usually it's because of non use, creating corrosion, but that's not the case with you I'm sure. I guess the rubber rings go bad as well, I have successfully rebuilt multiple calipers with the kits from IAP
question, why would calipers stick?
i change the fuild every year...
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What kind of brake fluid are you using?
I do hope you are not using American brake fluids that eat thing up. Most Alfa brake systems best use LMA Castrol brake fluid.
I do hope you are not using American brake fluids that eat thing up. Most Alfa brake systems best use LMA Castrol brake fluid.
If you do the rebuild, what are you finding inside of the caliper?? Is it the piston that sticks or the harware?
Not sure where you got that info but it's not true, at least not for for "newer" Alfas. Maybe it makes a difference for the really old stuff, Mongo dunno. Anyway, Bianchi's got an '84 and it's fully compatible with any standard DOT3 or DOT4 fluid.I do hope you are not using American brake fluids that eat thing up. Most Alfa brake systems best use LMA Castrol brake fluid.
LMA is a glycol-based fluid like DOT3 or DOT4. They're all cross-compatible with each other (though DOT3 has a lower boiling point).
All the stuff that forms the other 364 days and doesn't get flushed out as it is not suspended in the fluid but already attached to the piston below the seal.i change the fuild every year...
Crud that doesn't get scraped off when you push the pistons back in to change pads and grows stuff. see above.
Movement at the pad/piston contact area, perhaps extremely low pad wear, has allowed the piston to extend too far and allow the piston to tilt in the bore.
Jealousy, have you put new brakes on another car recently?
Your car is not pleased with you and this is the most inconvenient thing it could come up with, for now.
i use prestone syn. brake fuild, anyway. i am at work for the next 15 mins. a soon as i get home, i am removing the rear calipers and cleaning them/rebilding them
Go ahead, but LMA would be better.
I repeat and reassert that your rubber seals were NOT designed for Prestone brake fluid, especially NOT for Prestone brake fluid. But you apparently like to rebuild your brakes, and if you keep using Prestone you will be able in time to do that easily because you will acquire lots of experience from doing it many many times. So, I suggest you make some observations this rebuild. When you tear your calipers down feel how soft the seals are. Compare them with the new ones in the rebuild kit. Notice how mushy your old one are. That is what makes calipers stick. Prestone EATS Alfa seals. Do you think I have only old cars? Besides, an 84 is not really a new one. I use LMA even in my 164S and my LS. They say insanity comes from repeating the same thing over and over again and wondering why the outcome is never different.
Don't be misled by that Dot 3 or Dot 4 code. That's American standardization of boiling points, not the percentage of natural rubber as compared to synthetic rubber in the seals. I repeat: Prestone EATS Alfa seals.
I repeat and reassert that your rubber seals were NOT designed for Prestone brake fluid, especially NOT for Prestone brake fluid. But you apparently like to rebuild your brakes, and if you keep using Prestone you will be able in time to do that easily because you will acquire lots of experience from doing it many many times. So, I suggest you make some observations this rebuild. When you tear your calipers down feel how soft the seals are. Compare them with the new ones in the rebuild kit. Notice how mushy your old one are. That is what makes calipers stick. Prestone EATS Alfa seals. Do you think I have only old cars? Besides, an 84 is not really a new one. I use LMA even in my 164S and my LS. They say insanity comes from repeating the same thing over and over again and wondering why the outcome is never different.
Don't be misled by that Dot 3 or Dot 4 code. That's American standardization of boiling points, not the percentage of natural rubber as compared to synthetic rubber in the seals. I repeat: Prestone EATS Alfa seals.
There's your problem. Flush out the synthetic fluid.i use prestone syn. brake fuild, anyway. i am at work for the next 15 mins. a soon as i get home, i am removing the rear calipers and cleaning them/rebilding them
bs
i's prestone dot 4 synthetic fuild, not silicone fuild.... and i got one caliper done before it got dark.... the seals in the caliper were just fine.. not soft at all, nice and springy...
and what is that center pin for in the caliper? i remeber the fronts don't have that pin..i looked.. i am not useing ate calipers in the front anymore, just my 4 piston mazda rx7 aluimiun caliper..
86 spider.. the inside of the caliper where ok.. just a little rust below the dust rubber.. got some 1000 wet / dry soaked it in brake fluid, ckeaned it up.pistons where ok.. strange.. but that was only the pass. side, will do the drivers side in the morning, before i go to work.. after i rebuilt the pass. side.. checked it out.. pistons were moving.lots of brake pad left..
twoliterlover, not sure what to tell you other than you're wrong. Alfa brake parts can handle standard brake fluids: check your owner's manual. I think you're thinking of the old British Girling natural rubber crap that used mineral oil or somesuch.
LMA is good stuff but not a requirement. For the record I haven't had a failed rubber part in the Spider brake system in ten years and I'm not particularly choosy about my DOT4 brand, I just flush it every two years.
Brian: "synthetic" is just a marketing term when it comes to some DOT 4s. You're thinking of DOT 5 silicone, which should definitely be avoided.
LMA is good stuff but not a requirement. For the record I haven't had a failed rubber part in the Spider brake system in ten years and I'm not particularly choosy about my DOT4 brand, I just flush it every two years.
Brian: "synthetic" is just a marketing term when it comes to some DOT 4s. You're thinking of DOT 5 silicone, which should definitely be avoided.
I'm telling you, man...if both sides started dragging at the same time, it's unlikely to be the calipers: both calipers wouldn't have gone bad at the same time. Look at things that would affect both sides in the rear: the hose or the proportioning valve for starters.86 spider.. the inside of the caliper where ok.. just a little rust below the dust rubber.. got some 1000 wet / dry soaked it in brake fluid, ckeaned it up.pistons where ok.. strange.. but that was only the pass. side, will do the drivers side in the morning, before i go to work.. after i rebuilt the pass. side.. checked it out.. pistons were moving.lots of brake pad left..
Frequent changes/flushes with fresh brake fluid is a good idea. It will help slow down but won't prevent the need for eventual service.
A little understanding of how disc brake calipers work might help. Note there are no springs to retract the pistons. The square cut O-rings (aka seals) are responsible for that function. When you apply the brakes the piston is moved out and the O-rings distort slightly. When you release the brakes they are supposed to pull the piston back a tiny amount.
Note that the piston slides in the O-rings. The seals do not slide in the bores like the pistons/rings in the engine. The critical components in the brake calipers are the grooves the O-rings fit in to, the finish on the outside of the pistons & the O-rings themselves. When rebuilding the calipers it is important that the grooves where the O-rings reside are clean. It is common for gunk to build up in the grooves which then makes the O-rings grip the pistons too tightly. This wears the O-rings prematurely and messes with their ability to distort/retract the pistons. As the brakes drag the resultant heat accellerates the degradation of the brake fluid & encourages the build up of the crud in the calipers. When rebuilding the calipers carefully clean the grooves being very careful not gouge them. I use a popsicle stick whittled to fit the groove as a scraper. It will get the crud out without scratching the metal.
If the surface of the pistons has degraded (corrosion & pits) that will also wear the seals prematurely again leading to dragging brakes & possibly fluid leaks. Replacing the pistons is usually the only option in that case.
Another part of the hydraulic system that can cause dragging brakes is a flex hose with an internal failure such that a flap of rubber/fabric acts like a one-way valve or severe restriction to fluid flow. Applying the brakes is no problem as pedal pressure overcomes the restriction. But they don't release properly due to the restriction. An easy way to check if that is the problem is to jack up the car, have your trusted assistant apply then release the brakes. If the wheel won't then turn easily, loosen the bleed screw. If a spurt of fluid comes out & the wheel then turns easily suspect a faulty flex hose.
A little understanding of how disc brake calipers work might help. Note there are no springs to retract the pistons. The square cut O-rings (aka seals) are responsible for that function. When you apply the brakes the piston is moved out and the O-rings distort slightly. When you release the brakes they are supposed to pull the piston back a tiny amount.
Note that the piston slides in the O-rings. The seals do not slide in the bores like the pistons/rings in the engine. The critical components in the brake calipers are the grooves the O-rings fit in to, the finish on the outside of the pistons & the O-rings themselves. When rebuilding the calipers it is important that the grooves where the O-rings reside are clean. It is common for gunk to build up in the grooves which then makes the O-rings grip the pistons too tightly. This wears the O-rings prematurely and messes with their ability to distort/retract the pistons. As the brakes drag the resultant heat accellerates the degradation of the brake fluid & encourages the build up of the crud in the calipers. When rebuilding the calipers carefully clean the grooves being very careful not gouge them. I use a popsicle stick whittled to fit the groove as a scraper. It will get the crud out without scratching the metal.
If the surface of the pistons has degraded (corrosion & pits) that will also wear the seals prematurely again leading to dragging brakes & possibly fluid leaks. Replacing the pistons is usually the only option in that case.
Another part of the hydraulic system that can cause dragging brakes is a flex hose with an internal failure such that a flap of rubber/fabric acts like a one-way valve or severe restriction to fluid flow. Applying the brakes is no problem as pedal pressure overcomes the restriction. But they don't release properly due to the restriction. An easy way to check if that is the problem is to jack up the car, have your trusted assistant apply then release the brakes. If the wheel won't then turn easily, loosen the bleed screw. If a spurt of fluid comes out & the wheel then turns easily suspect a faulty flex hose.
Yes,, **** marketeers! Should have named one of them something that didn't start with an S!twoliterlover, not sure what to tell you other than you're wrong. Alfa brake parts can handle standard brake fluids: check your owner's manual. I think you're thinking of the old British Girling natural rubber crap that used mineral oil or somesuch.
LMA is good stuff but not a requirement. For the record I haven't had a failed rubber part in the Spider brake system in ten years and I'm not particularly choosy about my DOT4 brand, I just flush it every two years.
Brian: "synthetic" is just a marketing term when it comes to some DOT 4s. You're thinking of DOT 5 silicone, which should definitely be avoided.
bs
Eric, very nice summary. Another thing to look for is whether the comp ports in the master cylinder are restricted. If something is holding the brake pedal down, like a poorly adjusted lamp switch, then the MC piston won't fully return home and a seal can cover this small port that normally allows fluid to return to the reservoir. If you loosen the MC from the booster and a previously stuck caliper is then free, that's were the problem lies.Another part of the hydraulic system that can cause dragging brakes is a flex hose with an internal failure such that a flap of rubber/fabric acts like a one-way valve or severe restriction to fluid flow.
update.. the pass rear claiper inside was stuck..hard,outboard piston came out... pistons where ok. just a cleaning did the work.. soaked them over night in carb cleaner.. the paint thinner to wash out, blow dry, toothbrush to clean the grove.. drivers rear, i little stuck, same as above cleaning... work great now.. thank for the help.. i put a little die-electric grease in the dustboots to keep the mosture out..
They sell neutral grease for calipers, BTW, supposed not to eat rubber
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