posters car does.

A diesel purge won't hurt, but I've never had long term luck with it. Makes the engine run smoother while the purge is going (probably due to the different combustion point than diesel) but any nailing always came back afterward. Dirty injectors are stubborn. Pulling the injectors and bringing them to a shop or sending them out for a rebuild is easy and relatively (to other repairs) cheap. One of the best things you can do for ANY old diesel.
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Old 07-31-2009, 08:45 AM
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Quote:
Originally Posted by UriahT View Post
I don't think your car has hydraulic lifters, that started with the OM 603 I believe. But the original posters car does.

A diesel purge won't hurt, but I've never had long term luck with it. Makes the engine run smoother while the purge is going (probably due to the different combustion point than diesel) but any nailing always came back afterward. Dirty injectors are stubborn. Pulling the injectors and bringing them to a shop or sending them out for a rebuild is easy and relatively (to other repairs) cheap. One of the best things you can do for ANY old diesel.
No it doesn't but lifter tick will still sound the same, and my 3000GT/Stealth has hydraulic AFAIK.
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Old 07-31-2009, 11:31 AM
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thank you for the responses. I was not familiar with the term "nailing" but had seen it in the archives (I have literally spent hours reading), I got the jest of it from context. Any tap that sounds metalic is alarming to say the least. Thanks for the input, I wanted some indication that I wasnt pissing up a waterfall.

Thanks again, injector service is next.

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