Hello everyone. I just purchased a 1975 240 D, 4 cylinder, 4 speed manual transmission, this past weekend. It has 134k miles on it and seems to be in (relatively) sound mechanical shape. The PO was not any kind of mechanically inclined, but has in the past 2 years had new brakes and a new transmission put in. I say that he is not mechanically inclined because he noted that a light on the dashboard (the brake light) came on intermittently, but he did not know what the light was for and thought that the car ran fine anyway. I filled the (almost empty) brake fluid resevoir and the light has not come on since (except when the emergency brake is on).

My question is this: what should I expect from the brakes? Before filling the resevoir, the pedal was not very firm and sunk quickly, requiring repeated pumping to stop. Now that I have filled the resevoir the pedal is much firmer, but it starts to sink after about 2 seconds of applied pressure, and I still need to pump it a few times for each stop. I don't know if this car has power brakes or not, but this does not seem like fine German engineering to me. I have a Jeep of similar era (1977 CJ5) with power brakes, and while it does not stop on a dime, it hasmuch better stopping power than this does, and does not require pumping. I think it is possible that there is air and/or a leak in a brake line, so my first thought is to bleed the brakes while adding more fluid. What are the opinions out there? BTW I used Prestone synthetic DOT 3 brake fluid.

Thanks in advance, Alex.
BTW, I freaking love this car.

 

I have owned a '76 300D, same chassis. One of the best handling and brakingsedans of that era. First inspect the pads front and rear. Replace thin pads, they are cheap and easy to replace.Now bleed the system completely. Start at the rear wheels have someone pump the brakes ( pump slowly), add fluid to keep air out during the process. Keep at each wheel until the new, clean fluid comes out. Repeat the process at all 4 wheels. The pedal should be firm now. The braking performance will impress you.
Good luck.
PS: when bleeding, look at the rubber flex lines to the calipers, if cracked or soft they will impart a soft feel to the pedal, and uneven braking. When in doubt replace any part.

 

I was mistaken, this vehicle does have power brakes. Pads look good.

I bled 3 of the four wheels last night, but broke off the nipple on the reardriver's side. Oh well, gonna have to get that out of there and replace it, then bleed the system again. Got a lot of really old rust-colored fluid out of the other 3 though, and that improved the pedal quite a bit, but it will still sink and needs pumping, so I think that I may still have air in that last line that needs the nipple replaced. Will just have to re-evaluate after that. Alex