brakes mystery

[Rick007]

I've been struggeling with my brakes now for some time . They're squeaking and squealing drives me crazy .
I've changed about everything : Lines and tubes  , Booster , Calipers ( New ATE classic  )  , Discs , and Pads ( green ones ) , and still one rear caliper is sticking .
When i changed the pads after 4000 km from new , i found on one side the pads worn to the limit and the other ones still fine .
So one new caliper ( Right Rear )  is sticking …. But why ?  I socalled trained the caliper by pushing them open again and again and using the worn pad when braking , with no result .
I even pulled the half shaft because i thought it had to much free-play , but thats all in good order and renewed ( Bearings ) .  
Now i ask you could it be the valve in the back , the one that divides the rear brakes and limits the pressure when braking ? It is the only thing i still have original since the rebuild . And is there something to rebuild on that thing or is there a alternative ?

Hope someone can shed some light …

 

[Iva Biggen]

I would Replace the Rubber hose going to that caliper even though you said you replaced the lines???
As for squealing ,this could be a gob of things from dust, to the pads themselves not being of the same batch .
Textar was the oem pad for your car and they actually had some batch problems back in the day .  I HATE the NEWER pads that literally puff out clouds of black dust everywhere and that dust can get in the smallest  crack or fine line in any rotor... I use Wagoner pads with the gold back and have no problems . I believe they are WF734 rear and 736 for front or visa versa.

[Cees Klumper]

This is quite strange as it would seem you replaced everything that could cause it. I don't know how the proportioning valve works but I would expect it would affect both brakes, not only one. As suggested, the rubber hose must also be replaced but if that has been done perhaps you need to check the (new) caliper for possible defect.

[jameshoward]

Hi, Rick,

It may be worth taking the discs off the stub axle and just checking that the mating surfaces are perfectly clean and that you haven't trapped something in there, like a flake or paint or some dirt or grit, which could case the disc to rotate off axis. It happens some times. Just a thought, because it sounds like you've tried everything else.

James

[garymand]

 Your description: " i found on one side the pads worn to the limit and the other ones still fine."
The caliper and hoses are new on both sides?  Rotors badly warped, a new one is $50?  A crack or warp should be hearable as you rotate the rotor, it would snag a pad on one side and alternately on each pad. 

I think Iva is close.
Are you pushing the fluid back up the lines or are you opening the bleed valve and expelling the fluid when you push the pistons all the way in?  Normally I bleed the old fluid, but in this case keep the bleed closed and see what back pressure you get as you push the pistons in.  And use a big slip jaw pliers pushing evenly on the pistons so you know how it feels as you press.  The back flow should be similar for all four pistons.  Also are both pads in one caliper worn about the same?  (so both pistons are pushing too much?) 

I had a crazy plugged hose once that allowed one-way fluid travel.  It would let fluid go to the pistons but not back.  
You can get a rebuild caliper for about $60 or a good used one and substitute the whole caliper.  The car really pulled to one side when the brakes were applied.

[jameshoward]

Gary,

Sadly parts are somewhat and considerably more expensive in Europe.

JH

[Bonnyboy]

Rick,  I don't know what is in the compensator / regulator thingy or how it works and will leave that discussion for someone who knows the answer.   I will also assume that the caliper is in good nick.  

 I note that you say replaced the lines - did you replace all 6 pieces or just the two closest to the caliper.  I replaced all of the lines, 4 flexible and 2 solid lines, one of which hade been kinked and then sort of unkinked but was still kinked and cut all of them them up and found that the twoflexible lines leaving the compensator had internal swelling more than the ones at the brake ends.   They were all original to the car.  

Are the ends of the flare fitting dead on or are the holes off to one side.  Over tightening can muck up a flare end.

[Rick007]

Thanks for the Replies guys ,

in response to your suggestions :

* Yes i replaced every line from front to back , the same goes for the hoses .

* I checked the discs with a Dial ( don't know the English word for it hence the picture )  if they we're warped and replaced them twice already

* The new caliper pistons go in and out without much force , allthough i did not check the fluid level when forcing the pistons back in again, will do that first

* Then there's the brake hose on that side , i suspect , although i replaced it with a new one , this could maybe a faulty one and i will replace it just to be on the safe side.

* The pads we're the original ATE ones but i now replaced them with ERB green pads , they supposed to give less dust .

* Does my car pull to a side ?   No, thats the strange thing the car does not pull to a specific side . I had my brakes checked at a Mercedes mechanic after leaving Willingen last time and they checked out fine .
  They did the obvious and packed the pads again with paste . Pads slide in and out effortless.

So first thing will be to check the fluid fluidlevel when pushing the pistons in and replace the hose on the culprit side.
Before i forget it only happens when brakes are hot , so when cold there's nothing wrong and it will start after a 5 minute drive and hard breaking.

Yes Cees indeed that was my thought also. If the Proportioning Valve was blocking something it would affect both wheels . But after replacing about everything you start to wonder. 

Oh and Gary , a rebuild caliper costs around 200 Euro over here, and a new ATE classic will set you back  € 250,- . So i think for such a small difference go for the new ones.

will keep you posted …




I

[jameshoward]

You didn't mention checking that the discs are correctly mated to the axle stub, Rick. Even if you've replaced them, there could be something trapped on the mating surface which could cause the discs to run out of true. Costs nothing to check!

[Rick007]

Ok James now i know what you mean ….your right i will check that also ..

Thanks !

[Iva Biggen]

Both rear calipers Need to be of the same Brand. Preferbly ATE . if they are Bendix or Girling I would use them for trot line weights and get ATE'S