Hi,

I just acquired an 83 300D Turbo, 220k miles. I was able to get it for about $500, and it is in fair condition, but the brakes are bad.
Symptoms: pedal goes nearly to floor with little pressure, and low braking effect. Pumping the pedal helps just a little. Master cylinder is full with no obvious signs of leaking. Between the m/c and the booster, there are signs of a previous leak (paint stripped from the booster), but there does not seem to be a leak now; perhaps it was fixed previously. I had to drive the car home mosly by downshifting and the e-brake.

At this point I have not yet jacked up the car and removed the wheels, because I would like to have a systematic plan of attack, and perhaps have parts ready, e.g. brake hose, caliper or caliper kit, m/c, fluid, etc.

I know there are other threads about brakes, and the impression that I get is that it can be anything. But can someone give a step-by-step approach so that I don't have to replace the whole system?

Many thanks in advance.

J. S. Park

Not a full, step-by-step but a "pretest" if you will:

1. make sure the fluid is REALLY full. The rear calipers are only fed if the fluid goes over a partition in the master cylindr reservoir. This has fooled many experienced mechanics, so look very carefully. Top off and view with strong flashlight.

2. Bleed the brakes, starting with right rear, left rear, RF and finally LF.

3. Put a vacuum gage in line with booster and see what vacuum you have

__________________
'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.

I believe you must separate the plan into two parts:

1) Determine why the pedal travels nearly to the floor and the brakes are basically non-functional.

2) Go over the system on each wheel (caliper, pads, rotor, hose) and determine what replacement parts, if any, are required.


Pete has given good advice for #1. Attempt to bleed all wheel cylinders using at least one quart of fluid. Be very careful (I just recently screwed this up) that the fluid remains full in the m/c and drains over to the rear chamber for the rear brakes.

If you cannot get the pedal to perform properly after a thorough bleeding, it's probably master cylinder time. This is the last resort.

After you have a properly functioning hydraulic system, then the issues for #2 can be attacked. There is no point getting any additional parts together until the hydraulic system is functioning properly.

Many thanks to all who replied. It turns out that one of you were right--the back of the reservoir was empty. So, I filled it to the neck, and used the coke-bottle method of bleeding (didn't need a second person). No leaks, and the brakes are good!

I did notice that the two front brake lines were new, so the PO must have had them replaced, and either he or his mechanic was fooled by the rear reservoir compartment when it came time for bleeding.

It's the first time I've done this, and it seems I was needlessly worried. Many thanks again for your guidance.

J. S. Park

Yep, that rear chamber has bitten more than one of us.

Glad you've got it working properly.

Help is what we do here.