caliper issue..weird.
Thread Starter
Pro
Joined: May 2001
Posts: 571
Likes: 5
From: usa
caliper issue..weird.
so I notice that my RR caliper doesn't appear to be working. rotor is pitted and still so what rusty, the other 3 are shiney fresh metal.
so I blead the RR, just a smidgen of air . so I pulled the pads and had the wife slowly push the pedal, I could see the pistons moving out toward the rotor.
there are no leaks that I can see.
why would this caliper not be braking like the others ??
so I blead the RR, just a smidgen of air . so I pulled the pads and had the wife slowly push the pedal, I could see the pistons moving out toward the rotor.
there are no leaks that I can see.
why would this caliper not be braking like the others ??
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
One possibility... (there are others)
If you have the OEM style rubber hoses, unless the steel line is crimped, the rubber hose is collapsed on the inside blocking most (but not all) of the line pressure to that caliper.
If you have the OEM style rubber hoses, unless the steel line is crimped, the rubber hose is collapsed on the inside blocking most (but not all) of the line pressure to that caliper.
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Do you have rubber hoses, or SS covered teflon hoses?
Pressure or flow? (they're different) If you replace the RR caliper with a pressure gauge, you can read pressure, at the same time, no flow.
Where did you get the "pressure" ? At the M/C or at that caliper?
If the other rear calper is working good, there should be full line pressure at both rear hoses but the flow on the RR could be insufficient to move the caliper pistons enough to engage the rotor.
Here is what I would do...
Pull the caliper & hose.
If the hose is OEM design rubber, replace the hose.
Disassemble the caliper and determine it's design- OEM or aftermarket, stainless sleeved or rusty.
Based on what you find, install new seals, boots and the o-ring.
Reassemble it all & re-bleed the lines.
Pressure or flow? (they're different) If you replace the RR caliper with a pressure gauge, you can read pressure, at the same time, no flow.
Where did you get the "pressure" ? At the M/C or at that caliper?
If the other rear calper is working good, there should be full line pressure at both rear hoses but the flow on the RR could be insufficient to move the caliper pistons enough to engage the rotor.
Here is what I would do...
Pull the caliper & hose.
If the hose is OEM design rubber, replace the hose.
Disassemble the caliper and determine it's design- OEM or aftermarket, stainless sleeved or rusty.
Based on what you find, install new seals, boots and the o-ring.
Reassemble it all & re-bleed the lines.
Thread Starter
Pro
Joined: May 2001
Posts: 571
Likes: 5
From: usa
when we bled the brakes we got a good "squirt" of fluid out of the bleeder.
then I pulled the pads and had my wife slowly push the pedal to see if the pistons were moving and they were.
of course now I am having a time getting the pads back in, think its just to hot out today.
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Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
I've had strange brake bias before. It might sound a little bubba but I pushed back all the caliper pistons while they were mounted. I used wood shims for construction (installing doors and windows). Make sure the master cylinder doesn't overflow. The pistons don't need to be all the way pushed in just a little.
Then I pulled them all out. Starting with the RR,LR,FR,LR. You'll see the brake fluid level drop in the MC. Top it off and then slowly start pumping the brakes pedal. (Like barely creeping down about 1/2 way) not to the floor. The pedal will get rock hard and then you can start the car to use the power booster to work it some more.
It works by getting all the air out and pumping very slow keeps the proportioning valve /check ball centered.
Its worked every time
Then I pulled them all out. Starting with the RR,LR,FR,LR. You'll see the brake fluid level drop in the MC. Top it off and then slowly start pumping the brakes pedal. (Like barely creeping down about 1/2 way) not to the floor. The pedal will get rock hard and then you can start the car to use the power booster to work it some more.
It works by getting all the air out and pumping very slow keeps the proportioning valve /check ball centered.
Its worked every time
Le Mans Master
Joined: Jan 2000
Posts: 8,918
Likes: 27
From: New Hill NC
This is in fact a weird problem if it is as described. You say the pistons move when you press the brake pedal. If that is the case, and the pads are not stuck, that thing is going to brake and the rotor will eventually be slick. However it is obvious to me that the clamping force is almost nill on that rotor. So something is causing the piston not to clamp. You need to go down that path to find what is wrong. Start at the MC make sure there is pressure. Go down the line to that caliper and look for kinks and any obstructions checking pressure as you go. Rubber lines are notorious for blockage, but usually that is an opposite symptom. Then to the caliper. Just some observations on what I see in the picture. The calipers are offshore replacements not GM. I would suspect them. The last person to install them didnt know or care about the correct hard line replacement position. That thing is over top and hanging out in a dangerous place. I would look at it for kinks that would stop flow.
Have someone press the brake and try to turn that wheel and compare the clamping force to the others.
Have someone press the brake and try to turn that wheel and compare the clamping force to the others.
Last edited by wombvette; Jul 25, 2013 at 10:12 AM.
Racer
Joined: Sep 2012
Posts: 420
Likes: 0
I've had a weird problem to after replacing the pads all around the car pulled to the right big time to the point my right tire would lock up. Replaced both front calipers and it's a lot better but still pulls a bit
I bleed the brakes all around
U might just need to replace your calipers and bleed brakes
I bleed the brakes all around
U might just need to replace your calipers and bleed brakes
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
You can crack the bleeders just to let a little air out but I assume you've done that a bunch of times already.
The idea is to forces all the fluid and air pockets up through the master cylinder. Also it pushes the check ***** back in the proportioning valve.
The proportion valve needs to stay reset. This is way you have to push the brake pedal slowly after removing the shims and don't bring it all the way to the floor. It might take 10 minutes of pumping slowly but when you get the pedal back, it will be firm
Good luck!
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Just put the pads back in and bleed that caliper again.
If you got "a good squirt" from that bleeder, then nothing should be obstructed.
The hose on that side may be deteriorated enough to expand, but that should lose pressure on both rear calipers, same with air.
Just sounds like the pistons are seizing in the bores of that caliper.
Don't be afraid to stand on the pedal as hard as you can to test and check wheel for rotation or leaking.
BTW, there are no check valves anywhere, if you have lots of fluid bleeding, you're golden.
If you got "a good squirt" from that bleeder, then nothing should be obstructed.
The hose on that side may be deteriorated enough to expand, but that should lose pressure on both rear calipers, same with air.
Just sounds like the pistons are seizing in the bores of that caliper.
Don't be afraid to stand on the pedal as hard as you can to test and check wheel for rotation or leaking.
BTW, there are no check valves anywhere, if you have lots of fluid bleeding, you're golden.
