One last try on this problem...sounds like a loose valve but isn't. - PeachParts Mercedes-Benz Forum

lietuviai · #1 11-18-2003, 05:33 PM

I figured I would give this section of the forum a try before I give up on it once and for all. My '85 300 D turbo, CA emissions model, has a sound coming from the engine that sounds exactly like one of the valves are loose. I have checked, adjusted and rechecked the valves and they are all to spec. The "click" is engine speed related and seems to be louder when fully warmed up. Strangely, the sound can be best heard from the drivers seat. I have not been able to distinguish the sound from all the rest of the sounds that from under the hood with and w/o a stethoscope. I have checked for loose, broken or leaking items and everything exteriorly on the engine appear fine. The car otherwise runs good and has as much power as it should. The oil pressure and coolant temperature are both normal. I have run out of things to check and I would like to try fix this problem myself before taking it to a shop. Is there any technical expert out there that can help me?
~DJ

engatwork · #2 11-18-2003, 05:57 PM

What do the timing chain/guides look like? Wonder if you are hearing the "kiss of death" chain noise? If it were mine and I confirmed that the chain/guides were good and it is running like it ought to I would just leave it alone

and run it. Change oil every 3-5k depending on your preference and rack up them miles.

lietuviai · #3 11-18-2003, 06:29 PM

When I had the valve cover off to check and adjust the valves, I checked the chain at the same time and it appeared nice and tight. I wasn't really able to check the guides/rails at that time as I couldn't get a good look at them but from what I could see they looked OK. The sound that I have doesn't appear to be coming from the front of the engine as I would expect a bad chain or rails to cause. But I could be wrong as I can't really tell where the noise is coming from with my head under the hood. When in the drivers seat, it sounds like the noise is coming from the driver's side of the engine. When I stick my head under the car, it sounds as if it is coming from the bottom end somewhere. The noise started about 4000-5000 miles ago. I have since gone through a couple of oil changes and I haven't noticed anything out of the ordinary in respect to the oil with no visible metal particles before or after the noise started. Is it possible that the tensioner is bad and is there anyway to check and adjust it? How should the rails look and what would be a way to get a good look at them without having to tear the front of the engine down?
~DJ

haasman · #4 11-18-2003, 06:38 PM

I would also check the vacuum pump.

Our old 240D made a bunch of noises similar to what you are describing right before the vac pump disintegrated.

Haasman

lietuviai · #5 11-18-2003, 07:16 PM

Quote:

Originally posted by haasman
I would also check the vacuum pump.

Our old 240D made a bunch of noises similar to what you are describing right before the vac pump disintegrated.

Haasman

Would it still work fine even if it was making noise and how long should it last? It's one of the last engine accessories that is still original.

haasman · #6 11-18-2003, 07:42 PM

lietuviai

>If< it is your vacuum pump and it is making the noise, it would work up to a point and then quit. How long ...... hmmm days? Hours?

haasman · #7 11-18-2003, 07:53 PM

Maybe it isn't mechanical .... if it sounds the loudest sitting in the driver's seat, check the firewall and see if there is a ripped grommet or seal or simply an opening that is allowing normal engine noise to reach the cabin.

Haasman

lietuviai · #8 11-18-2003, 09:02 PM

If that's the case, then maybe it isn't the vacuum pump since I've had the noise since last summer for about 5,000 miles or so.

lietuviai · #9 11-18-2003, 09:38 PM

Quote:

Originally posted by haasman
Maybe it isn't mechanical .... if it sounds the loudest sitting in the driver's seat, check the firewall and see if there is a ripped grommet or seal or simply an opening that is allowing normal engine noise to reach the cabin.

Haasman

That was one thing that I fixed just after getting the car back in March. I had some water leaks so I took care of any hole or broken seal that I could find. I think we can rule out any "normal" noises coming from the engine compartment.

mhingram · #10 11-18-2003, 09:45 PM

Get a automotive stethoscope, I find them invaluable in finding wierd noises.
m

lietuviai · #11 11-18-2003, 09:52 PM

Quote:

Originally posted by mhingram
Get a automotive stethoscope, I find them invaluable in finding wierd noises.
m

I borrowed one to check for my noise, it works as good as a wooden broom handle. Anyway, all the sounds I heard sounded the same, just a bunch of loud hammering varying in pitch and intensity. Those diesels are loud!

mhingram · #12 11-18-2003, 10:04 PM

did you check the diesel injector unit out of curiosity?
m

#13 11-18-2003, 10:45 PM

Just a thought - could it be piston slap? I had a F#$D with a V6 that had piston slap (just out of warranty of course) - sounded like a tappet tapping - ran it another 60K miles before scrapping it. If it is piston slap - thicker motor oil will make it less noticable.

afmcorp · #14 11-19-2003, 02:01 AM

no one has questioned the exhaust manifold or the exhaust system.

is the manifold on the right side (pass)? being it is a calif car does it have a heat riser valve in the exhaust? exhaust leaks have a ticking sound not quite like a ball stud but it is engine speed sensitive

just my .02$

tks
craig

lietuviai · #15 11-20-2003, 11:31 PM

Quote:

Originally posted by mhingram
did you check the diesel injector unit out of curiosity?
m

Do you mean the injector pump? How would I check it, since it seems to work fine. I didn't hear any noises coming from the IP. The injectors are another story. How could I check them?