850 brakes

Anyone any ideas and comments about this one. 1996 volvo 850 2 litre 20
valve. Sent it into the mechanic, brakes very spongy becoming harder with
the next press of the pedal. Mechanic bled the brakes (60 quid, does this
sound reasonable?) but pedal still low and although less spongy and more
efficient depressing about a third of the pedal travel but still harder on
the second press. Mechanic said it needs new discs as they are warped (I
will agree with this as there is the classic symptoms of a warped disk but
not severe). He says once the discs are replaced with new pads they should
be as I want them. Also he says that the calipers become 'lazy' with age and
they should also be replaced. In other words nearly all of the system
replaced except master cylinder, pipes vacuum and abs unit. I always
understood the 850 brakes were exceptional, they certainly were when i
bought the car 2 years ago. A comment on another chat forum suggested that
since the disks are warped, that they would push the piston back into the
caliper, thus making the first press feel 'soggy'. Also, anyone know
anything about drop links, symptoms of wear and replacement (how easy etc?
Any comments and suggestions gratefully accepted. Sorry for the longish
post! - Roy

 

I had the same problem last year on my 1996 850. On the first pedal pressure
the
pedal travelled far and I felt that there was little resistance and on the
second pedal
pressure it was ok. Found that my front disc's was below limit in one front
side and
this was caused by a slightly hanging (lazy) caliber. Changed the front
calipers and
the front discs and everything went like new again.

 

If the rotor is warped, it pushes the pistons back causing more pedal
travel. Wear does not cause this since the pistons should stay just
slightly above the surface no matter where that surface is if there is
no wobble in the rotor. Of course air in the line will cause sponginess
but that usually doesn't go away when you pump the brakes.

By the way, the main causes of warped rotors are improper torquing of
the lug nuts and high speed stops.

 

many many years ago when I drove cabs for a guy who used to swap around pads
and use retread tyres I had brake problems too .He employed a partimer on
the week end who flogged the car and the brakes were bad news on Monday .So
I found heating them up a bit and cooling them down slowly seems to remove
the issues ,he was an ex cop ex navy and ex security guy so he pushed the
cab hard .I owned several cabs new tyres (safer and cheaper in the long run)
quality brakes and if a part timer warped them a bit I made sure I heated
them up and slowly cooled them then if needs be had them machined .Keep the
brakes off the hot spot by just moving slowly at the lights just a few
inches so there is no extremly hot spot to warp them dont just stop and turn
the motor off the brakes will super heat one spot and problems will occur
..$60 quid to bleed brakes wow thats high .