Just acquired 1982 300SD - PeachParts Mercedes-Benz Forum

anhydrous7 · #1 08-25-2002, 06:27 PM

I finally feel like a member. On Saturday I purchased a 1982 300SD with 136K. The previous owner advertised the car as having a bad transmission. After talking to him, he said that the transmission clunked on deceleration. I decided to go and take a look at her. After driving the car, I experienced the clunking on downshift. I did not feel any slipping from the transmission. I decided to gamble and buy her. I was able to purchase the car for under $2000.

To make a long story short, and with help from 240 Joe, I purchased the car and brought her home. The car upshifted ok, it was just when you came to a stop that the car clunked as it shifted down.

After searching threads and other various sites, Joe and I came to the conclusion that the transmission was probably not bad but their was a vacuum leak or blockage.

I placed the vacuum tester on the "T" located on the main vacuum line coming from the vacuum pump. With the car idling, I had 22 to 23" of vacuum. I next placed the gauge on the Y that the vacuum line plugs into coming up from the transmission/modulator. I had 14" of vacuum at idle. When I cracked the idle, the reading went down to between 2 and 3". This is not to spec. I should have had 12 to 10" when the idle was cracked and the vacuum is supposed to drop linearly as the throttle is advanced. With this vacuum malfunction, Joe had me check the orifice in the T mentioned above. You should be able to take a 1/16" drill bit and push it through the orifice in the T. I was not able to do this. Eventually I put the drill bit in the drill and pushed with it. This offered more leverage and I was able to clear the orifice that was blocked/clogged with carbon.

I then placed the vacuum tester on the vacuum line going down to the tranmission to see if the line was good. I was able to hold 27" for the four or five minutes that I let it on the line. I then put reconnected everything and took it for a test drive. The car shifts wonderfully and the clunking disappeared. I will still perform the checks on the Bowden cable and I plan on servicing the transmission. As it turns out, the car was starting out in second gear due to the partial blockage in the T.

There are a couple of other minor issues with the car. The A/C compressor was locked up. The PO had taken off the belt. The trunk was damp in the fender wells on both sides. But for the most part, I ended up with a better than average condition, fairly low mileage car for a great price.

Searching the threads and doing your homework really pays off.

Thanks to all who contribute to this site. A big thanks to 240 Joe. His input is tremendously appreciated.

billrok · #2 08-25-2002, 08:43 PM

Just think, had it not been for the wonderful people willing to give of their Mercedes secrets, you may have paid thousands to get your new Benz fixed! I love this internet thing.

unkl300d · #3 08-25-2002, 10:44 PM

Way to go. How is the interior?
Color?

speedy300Dturbo · #4 08-25-2002, 10:44 PM

Let me know if you are in need of AC compressor parts

kerry · #5 08-25-2002, 10:50 PM

I don't know about your car, but my 77 300d is designed to start in second gear. It only starts in first if you push the accelerator down far enough to engage the kickdown switch or if you manually put the selector in L (you can even put it back in D before accelerating and it will still start in first).
Why Mercedes engineered this feature is beyond me. Can someone enlighten me? In a car that I can beat off the line with my moped, it seems as though always starting in first might be beneficial.

190D22 · #6 08-25-2002, 11:56 PM

It's for better fuel economy. I am guessing it also helps to not spin the tires in snow or slippery weather.

unkl300d · #7 08-26-2002, 12:49 AM

Yeah, the snow is what I have read.

anhydrous7 · #8 08-26-2002, 12:09 PM

The exterior is anthricite gray with a gray interior. Overall condition is not too bad for a 20 year old car. Leather is in good shape.

As far as the shifting, I am now getting three destinct shifts getting up to final cruising speed. I am pretty certain it is starting out in first. Prior to cleaning the T I was only getting two shift points.

I am still learning about this car. My next move is to service the transmission. Once that is complete, I will check the Bowden cable and the modulator to make sure they are set correctly.

#9 08-26-2002, 07:03 PM

They had to be talking about a manual transmission starting in second gear. Automatic transmissions should only allow the car to start in P or N.

240Joe · #10 08-26-2002, 07:33 PM

Boy that 240Joe must really be a nice guy.

Unfortunately, he can't find any used injector looping return line and he's looked everywhere.

240J

anhydrous7 · #11 08-28-2002, 10:09 PM

This car just keeps getting better. It drives like a dream. I had a small fuel leak at the #5 injector. I replaced one of the injector return loops on #5. This did the trick.

I also put Michelin X1's on the front and had an alignment done. The front end was right on. No adjustment was needed.

I still can't believe that by cleaning out the orifice in the vacuum T that it eliminated the shifting problem. Last night I went through the records in the glove box and found a reciept for the transmission to be checked out by an indie. The PO paid $123 to be told the transmission was bad and that it had to be pulled. I don't know if I should call the PO and tell him of my findings. It is probably better to leave sleeping dogs lie.

My next move is to service the transmission. I intend on putting synthetic ATF in. Does anyone have any experince with running synthetic ATF. I think I will go with Mobil 1. I did a quick search for synthetic ATF and did not find much. I am not trying to start a big debate. Just looking for feedback from anyone with some miles under their belt with synthetic ATF.