W123 300d: Recent Brake Job, Brake Sensor Light flashing - PeachParts Mercedes-Benz Forum

KevRC4130 · #1 10-13-2010, 03:36 AM

Hey everyone,

I just had the front brakes done on my 84 300D (backs still have about 30% life left) about 2 weeks ago. Before the job, the brake sensor light on the instrument panel would illuminate under heavy braking.

So, after getting the brakes done, the light went away. But, a couple days ago, the light began illuminating again. Weird thing is that it illuminates when the brake pedal is NOT pressed. And it only comes on sometimes, it's not always on. And, when it comes on, it usually flickers/flashes (more of a 'loose wire' look than an intentional 'flashing', if that makes sense).

Any ideas?

One other thing: it's a SoCal car, and looks like it: no rust, water damage, etc. But, this problem started happening after a few days of rain. The car was not in any kind of flooding or anything, but I can't help but wonder if the water somehow got into the sensor or something. But, it should have had sufficient time to dry out but now, so I dunno...

Stretch · #2 10-13-2010, 04:12 AM

There are wear indicators fitted to the front calipers - take a look at them - clean them up if necessary. That's where I'd start to look...

...did you replace these sensors with new brake blocks?

fruitcakesa · #3 10-13-2010, 08:16 AM

The brake indicator in my 81 240 kept coming on due a leaky clutch MC.
You probably have an auto trans though...

tangofox007 · #4 10-13-2010, 08:38 AM

The brake wear sensor operate by simply completing the ground circuit through the rotor when the pads wear thin enough to allow for same. Any other short to ground will do the same thing. The pigtails at the caliper would be the prime suspects.

MattBelliveau · #5 10-13-2010, 10:14 AM

In addition to the above, check to make sure that you're e-brake pedal doesn't have any play in it (maybe the springs are tired, and the pedal is moving up and down on it's own). That would also illuminate that light. Probably not your problem, but still a possibility.

okyoureabeast · #6 10-13-2010, 10:21 AM

Quote:

Originally Posted by tangofox007

The brake wear sensor operate by simply completing the ground circuit through the rotor when the pads wear thin enough to allow for same. Any other short to ground will do the same thing. The pigtails at the caliper would be the prime suspects.

*2

Those little wires should be replaced everytime the pads are done. Mine fell apart when i did my last brake job.

tangofox007 · #7 10-13-2010, 10:27 AM

Quote:

Originally Posted by MattBelliveau

In addition to the above, check to make sure that you're e-brake pedal doesn't have any play in it (maybe the springs are tired, and the pedal is moving up and down on it's own). That would also illuminate that light.

No.

bluebird · #8 10-13-2010, 12:40 PM

You state that you had the brakes done, did the people that did the job replace the brake sensors or did they reuse the sensors that were there previously? If they reused the original brake sensors that could be the problem.

codraro · #9 06-20-2011, 07:29 AM

I just did my front brakes on my 1982 300d and I did not replace the sensors
Now the brake pad sensor light flickers and the radio sounds like there is static relitive to the rpms
I will order new sensors and see if that solves theh problem

brakeengr · #10 06-20-2011, 09:31 AM

I just unplugged the wires near the passenger side firewall in my 82 300D- no brake light anymore. Of course, I get to keep a lookout to make sure the pads are not worn off. Figure brake performance/ pedal feel will be ample warning....

vstech · #11 06-20-2011, 09:36 AM

Quote:

Originally Posted by brakeengr

I just unplugged the wires near the passenger side firewall in my 82 300D- no brake light anymore. Of course, I get to keep a lookout to make sure the pads are not worn off. Figure brake performance/ pedal feel will be ample warning....

nope.
you will be unaware of issues until metal touches the rotors...
put the wires back on...

vstech · #12 06-20-2011, 10:09 AM

Quote:

Originally Posted by MattBelliveau

In addition to the above, check to make sure that you're e-brake pedal doesn't have any play in it (maybe the springs are tired, and the pedal is moving up and down on it's own). That would also illuminate that light.

to illuminate what tango is saying...
this will light up the BRAKE warning light, not the Bake PAD warning light...