Technical Front brakes binding

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Technical Front brakes binding

adnapTA

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Hello Friends,
My daughters 2009 Panda 1.1 eco front brakes are binding, wheel getting hot, n/s hotter than o/s. New rotors and pads fitted. Bit better but still getting hot. Any advice would be great.

mick(y)
 
Nothing completed. Just a matter of working methodically and checking each part as you reassemble

pads have to be loose in the callipers

no air in the system

Slide pins clean and glide smoothly

pistons push back easily
 
Hi and thanks, checked all except bleeding system. Do you think re-newing brake fluid is good option? had the car a few months 33,000 mls previous owner neglected "rocket" therefore could be original fluid.

thanks Mick(y)
 
Changing the fluid is probably a good idea, but not relevant ot the current problem, so don't get sidetracked.

As said above, the pads need to be free to move in their carriers. The carriers corrode causing the pads to stick, and need cleaning annually.

The calipers generally move on their slide pins fine, but may at older age or higher mileage need new pins.

Caliper psitons can stick. Sometimes pushing them back in and pumping them out again will sort this, sometimes needs a new caliper.

Old brake hoses can delaminate internally, creating 'valves', like in our arteries, that prevent fluid releasing so holding the brakes on. How difficult is it to push the pistons back?

Are you assuming the brakes are binding because of the heat, or because turning the wheel is difficult? If just heat, failing wheel bearings (not common on Panda) could be the cause.

Did you fit the new pads? The wear pattern of the old ones will tell if one or more is wearing more than others, giving a clue to the cause.
 
Brake drums use springs to pull the shoes away from the drum contact surface.

On brake calipers, the hydraulic piston seals provide that return pull. The actual movement is fractions of a mm but enough to distort the square section O-rings so they can pull back when brake pressure is released.

As JRK says make sure the pads are not getting jammed the carrier and make sure the sliding pin is sliding.

You can use the caliper bleed nipple and a heavy duty flat screwdriver to test the piston movement.

(1) With bleed nipple closed, the piston should push back without excessive force from the screwdriver. If you have to really work at it, there is a problem.

(2) Open the bleed nipple and repeat.
(a) If the piston mioves back easily, you can suspect the brake hose has failed internally.
(b) If it is remains hard to move, then suspect the brake piston seal has siezed.
(1) No worries, just be sure the caliper pin slides OK and the pads are not jammed in the carrier.

(2a) Replace both brake hoses and all should be well.
(2b) Get a service exchange caliper.
 
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Brake drums use springs to pull the shoes away from the drum contact surface.

On brake calipers, the hydraulic piston seals provide that return pull. The actual movement is fractions of a mm but enough to distort the square section O-rings so they can pull back when brake pressure is released.

????

Mine drag when testing stationery and so has all the cars I have owned.

After all the disc thickness grows quite a bit when it heats up under braking

As long as there isn't any compressed air in the brake line pushing the piston back out and everything is free to move the pads touching the disc has never been a problem for me
 
Disc brake pads hardly move but they do move a little bit. That tiny bit of retraction is provided by the piston seals.

It's easy to prove with some silicone grease on the piston seal. When its over-lubricated the piston will slip too easily though the seal and there's nothing to pull it back so the brakes bind. I found out the hard way with silicone grease on motorbike brakes. The brakes worked but would not release. A tap with a stick released the pads until next time.

New pistons, new seals (again) and the correct red rubber grease solved the problem. I still have the same pot of grease.

If an old brake with good sliding pins is binding, its either the hose delaminating internally or the piston seal has seized. Post 6 suggests an easy way to diagnose which it is.
 
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The brakes shouldn't be getting hot unless you are on a race track, most probably the caliper carrier (which the pads sit in) are rusty making the pad edges stick, best solution is a round wire brush on a electric drill to clean them up, followed by some copper grease, I have just done mine and they needed a good clean,
 
Regarding your binding brakes, this thread tells you all you need to know.

Thank you for that link to the 500 thread JR. Cleaned up my front calipers last night as part of its pre-MOT service, a wire brush on a drill couldn't remove all the rough rusty build-up on the sliding surfaces on my 16y.o. 1.2.

Which was a bit of a surprise as the other usual rust spots (sump, coolant return pipe and rear axle) weren't too bad on my car, and it had new discs and pads 3 years ago (before we got her).

I had to attack it with a wire brush on the angle grinder to get the sliding surfaces smooth before reassembling with copaslip. Other than that, easy to service, such a simple design:)
 
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Thank you for that link to the 500 thread JR. Cleaned up my front calipers last night as part of its pre-MOT service, a wire brush on a drill couldn't remove all the rough rusty build-up on the sliding surfaces on my 16y.o. 1.2.

Which was a bit of a surprise as the other usual rust spots (sump, coolant return pipe and rear axle) weren't too bad on my car, and it had new discs and pads 3 years ago (before we got her).

I had to attack it with a wire brush on the angle grinder to get the sliding surfaces smooth before reassembling with copaslip. Other than that, easy to service, such a simple design:)

Grinding stone or a dremal type multi tool works well
Probably can get one for a drill as well
 
Thank you for that link to the 500 thread JR. Cleaned up my front calipers last night as part of its pre-MOT service, a wire brush on a drill couldn't remove all the rough rusty build-up on the sliding surfaces on my 16y.o. 1.2.

Which was a bit of a surprise...

Not a surprise to me - the ones pictured in my linked thread were only a few weeks old at the time.

Grinding stone or a dremal type multi tool works well
Probably can get one for a drill as well

Just be careful not to take off any more material than you have to, or the pads will be excessively loose in the reaction frames.

Replacement reaction frames are OEM only, and crazy expensive. Secondhand ones from a breaker will likely be as bad, or worse, so treat them with respect. Parts quality leaves something to be desired, too - on mine, one of the blind holes had been tapped right through the metal at the bottom, potentially letting water in.

Interestingly I've found it necessary to do something broadly similar on every new car I've owned since 1980; goodness knows why these aren't better protected in the factory. At least Fiat's semicircular design makes for easy cleaning with some form of rotary abrasive tool; the more usual square cross section designs used in other marques can be the devil's own to derust thoroughly.

On the 1.2 at least, the front brakes are just about the easiest to work on of any car I've had. Aftermarket discs & pads are cheap as chips, too.
 
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adnapTA

how are you getting on

As its binding on one side it needs sorting ASAP. The near side will react slower. If you brake heavy its liable to swerve to the centre of the road.

jrkitching

has done a brilliant job. I normally just chip off any rust growths with a small screwdriver size chisel and wire brush.

Occasionally there is also a paint drip on the pads that needs to be filled off.


https://www.thepartsalliance.com/delphi-does-not-recommend-the-use-of-copper-grease/
I'm with koalar on this, chip the horrible swollen rust off the pad carrier. Small chisel and gentle hammering, the claws of a claw hammer, air powered needle scaler.
Or a bastard file.

Eye protection when using any of those(-:
 
Not a surprise to me - the ones pictured in my linked thread were only a few weeks old at the time.



Just be careful not to take off any more material than you have to, or the pads will be excessively loose in the reaction frames.

Replacement reaction frames are OEM only, and crazy expensive. Secondhand ones from a breaker will likely be as bad, or worse, so treat them with respect. Parts quality leaves something to be desired, too - on mine, one of the blind holes had been tapped right through the metal at the bottom, potentially letting water in.

Interestingly I've found it necessary to do something broadly similar on every new car I've owned since 1980; goodness knows why these aren't better protected in the factory. At keast Fiat's semicircular design makes for easy cleaning with some form of rotary abrasive tool; the more usual square cross section designs used in other marques can be the devil's own to derust thoroughly.
Just keep the speed down and you should have no issues
That being said the pink grinding stonea are not that aggressive using used to smoothing the surface down or sharpening a blade then material removal
 
While restoring my 1970s Suzuki, I discovered zinc metal spraying. The parts are grit blasted and sprayed with zinc before the base can flash rust. Areas to be kept clean are protected with blast tape. Unlike hot dipping it can be used on parts that cannot be coated 100%. The protection is massive over-kill but the cost is so low who cares. 100HP back axle cost £80 plus paint (which I'd have had to get anyway).

The 'as delivered' finish is quite rough but can be smoothed with wet/dry. I wanted the finish to look OEM so used rattle-can etch primer. On things like brake calipers, epoxy primer would be more suitable.

I have a set of Alfa 146 calipers to try on the 100HP which will be getting the treatment and a full set of new seals.
 
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