Please help me identify this noise! - PeachParts Mercedes-Benz Forum

cornblatt · #1 09-25-2007, 02:01 PM

I'm trying to track down this tapping/clacking noise coming from my car (a 1984 190D-2.2). The thing that makes it difficult is that it's hard to hear it when the hood is open because other engine sounds drown it out. It's easiest to hear when you're beside the car with the hood closed, so I'm having trouble pinpointing the source.

So, I thought I'd see if anyone here has any ideas... here are some mp3 files of the noise:

beside the car with the hood closed
above the engine with the hood open (you probably won't be able to hear the tapping sound very well in this one)

Any ideas you have would be greatly appreciated! The car runs well - the noise just irritates me and doesn't seem right.

jkoebel · #2 09-25-2007, 02:30 PM

AC compressor, maybe? Its hard to hear.

DieselAddict · #3 09-25-2007, 03:00 PM

I can hear it clearly. It could be a lifter or rod knock. Is it there just at idle or does it increase with engine speed?

jkoebel · #4 09-25-2007, 03:20 PM

Quote:

Originally Posted by DieselAddict

I can hear it clearly. It could be a lifter or rod knock. Is it there just at idle or does it increase with engine speed?

What a difference listening environment makes...on my good headphones, duh.

No idea what it is, personally, but it is there now, lol.

2.5Turbo · #5 09-25-2007, 04:04 PM

Sounds like a clogged or bad lifter to me. Mine has a lifter that won't shut up at idle but goes away when the engine is revved. It'll start ticking at a stop light but will go away upon takeoff at about 2000rpm. Then at the next stop it will come back after about 10 seconds of idling. I've got some Mobil1 in there now to see if it quiets it down. Next step is to open up the valve cover and check things out.

Cervan · #6 09-25-2007, 05:15 PM

could be an injector with a bad spray pattern.

Phil · #7 09-25-2007, 05:58 PM

Is the AC on or off when it is making the noise? Does it make the noise both with the AC on and with the AC off? My AC compressor makes a lot of noise at idle but it goes away when I start moving.

cornblatt · #8 09-25-2007, 08:07 PM

Thanks for your feedback. This is great!

Quote:

Is the AC on or off when it is making the noise? Does it make the noise both with the AC on and with the AC off? My AC compressor makes a lot of noise at idle but it goes away when I start moving.

The AC is off (I never use it). I checked the pulley on the AC compressor with the belt removed, and it spins freely and quietly. I can check again with AC on just in case though.

Quote:

could be an injector with a bad spray pattern.

To confirm this, would I need to remove the injectors and take them somewhere to get them tested? If I do this, do I need to replace the washer-like thing that sits underneath?

Quote:

I can hear it clearly. It could be a lifter or rod knock. Is it there just at idle or does it increase with engine speed?

It is there at increased engine speeds as well. It does not increase in volume; it just ticks more often the faster the engine turns. It either goes away above 2000RPM or other noises drown it out.

Quote:

Sounds like a clogged or bad lifter to me. Mine has a lifter that won't shut up at idle but goes away when the engine is revved. It'll start ticking at a stop light but will go away upon takeoff at about 2000rpm. Then at the next stop it will come back after about 10 seconds of idling. I've got some Mobil1 in there now to see if it quiets it down. Next step is to open up the valve cover and check things out.

So yours makes the exact same sound then? I've been using Mobil1 for 4 years... I did check the lifters earlier (http://www.peachparts.com/shopforum/showthread.php?t=200501) as I suspected them, but not having heard a bad lifter before, I wasn't sure if I was on the right track or not. I tried putting my ear over different cylinders to see if I could locate a noisy lifter but I couldn't.

Additional opinions/advice would be greatly appreciated!

DieselAddict · #9 09-25-2007, 08:35 PM

Quote:

Originally Posted by cornblatt

It is there at increased engine speeds as well. It does not increase in volume; it just ticks more often the faster the engine turns. It either goes away above 2000RPM or other noises drown it out.

It's probably a bad lifter then. Bad injectors typically don't show up at both idle and higher RPM's unless they're catastrophically bad. Typically a bad injector would be louder at higher RPM's and quieter at idle. You might just have to bite the bullet and replace the lifters.

jbach36 · #10 09-25-2007, 09:01 PM

I haven't heard the file you sent, but from the replies about spray patters, etc., might want to try some diesel kleen. It'll take 2+ tankfuls to see any difference, but it definitely quieted my car down.

jeff 1991 300d, 111k

2.5Turbo · #11 09-25-2007, 09:56 PM

To rule out the bad injector possibility, crack the injector lines one at a time and see if it goes away. If it does with one of them, then that one needs to be looked at. If none of them make it go away, it's most likely a lifter.