Brakes: How to diagnose?
 

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

If it was my car I would do the following steps

1. Pull off all the wheels and look for leaking calipers or connections
2. Bleed the brakes starting with the right rear,left rear, right front,left front
3. if no solid brakes you could have an internal leak in the master cylinder
4. Replace master cylinder

Repeat step 2.

of course check for pad wear while you are there but that would not produce a soft brake

Post results so we can learn from your experience

Also check brake disk condition and thickness while you are down there. Follow the above advice and you should get the job done.

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