300 SD Vibrating Like Washing Machine-PLEASE HELP!
 

I've driven my "new" 300SD about 600 miles now and I can't figure out what is causing a distressing but intermitten problem. The car, which I bought with 224k miles, sometimes VIBRATES at idle. It seems to be getting more intense. However, it does not do this all the time??? That's very confusing.

A couple of days after purchasing the car, I noticed this. I was advised that the brake discs might be warped, since I noticed it when braking, just before the car came to a complete stop.

I've had a brake job since then (new pads all around and rotors resurfaced). The problem did not re-appear for several days and I thought it was over. Today, when coming to a stop coming off a freeway ramp, it was vibrating again!! Today I noticed that even after coming to a complete stop, it was still swaying like an old washing machine...I mean you can see the hood star moving! When I put vehicle in PARK or NEUTRAL, it smoothed out. Idle speed is fine, even when vibrating, at around 850 or so rpm.

So what gives guys? What could cause this to happen SOMETIMES but not ALWAYS?

Another dissappointment: filled up today after driving 157 miles, and car took 9.5 gallons to fill up; THAT'S ONLY 16.5 MPG. Where's my diesel economy? This is confusing because when it's not vibrating, it runs extremely well and is a very clean car that's been well maintained???

Some things to check:

- condition of engine mounts and shocks

- IP primer pump handle is secure and primer pump is not leaking

- injector return lines are not soaked and leaking

There's a lot more to check but these are easy to check.

Sixto
95 S420
87 300SDL

How do you check the mounts???
 

Everything else looks OK, but how do I check mounts????

I would re-post this in the Diesel Forum. There are some really good diesel guys that hang out there...

There is an adjustment screw at the back of the injection pump (IP). Adjust it in until it smooths out. You may need a new one. It is called
the "rack damper screw." It has two nuts on it (one is a lock nut). Loosen them and screw the pin in clockwise. If it does not smooth out replace the screw as the pin inside it is spring loaded and the pin wears and the spring weakens over time.