Excessive Valve Train Noise? - Page 2 - PeachParts Mercedes-Benz Forum

pj67coll · #1 09-19-2003, 07:33 PM

When you mention the manual idle speed adjustment knob on the 240D's dash, do you mean the small flat knob on the left side of the instrument binnacle under the dials that you twist either right or left? If so The 300D's I've test driven both had this and I recall my cousin's two 300D's in Australia also had them. Or is there another "knob" of which I'm unfamilliar?

- Peter.

Lycoming-8 · #2 09-19-2003, 10:09 PM

pj67coll

That is the item. On US spec cars the 300D's had this knob on the dash until the turbo's were applied. After that they don't seem to have the knob. My '83 (with Turbo) does not have the knob, but even in cold weather it does not seem to need it.

mechmagcn · #3 09-19-2003, 10:49 PM

My 81 300SD always will stumble and stall in the first 30 seconds after a cold start if the RPMs are not increased slightly. After that it idles smoothly all day. I thought that this was air in fuel, but it restarts too easily.

unkl300d · #4 09-20-2003, 01:26 AM

lietuvai, my 300d had alot of nailing when cold to warm and sometimes on high acceleration when hot.Sometimes hard starts like yours.
It was the injectors.
They were replaced and it is quiet now.

Whatever

lietuviai · #5 09-27-2003, 08:06 PM

Quote:

Originally posted by unkl300d
lietuvai, my 300d had alot of nailing when cold to warm and sometimes on high acceleration when hot.Sometimes hard starts like yours.
It was the injectors.
They were replaced and it is quiet now.

How much did it cost for new injectors and how much of a job was it?
I somehow didn't think the injectors could be wearing out at 218K miles but this is the first Mercedes I have ever owned.

unkl300d · #6 09-28-2003, 04:00 PM

Well, assuming you really need injectors, my rebuilt BOSCH injectors were about $56-60 each and the labor to replace all of them was about $75.
Fastlane sells them for maybe less. Some people claim that the rebuilt Bosch injectors can sometimes be defective. See archives. I've had no problems.
My injectors were replaced under factory warranty when the car had about 5K miles or thereabouts. Because of noise.This last time they were replaced at about 145K miles.

lietuviai · #7 09-28-2003, 08:24 PM

Quote:

Originally posted by unkl300d
Well, assuming you really need injectors, my rebuilt BOSCH injectors were about $56-60 each and the labor to replace all of them was about $75.
Fastlane sells them for maybe less. Some people claim that the rebuilt Bosch injectors can sometimes be defective. See archives. I've had no problems.
My injectors were replaced under factory warranty when the car had about 5K miles or thereabouts. Because of noise.This last time they were replaced at about 145K miles.

Right, assuming it is the injectors. Right now I'm keeping my fingers crossed that it's the valve adjustment. I checked and readjusted the valves to be exactly at spec yesterday. I won't know for sure if this will make a difference until after I have driven the car for a while and give the adjustment a chance to wear in. The noise was most noticeable after the car had been thoroughly warmed up. The noise occurring after warming up tends to make me think that it might not be the injectors but I could be wrong. I've even thought about a worse case scenario, a rod bearing going out. I had an old Cadillac many years ago that had a loud tap when it was warmed up and it was a rod bearing. The Benz on the other hand does not make a loud tapping sound. It's more of a tick (but way louder) that sounds like an old wind up alarm clock.

lietuviai · #8 09-30-2003, 06:48 PM

Well after driving the 300D for a few hours today the "valve" noise is still as noticeable as ever. The noise was just as obvious cold as it was hot. It seems to runs fine but the tapping bugs me. I guess I'll just have to stop by a garage that works on these things and have them listen to it.

leathermang · #9 09-30-2003, 06:56 PM

Why don't you check around your area and see if there are any nice parks or places to hold a get together? Let some others hear it... and compare it to their cars....

lietuviai · #10 09-30-2003, 07:16 PM

Quote:

Originally posted by leathermang
Why don't you check around your area and see if there are any nice parks or places to hold a get together? Let some others hear it... and compare it to their cars....

Sounds like a great idea, but I rarely ever see any other cars like mine around here. I might pass one by going the other way maybe once a week.

lietuviai · #11 10-19-2003, 12:10 PM

I have now ruled out that it is valve train noise. I adjusted the exhaust valves slightly on the tight side but the ticking sound still persists. Interestingly you can't hear it with the hood open but it can be heard while sitting in the car. At idle it is barely noticeable but when you give it some throttle it gets a louder. Also when driving, when you let off the accelerator it goes away but the sound reappears when you step on the accelerator.
I am totally baffled by this and am to the point if it is something truly serious such as something internal, I'm not going to worry about it since it will cost more to tear into the engine than what I could probably find another one for.
But if it's something simple I wish there was someone who can steer me in the right direction.

Kyle Blackmore · #12 10-19-2003, 01:30 PM

As someone suggested it could be an injector 'nailing' (I think that's the right term for this condition). Have you tried a Diesel Purge ? Before replacing injectors try running a can or two through the engine.Search Diesel purge for complete instructions,good luck.

JimSmith · #13 10-19-2003, 04:32 PM

lietuviai,

Based on your description, it seems throttle position, which controls exhaust flow, is a key to the volume of the noise. If this is the case, the exhaust and /or intake manifolds may be loose.

Check the condition of the intake and exhaust manifold fasteners. I am not familiar with a California set up, or the turbocharger support system, so this may not be of a great deal of value to you. These fasteners, a stud driven into the head and a copper nut, get a lot of cyclic loading from the roughness and general engine motion in normal operation. Part of the loading comes from the exhaust system being located by the body of the car and the engine being sort of floated on the mounts (at least that is the case on a 240D) resulting in significant relative motion .

The design makes the copper nut the sacrificial element of the system and it can become deformed. As a result the manifold can become loose over time and make quite a racket as it allows exhaust noise, unmuffled, to fill the engine compartment, and there is a knocking of the manifold against the head that goes along with it. One way to check is to get your hand near the manifold to head joint and have someone else rev up the engine. If you feel gasses escaping, you will have all the evidence you need.

There are other sources of noise under the hood that "go with engine speed" and another that is a frequent complaint comes from the air cleaner housing mounts failing. These little rubber mounts with embedded threaded rods fail when the rubber gets old and fails, which leaves the air cleaner housing free to bang into adjacent surfaces.

If these are not your problem, I would be inclined to use a stethescope while someone revs the engine, and poke around until you find the source. These engines are not really quiet, but they generally do not have loud metallic clanking or mechanically alarming noises. When running correctly they sound "perfect" meaning the noises are mechanically timed and regular, repeatable and even. Good luck and I hope this helps. Jim

lietuviai · #14 10-19-2003, 08:44 PM

Kyle, I haven't tried any sort of diesel purge in the system while owning the car but it is a start. I am hoping that the noise is no more than a bad injector. The car idles and runs well and seems to have enough power and I have not noticed any excessive smoking. It only has some occasional missing during start up while cold.

Jim, your suggestions of checking the manifold to head joints sound relevant as well, the turbo and oxidation catalyst were replaced about 40K miles ago and some of the studs were replaced. The manifolds are not too different from the federal models. I have looked the engine over in the past while performing various maintenance items and I haven't noticed any soot on that side of the engine. I have stethoscoped the engine while running and revving it up, but since there is so much noise coming from the engine, it's difficult to really tell if the noises I have heard are out of the norm. Interestingly enough the "ticking" noise appears to be coming from the passenger side of the engine from listening from inside of the car. I haven't been really able to hear the sound from listening in the engine bay. This sound is not unlike the sound a loose rocker arm makes hitting a valve.
The air filter housing is the only thing that entirely different on the CA model. It sits in the area just behind the passenger side headlamp.
I sincerely appreciate these suggestions from the both of you and I will carefully check them out before I give up and try to find a knowledgable MB mechanic look at it. The closest one to me is about 50 miles away.
~DJ

unkl300d · #15 10-19-2003, 10:07 PM

Another way to listen for noise is to drive along a wall.
For example, try a wall that divides two split level streets.

As you drive close along it, open your driver side window and stick your ear out.
The engine noise is amplified. (drive along the wall, not into it!!!-DOH)

My 300D engine ticks sometmes. I have had the valves adjusted and new injectors recently.

Only heard if I really listen for it. This is not nailing noise, however.

By the way, check your trans fliuid level. It may be at mini-minimum.
While refilling a trans on these cars( After service-topping off), I heard a slight 'ticking'
until I got that pint of fluid in to mark the minimum level.
(car idling and in PARK)