Engine vibrations - Page 2 - PeachParts Mercedes-Benz Forum

psfred · #16 09-17-2002, 11:14 PM

Thanks Denrac!

My 300D is an 87 and my brothers 300SDL is too -- we both have a resistor plug.

Rough only in reverse seems like engine mounts, tranny mount, or flex disk? to me -- probably not running rough. If it is, it may be related to the electronic idle control, and I cannot help with that. Probably means a rebuilt pump (this is NOT a $200 repair, more like $2500).

Peter

Denrac · #17 09-17-2002, 11:45 PM

I would try the engine mounts before the IP rebuild. My car has symptoms almost identical to Jassper's, although they praticaly disapear when I put the the transmission in neutral. No idle speed variation is perceptible when they occur. The vibration seems somewhat related to the inclination of the car. I'm planning to change the engine mounts sometime next month. I'll keep you informed.

Jassper · #18 09-18-2002, 11:02 AM

Hello Den,

the car in question is an US 1992 model. I gather from your post (although slightly confusing) that there is no electronic control device for idle on it then.

Do you also mean to say that some models have both the electronic device as well as the adjusting screw?

Jassper · #19 09-18-2002, 11:20 AM

Hello Peter,

thanks very much for the info. The mechanic told me the pressure valve holders were something different. He probably wanted to overcharge me for the job. Since the leak is no more and this was (according to your info) no internal leak, I don't find it necessary to have the IP rebuilt.

The car is a turbo alright. As for the idle adjustement I asked a mechanic while at MB and was told to adjust idle the way I did.

A rebuilt IP costs really $200, here in Slovakia

$200 cover labour for testing, adjustment, cleaning and resealing with new set of seals. The price of seals already included. Of course you need to bring the IP along. According to what you wrote the lever should stay down overnight. This is what I was afraid of. It only holds vac for several hours. If your lever stays down indefinitely then there must be some leak. I don't think the headlights influence this. Unplugging the headlights caused nothing to the lever, they must be 2 independent circuits. Also yesterday I installed a one-way vac valve to the headlight circuit.

As for the engine mounts - thanks for the info, will give it serious consideration to replace them. I will ask for details when I order them at the local MB shop, they are always very helpful with this.

Jassper · #20 09-18-2002, 12:40 PM

Hello Zoon,

I recently underwent the task of chasing down leaks in my vac system, and I got a lot of good pointers from the archives here. I found that the plungers on the door lock bellows were cracked and leaking, so I fashioned a fix with yellow dishwashing gloves. I now have 100% vacuum on my 300D, and it's a pleasure to actually USE the door lock features the way they were meant to be.

Hmm. Do you think the central locking system is interconnected with the rest of the vac system? My old 123 used to have a vac reservoir that operated the locking system, this 124 has an electric motor underneath the rear seat, when you lock the door the motor will activate for a few seconds and suck the locks close. That's some progress I would say - you still have vac driven locking system yet there are no leaks from the reservoir - simply because there is none, the electric motor produces a short vacuum when needed. It doesn't need vac from the engine, that is why I think the systems are not interconnected.

Denrac · #21 09-18-2002, 08:41 PM

Jassper :

I'll try to "slightly deconfuse" my post ! (but my less that perfect english can be a problem). All 602/603 engines have electronically controled idling speed : the controler is a computer located near the inner firewall behind the battery (Electronic Diesel System control unit or EDS). That controler send a variable signal to an electromagnetic device fitted on the back of the injection pump to adjust the quantity of injected fuel. On 1986-87-89 models, there is an adjustable resistance to trim that signal and fine tune the idling speed. On 1990 and up models, there is not such a device : the EDS unit does the job on it's own. On top of that, all 602/603 IPs (I guess) have an adjusting screw to "mechanically" alter the idling speed. I guess (pure speculation !) that it is factory set for the mechanical tolerances of the IP and that it should not be used to ajust the idling speed of the engine. Doing that could trow the elctromagnetic device of the IP out of it's working range.

leathermang · #22 09-19-2002, 11:47 AM

Sometimes the factory has found and corrected problems with cars it has sold...everyone should plug their car info into one or both of these sites and see if there is some official cure already available for what ails one's car....

http://www.alldata.com/recalls/index.html

http://www.nhtsa.dot.gov/cars/

There are several " rough at idle " cures listed in TSB's... and some are just adjustments which were engineered for by the factory.. designed to be used after wear has occured....

Denrac · #23 01-06-2003, 03:02 PM

Last week I've replaced the engines mounts on my car. That was well spent money : chassis vibration at idle completely gone, smoother shifts and a car quieter at highway speed.

It was an easy job done in my driveway at 15 F. The old mounts were not teared, but they were half an inch collapsed. When shaking the old mount, the sound seems to indicate that there is no more hydraulic dampening fluid in it.

psfred · #24 01-06-2003, 07:55 PM

Yup, those are dead mounts! If you cannot see the tapered portion of the mount (on the bottom), they are shot. When they really get bad, even the lower rubber part can get driven under the steel cover on top, allowing the cover to thump on the frame.

Needless to say, bangs, thumps, rumbles, and vibration are all eliminated by new mounts, and this style is MUCH easier to replace than the older ones!

I've got the new ones for the 300TE, will be getting new ones for the 300D in a month or two.

Peter