just want some thoughts on the issue. 3 years ago, i replaced disks and rotors all around. this week, i just replaced my rear pads and 1 rotor after one of the rears threw the material and i got metal on metal braking.

my question to you guys is. the pads on the rear appeared to be almost worn completely, while the fronts still look like they have thousands of miles to go. I was under the impression that the fronts should wear out faster then the rears due to the proportioning of the hydraulic power between the front and the rear, and the weight in the front.

what are your thoughts on the issue.

BTW the vehicle brakes and is safe to drive

 

35 views and no thoughts,

I was thinking either a proportioning valve or the master cylander

 

Maybe the rear calipers are hanging up?

 

How about you tell us year model etc, we're not clairvoyants.
Help us help you!

Regards, Andrew.

 

Sounds like e-brake cable stuck or binding slightly causing constant friction. Could also be sticky caliper piston/s.

Were both sets of pads in the rear worn out evenly or was one side worse than the other ?

 

Sorry, about the lack of vehicle info. I'll add it to the the signature so i can forget about it always. 1989 740 gl. girling front calipers and bendix? rear calipers. the rears are the small square type with the little ears that the pins go through.

the pads were evenly worn on the rears, about 3/16 of material left. except for the one that failed and threw the material. I know this because I heard a loud clunk one day and could not find the source of the clunk until the brakes began to scrap metal to metal, and the pads up front had lots of material. The rear pins were looking a bit corroded when I pulled the pads and so I had them replaced. it could be that.

1981 240 dl. I don't think its the ebrake because there is a seperate ebrake drum system behind and inside the rotor for my model year. which the pads probably should be replaced, but I won't for now.

The main reason for the question was when I replaced the pads 3 years ago, it was basically the same situation. right rear, no material, left rear worn, and the fronts used, but in good order. I also bled the system the last time as well.

 

It sounds like the pistons are just getting hung up. Have you ever tried putting the rear wheels in the air and checking to see how easy they are to turn? Then cram on the brakes and then hop out and seeing if they still resist a lot. But just by that the problem has stayed and the pads and rotor are new it looks like the pistons are the problem.

 

I would not lean towards proportioning valve unless you brake failure light comes on as it is supossed to warn you in cases of uneven pressure distribution (Supossed to if it's working properly) thats the catch how do you know if it's working correctly. I would get some replacement rear calipers first then the proportion valve and replace them all at once since the system has to be bled in either case. Go with it for now and save the money for the parts then go ahead and do both.

Again that's just how I would do it.

 

I agree that a proportioning valve will cause a failure light. However, you should echek the light on teh dash works, just complete the circuit on teh proportioning valve switch with a piece of wire. Does the brake warning light come on pre start with the other warning lights?
Does the car have a single hydraulic line to both rear calipers (runs down to diff from floorpan then splits along diff to each caliper)? If so, sometimes the rubber hose can expand internally as they age, creating a restriction and holding line pressure for a short time every time you use the brakes. Also, any restriction in the single line part ( a partly crushed metal line) can cause the same problem.
Another problem could be driving style if it's an auto (dragging brake with foot).
3 years is a fair time for some cheaper brand brake pads and rotors can wear fast if pads are bedded in wrongly too. How do the rotors look? Even, glassy smooth with light grooves, or is the surface coarse, like metal is being pulled off the rotors?
Does the car have ABS? I recall that ABS vehicles have more rear bias on their hydraulic systems, somehow the ABS system requires more. If ABS not working, the rear brakes can do too much of the braking. My car was like this when I bought it with non working ABS.

Regards, Andrew.