W126 brake problem - PeachParts Mercedes-Benz Forum

mark skeen · #1 01-09-2008, 10:07 AM

My 1987 420 SEL lost brake pedal - goes nearly to floor before engaging brakes. Checked and bled brakes without benefit. Red brake warning light stays on despite release of e-brake. Any ideas what has happened? Thanks, Mark

TX76513 · #2 01-09-2008, 10:18 AM

Is there any visible fluid leaking anywhere?

mark skeen · #3 01-09-2008, 10:23 AM

I didn't see any leaks, Thanks, Mark

TX76513 · #4 01-09-2008, 10:28 AM

Here are some ideas.

While you depress the brakes have a helper see if any of the soft line from the caliper to body hard lines are swelling.
OR
Pinch off the soft lines (vice grips) on each wheel position. If you have same symptom problem is most likely in booster or master cylinder. Then troubleshoot the master cylinder/booster. If problem ceases remove 1 clamp from each wheel until you identify the problem wheel.

I have made some assumptions that your fluid levels are correct, no visible leaks.

cdplayer · #5 01-09-2008, 11:15 AM

Quote:

Originally Posted by TX76513

Here are some ideas.

While you depress the brakes have a helper see if any of the soft line from the caliper to body hard lines are swelling.
OR
Pinch off the soft lines (vice grips) on each wheel position. If you have same symptom problem is most likely in booster or master cylinder. Then troubleshoot the master cylinder/booster. If problem ceases remove 1 clamp from each wheel until you identify the problem wheel.

I have made some assumptions that your fluid levels are correct, no visible leaks.

If these suggestions do not solve your problem, remove the vacuum line leading from the brake booster to the engine and inspect for cracks. Also check function of check valve in this line. Just a thought..

t walgamuth · #6 01-09-2008, 01:22 PM

I don't think you can pinch off the flexible lines without ruining them. They are not just rubber, they have spiralled steel in them.

You could be suffering an internal leak in the master cylinder. Replacement or rebuilding is the only option.

Tom W

TX76513 · #7 01-09-2008, 01:55 PM

It doesn't take much to close them off - not that you would want 1/8" gap in your vice grips.

lee polowczuk · #8 01-09-2008, 01:56 PM

i think your master cylinder is shot if you have no sign of leaks

TX76513 · #9 01-09-2008, 02:06 PM

Quote:

Originally Posted by lee polowczuk

i think your master cylinder is shot if you have no sign of leaks

A swelling brake line if fairly common on the 126. It's worth a check $14 vs $102

Hatterasguy · #10 01-09-2008, 02:38 PM

Its probably the master cylinder.

As for the E brake light it probably needs to be adjusted. You can take up the slack under the car where the cable attaches to that big metal thing, forget what its called.