Hi guys.... love the forum but this is my 1st post. I recently had the front wheel bearings changed as o had a rumble and vibration from the front wheels. The garage informed me that the two front brake calipers were also binding. I plan on getting these replaced this montj but i just wanted to check.... could this be a problem with the abs block ? I find it unusual that both would be binding rather than one or the other ??

Thanks for any help guys !

Duncan

 

Duncan, I would say to take the car out for a drive around the block. Drive for say 2 miles, getting up to 40 mph or so. Then park the car and place you hand near (not on) the rotor of each front wheel. If you notice a big difference in heat of the rotors, then this confirms a problem with the caliper that is hotter. Replace that one and then reperform this check to see if both calipers are at the same temp (roughly).

If both are at the same temp, then odds are the calipers are not the problem. This is where I would then be looking to see if there is a large temperature difference between the front and rear brake (fronts should be hotter, but not significantly). I would also look at your mileage and see if it has dropped off by say 3+ mpg. That would be another sign that your brakes may be an issue.

 

Hi Thermo, yea I have done all that and I am getting both wheels feeling hotter than the rears and hotter than I have felt them before . I know the callipers are binding but I am worried it may not be an issue with the callipers but with the ABS block. I have heard of this happening on x types and it is an expensive part, if it was just one calliper then I may be more inclined to just go with the calliper but 2 at the same time !?!? seems strange that both should be at fault. and yes the MPG is a bit higher than normal.

 

Duncan, you can replace the ABS module to the car for not too much. I have heard of a few issues like this in the past. But, it is not a common occurrence. The big thing I would tell you to do is make sure that the 2 lines coming off of the master cylinder you plug to keep as much fluid as possible in the reservoir. This will make bleeding the brakes later much easier. The ABS module is easy to reach too as it is behind the right side headlight. Pretty easy to do stuff with.

 

Duncan, when's the last time the brake fluid was properly serviced?

 

she had new fluid and bled a week ago when the wheel bearings were changed, they nicnicked a brake pipe which resulted in fluid leaking drom a rear pipe so i had the pipe replreplaced and new fluid and the breaks bleeding. The leak was bad enough to almost empty the system.
Am i silly for being suspicious that both calipers arw binding ? I thought the rear calipers could be more of an issue but not front !?!?!

 

I am a bit suspicious of the whole "binding" issue. Thermo was "spot on" with his analysis procedure, You should follow his directions clearly and be certain if you even have a problem.
Unlike the old "brake shoes" the master cylinder in the "disc brake" systems allow a little residual pressure on the calipers. The old shoe system needed to be clear of the drum; the disc pads need to lightly drag the disc. It is a clearance and brake pedal thing but since the pads are supposed to drag, a little heat is normal.....Is the car pulling one side or another after driving a couple miles?

 

Unlike the old "brake shoes" the master cylinder in the "disc brake" systems allow a little residual pressure on the calipers. The old shoe system needed to be clear of the drum; the disc pads need to lightly drag the disc. It is a clearance and brake pedal thing but since the pads are supposed to drag, a little heat is normal.

Roncarne , where did you hear that nonsense from ???

 

to: Mastersid.
Maybe you should do your own homework....Tech: More Brake Master Cylinder FAQs - OnAllCylinders
I am done with this thread.....not worth arguing.

 

Ron, the source you stated is referring to the question "So can you use a drum brake master cylinder on a disc brake system?". So, not exactly an apples to apples comparison to what the original poster asked about.

 

Although the link that was provided muddied the waters, Roncarne is correct. It's not nonsense at all.

Disk brake systems unlike drums, have no return springs that pull the friction material (pad/shoe) away from the mating surface (rotor/drum) when the brake pedal is released. This is done deliberately to reduce the pedal travel and reaction time when the brakes are applied.

Some vehicles (ex. all '65-'82 Corvettes and many other fixed caliper designs) have light duty springs located behind the caliper pistons that deliberately push the pads into full time contact with the rotor surface. The trade off is marginally reduced pad life and in theory reduced fuel consumption.

The Op could raise each wheel off the ground after a drive to see if there is unusual rotational resistance. The X-type calipers are a floating design, possibly the garage meant that they are binding on the pins that allow them to move laterally. That's usually an easy fix.

 

Mikey , there are no brake master cylinders that use RESIDUAL LINE PRESSURE for the brake caliper , yes , you are correct about the Corvette caliper " springs " .

Residual line pressure is used in drum brakes to stop the wheel cylinder pistons from retracting all the way back .

Is that not the opposite of what was said in post # 7 ? .

Cheers ,

Sid

 

I think I've muddied the waters. Sorry.

Roncarne is correct that the pads do drag on the rotor surface and that there are no springs to retract the friction material as there are on drum brakes. The article he refers to is incorrect by stating that there is a residual pressure valve to achieve this on disk brake car.s

You are correct about the reason for having a residual pressure valve on drum brake cars.

Group hug?

 

" Fair enough " .