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1985 Mercedes-Benz 500SEL
36 Posts
Discussion Starter #1
I understand that all of the pre-86 300 class diesel engines are the same, so I figured it wouldn't be a big deal to skip the 126 forum, and come here.

I have found a good-ish condition 1984 300SD with at least 237k miles (the odometer is broken). When the vehicle was started, It did so quickly, and I noticed no smoke coming from the tailpipe. Everything seemed pretty sweet with it, until I started driving the thing around.

At about 15-20 mph, I noticed the car surging as if I were pressing down on the accelerator, and releasing, in a smooth fashion. The problem seemed to go away after a couple minutes of driving. I don't feel like the transmission was at fault -- it seemed to shift very smoothly (judging by the fact that I couldn't really tell it was shifting at all, except for by the RPMs). Even that archetypal clunk as you shift into D for the first time after starting the vehicle was very minor. I was impressed!

I need help with a possible diagnoses with this surging issue, as well as a recommendation for price. I am being very cautious with this purchase, as my last attempt to get a 500SEL gasser ended up a very expensive mistake (I -don't- want a repeat of that).

The good:
-Aftermarket stereo
-Seems to shift very well
-Paint is -not- fading, but is a bit dull -- I see some polishing/waxing in the future. Black paint on black leather (driver seat is pretty ugly, but still very supportive). Overall, vehicle looks very keen.
-Interior is good. Clean carpets, decent wood. Trunk seems leak-free.
-Much tread left on tire (will check for dry-rot on second visit).
-Brakes are very smooth and firm.

The bad:
-Surging issue
-Climate control will require much work (blower motor, probably compressor/etc, perhaps climate control unit refurbish (you can resolder these, right?)). Blower motor could also be as simple as a fuse, too, I guess. In any event, it's not blowing air; it just emanates warmth all of the time.
-Driver seat (not a big deal)
-Possible very high mileage
-Belts are squeely.

I am kind of bad at car shopping, and I neglected to check the working status of the windows/sunroof. It was raining today, so I'm fairly sure the sunroof does not leak or anything. I think the vehicle is worth pursuing, but only if the surging issue isn't serious and is most likely easily fixable. The owner is asking $1850, but I would like to get it for cheaper, given the surging issue and the climate control. What would be a fair price, and what things should I check to help make a more informed decision? I will return tomorrow or the next day with a former diesel-benz owner and a car guy to help me further check it out. I would like to get it for $1400 or lower; am I being unreasonable? Or perhaps too generous?

What should I expect to service/check/repair right off the bat? I'm thinking in terms of this diesel purge I've been reading about, a valve adjustment, filters, etc. I should have enough money to flush all of the fluids, too. Typically, how much should I expect to pay for a valve adjustment, anyways?

Thanks for reading!

1984 300D
5,070 Posts
The surging issue could be something as simple as an Air Leak or the Injectors need service or rebuilding.
I am saying the above because you said the surging goes away after the car is driven awhile.

But for the rest; if someone gave you the Car for free it could easily turn into "money pit" if you cannot do the repairs yourself.

You need to get under the Car and inspect anything made of Rubber; Oil Cooler Hoses, Transmission Cooler Hoses, Boots on the Rear Axles, Motor Mounts, Transmission Mount and the Flex Discs that take the place of U-Joints on the Drive Shaft.

As an example of a typical repair job cracked Boots on your Rear Axles. Someone has to remove the Axles and replace the 2 Boots per Axle (If the Axles are badly already making noise or contaminated with dirt you may need to replace them) or pay for a complete new or rebuilt Axles. Who would be doing the above for you.

Even when you do-it-yourself like when you replace a lower Control Arm Bushing you find that to use the typical Coil Spring Compressor is dangerous. I was careful and managed to bend my Spring Compressors up. I ended up haveing to make a Spring Compressor to do the job.
(The Original Klann Coil Spring Compressor made for the job is over $365. The Asian made copy is about $190.)
Replacing a bad rear Wheel Bearing requires a special Pin Wrench and a Dial Indicator with Magnetic base. And so on.

So far I have been able to do all of my own work on My Mercedes. But, I view it as a Hobby Car.
When something goes wrong with it the Car ends up sitting in the Drive Way until I can gather resources to fix it at a resonable cost.
This means I cannot count on it as my sole transportation.
I would look at the below links and you can see the types of repair issues others are dealing with and the sill level it takes to fix them.

Repair Links
DIY Links by Parts Category - PeachParts Mercedes ShopForum

PeachPartsWiki: Do It Yourself Articles - Mercedes Vehicles
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