Any 300SD Gurus: Newbie Needs Help! - Mercedes-Benz Forum

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post #1 of 3 (permalink) Old 09-29-2004, 07:08 PM Thread Starter
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Date registered: Sep 2004
Vehicle: 1985 300SD•2001 CLK 430•1988 560SL
Location: San Antonio
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Any 300SD Gurus: Newbie Needs Help!

I recently purchased a 1985 300SD. It is a very nicely maintained car with 223,000 miles. All guages, windows, sunroof work and the A/C blows quite cold. I DO however have a few questions about things that concern me and the knowledge of some of the "old timers" on this board will be very appreciated, so bear with my verbosity.

1. There is a rather noticeable vibration when braking. It occurs at the very end of braking cycle, just before car comes to complete stop. Also, it only seems to occur from stop above 40mph or so, not during low speed braking. The previous owner has meticulous records and has replaced all pads and the front rotors about a year ago. I don't really think it feels like brakes. There is no noise when this happens. To me it almost feels like a wobbly wheel, but can't determine what it is.

2. Cruise control doesn't work. Previous owner said he had all vacuum lines/wiring checked, but still no cruise. Any ideas??

3. Power locks don't lock doors, but do lock trunk and gas filler door?

4. What motor oil (weight and or brand) is recommended for this vehicle in Houston, TX area.

5. Does anyone know what proper idle speed is for the 85 300SD. Mine idles between 500-600 rpm. Seems a bit low and looks like a good deal of vibration around the air cleaner. When I slightly rev...up to about 800-900 rpm, it smooths out nicely. Should idle speed be adjusted up to 800-900 rpm??? If so, HOW do I do this?

Other than those things, and slightly oxidized paint, this car is GREAT!!!

Thanks Guys!!!!
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post #2 of 3 (permalink) Old 09-29-2004, 08:19 PM
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Date registered: Jun 2003
Vehicle: 1991 300 SE
Location: Lakeland, Florida
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RE: Any 300SD Gurus: Newbie Needs Help!

One: you should check for warped rotors.

Two: cc amp may need to be replaced or resoldered.

Three: fuse replacement fixed my door lock problem.

Four: Delo or Delvac 15w 40 CH 4 API rated oil or synthetic.

Five: you’re thinking gas engine, this is a diesel – the idle speed is correct but low idle vibration my be anything from worn motor mounts to excessive carbon buildup.

Post in the w126 forum for more answers.
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post #3 of 3 (permalink) Old 09-30-2004, 12:28 PM
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Date registered: Sep 2004
Location: Ft. Worth Tx
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RE: Any 300SD Gurus: Newbie Needs Help!

On the engine oil you need to find out what type of oil the previous owner was using and stick with it.
Diesels with this mileage can be very picky about changes in oil type.
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