Question About Brakes

[HuDSoN]

Hi all

i have just started to notice that sometimes when i am braking, just before the car comes to a stop I get a 'erup!' noise, a slight pull to the right and feedback through the brake pedal, almost like it pushes back for half a second.

I have had the front wheels up and noticed that when you pressurise the brake system, the left side locks the wheel as you would expect but the right wheel can still be rotated. It is almost like they cant hold the pressure and retract back, however I have no leaks and fluid levels have not changed.

I stripped down the right brake yesterday.

The pins seem ok.

all the shims are present although a little worn but i dont get squeeking.

However I did notice that the bottom pot was out about 2mm more than the top.

I pushed them both out somewhat and they seem clean under the boots.

They were a little stiff but i would say not as much as other cars.

I also noticed when pumping the pots in and out that they dont seem to move together. first the bottom moves a little then the top and so on.

I am guessing this is a sticky caliper but my atempt to fix it made no difference at all.

Just wondered what you thought. Would like to make sure i get it right at min cost as lost job recently and have just had to fork out £450 for tyres, MOT, tax and ball joints.

your help is most welcome.

[kev dood]

sounds like one or both of the pistons are sticking a bit. You can get a reconditioning kit (either from lexus at a very expensive £65 or so, or from other brake companies for around 15-20).

Or you can buy a recon'd caliper from any car parts place (commnon parts are Brake international or Brake Engineering or Blueprint). All depends on how much hassle you want really, one would be a quick and simple swop, then other involves stripping the caliper down and cleaning it all up inside, removing pistons etc.

[HuDSoN]

sounds like one or both of the pistons are sticking a bit. You can get a reconditioning kit (either from lexus at a very expensive £65 or so, or from other brake companies for around 15-20).

Or you can buy a recon'd caliper from any car parts place (commnon parts are Brake international or Brake Engineering or Blueprint). All depends on how much hassle you want really, one would be a quick and simple swop, then other involves stripping the caliper down and cleaning it all up inside, removing pistons etc.

thanks

was going to go for a caliper, save time and stops the car being off the road. also means i will have a spare i can work on.

from other posts i assume this is the problem but what are the chances of having a problem else where in the brake system?

[kev dood]

Well, if the pressure can't be held and the pads "come back" off the disc allowign you to rotate the wheel still, then it could be the master cylinder? Do you ever have problems where you get a firm pedal and then sometimes whilst still having foot on the pedal, the pedal starts to sink?

Sometimes the seals can go in the cylinder - I would presume that if this was the case then as well as being able to rotate on front wheel, you should be able to rotate the opposite side rear also?? Don't the circuits cross or something?

Could also just need the brake fluid changing though!

But, if looking at the pistons, and it they are stiff in movement in and out and don't come out smoothly (not necessarily together mind) then I would say caliper.

Don't shoot me if wrong though!

[flyeris]

Well, if the pressure can't be held and the pads "come back" off the disc allowign you to rotate the wheel still, then it could be the master cylinder? Do you ever have problems where you get a firm pedal and then sometimes whilst still having foot on the pedal, the pedal starts to sink?

Sometimes the seals can go in the cylinder - I would presume that if this was the case then as well as being able to rotate on front wheel, you should be able to rotate the opposite side rear also?? Don't the circuits cross or something?

Could also just need the brake fluid changing though!

But, if looking at the pistons, and it they are stiff in movement in and out and don't come out smoothly (not necessarily together mind) then I would say caliper.

Don't shoot me if wrong though!

Would the reconditioning kit for caliper cylinders solve the sticking cylinder problem? :)

[HuDSoN]

Well, if the pressure can't be held and the pads "come back" off the disc allowign you to rotate the wheel still, then it could be the master cylinder? Do you ever have problems where you get a firm pedal and then sometimes whilst still having foot on the pedal, the pedal starts to sink?

Sometimes the seals can go in the cylinder - I would presume that if this was the case then as well as being able to rotate on front wheel, you should be able to rotate the opposite side rear also?? Don't the circuits cross or something?

Could also just need the brake fluid changing though!

But, if looking at the pistons, and it they are stiff in movement in and out and don't come out smoothly (not necessarily together mind) then I would say caliper.

Don't shoot me if wrong though!

i am now also thinking cylinder seals.

this isnt going to be simple like i was hoping is it :(

i was testing on my own so not sure how they are reacting if pedal keeped on but so far no other problems with the pedal.

may do a fluid change and see how that goes.

wondering if its this and the drop links, together making it look like a problem with the brakes. recently changed lower ball joints and some people have posted that the drop links showed thier problems once the ball joints had been changed.

[kev dood]

The caliper reconditioning kit only contains seals etc for the brake calipers, not the master cylinder. Taking one of them apart is a little more involved I think.

Ormi would know more as he is a Toyota Tech so could probably diagnose it better.

If you were only testing the brakes on your own, how did you manage to get out and see which wheel turned ok - without relieving the pressure on the pedal? If so, then the wheel that would move is the normal one and the one that didn't is more of a concern.

The drop link issues you mention won't cause any issues with the caliper piston movement.

Just re-read your post - 2mm difference in the pistons being out will be due to uneven pressure put on the pad - I bet if you then looked at the pads for that wheel you would see that have worn unevenly, i.e. an angled wear on one end more than the other.

But if you say you can push them in with relative ease then I would say your calipers are probably ok, in which case, as you say, you need to look elsewhere. You sure the ball joints were done OK?

[clifton 94]

hi we get cars in the workshop with sticky calipers and when we strip the caliper down the area between the seal and dust seal has rusted also rusts below the seals and this will make the pistons stick all you need is remove the seals and clean the area up with wet and dry and clean the seal area with a dremel with a wire brush attachment then when its rust free clean with contact cleaner and reassemble with new seals bleed system and road test hope this helps