Hi all,
I recently purchaced an '87 300D with 220,000 on the clock. The A/C was not working when I bought the car. I added two cans of R-12 and the die to begin to find the leak.

The air blows cold now, however, with the A/C on, the transmission shifts much harder and downshifts to 3rd gear with only a very slight increase in throttle pressure over 60 mph. It is then very reluctant to shift back to 4th and almost requires a quick move of the shifter to neutral and then back to drive.

Oddly, I pushed to full throttle on one occasion with it "stuck" in third and it downshifted to second at about 65mph. Tach went to 5100rpm! VERY SCARRY !!! I had to let completely off the throttle to get to third and then coax it into 4th. Next slight grade, roll in 1/2" of additional throttle and back to third.

I have studied the previous threads and have a rudementary understanding of the Bowden Cable and the vaccuum modulator but did not find this specific problem.

Two questions...

1) Why would the car run so well without A/C and have this problem with it functioning and on.

2) Is this more likely vaccuum related or Bowden Cable?

Any help is greatly appreciated. I am really looking forward to getting her road trip ready. This is my 4th Mercedes but my first Diesel.

BR,

Steve (8C>

Hi. I have the same car.'87 300D. LOVE IT!There are a few things you should look into. 1st I would look at the A/C compressor.If it was in need of service there's no telling the internal condition.It might still work but if it is starting to sieze it could get ugly.
2nd,when I first bought my car it was sluggish all the time.Off the line,passing,accelerating up a hill,ect. I was sort of stumped but having diesel knowledge I knew one thing for sure,lack of AIR or FUEL or BOTH will kill a diesel.Soooo I spent $60. and changed all the filters,Air,& both primary,secondary F.F.The difference was night and day.I can lay rubber from a stand still and chirp the tires going into 2nd gear.She pulls to almost 70mph before hitting 4th.(if I desire).I'm getting 30mpg around town and 35-38mpg hwy.In summer of course.
Finally I bought a can of lubromoly diesel purge which you run straight from the can to the injection pump and that smoothed out the rough ide when she was cold.I bought her from the original owner with 111K.She now has 130k.just starting to get broken in.I figure with close maintenence My 12 year old daughter will be getting her when she's 16.
I would also change the tran fluid/filter and go with the Redline synthetic.It may cost a few $$ but I have heard good things about it helping trans shifting problems.Good Luck. JOE

Yuo have a vacuum leak in one of the components that regulate the airducts under the dash.

When you turn the A/C on some valve opens up and lets all the vacuum out that the transmission needs to shifts as it is supposed to do.

This can be tricky to find.

For a start if you look here
leak searching by mercedes
You'll find a pdf from the service cd.
Don't know if it's to any help.

__________________
/Per

MB E300TDT -98

Per and Joe,

Thanks so much for the replies!

Per, you were right and I would rather be lucky than good! Based on you suggestion, I went out, opened the hood and found a vacuum line that was orphaned near the master cylinder as shown in the picture that you were kind enough to provide. I reattached it to the firewall and during the test drive happily rested my right foot on the the top of the kickdown switch at 80mph in 4th gear.

Surpisingly, the car also seemed to run alot cooler with this BIG vacuum leak fixed???

Joe, I have purchased all of the filters and fluids to do as you suggested and will do the major service this week. I have not found the Diesel purge yet, but I will before the week is up. Getting the tires to turn over is amazing! I'll let you know how it goes.

On a side note, as I said, I have a '95 E420 which I love. My wife cannot believe that I can enjoy the diesel equally, but I think I will. I love the engineering and simplicity of the diesel engine. I have a 25hp Kobota diesel tractor and it is the most reliable piece of equipment I have ever owned. Certainly, downshifting to second at 50 mph and dissappearing in the E420 is a thrill but there is something equally thrilling about the effecient power and torque of the diesel (not to mention the wonderful sound).

Thank you both again. I am certain that I will have other questions for this terrific forum as I bring the car back to perfect condition.

Best Regards,

Steve (8C>