Brake job today, took 6 hours, uggg

[James Brown]

Had a sticky rear caliper so finally decided to fix it. Rears first, Looked ok took quite some time (and air pressure) to pop them out. Lots of rust and crap but cleaned up well. New parts, pads, fluid. Don't even think they were working all that much. Fronts were better but lots of rust and torn dust seals. Same for them, parts pads fluid. Power bleed to the rescue. That makes for quick bleeding. Hoses are less than 2 years old so kept them. new fluid (1.5 qts) and all air gone. Peddle feels softer but experiencing the all too common "soft pedal after rebuild". car stops great, kind of pulls down instead of nose diving and now can lock all 4 up. just have to wait for the pistons to creep out closer to the rotors. Will update in a few days. Also, now i can push the car with one hand! rolls like it should.
Cost, around $125 for pads, rebuild kits, fluid (thanks Wayne).
Missed the F1 race but feel better about the brakes now!

[sc_rufctr]

Well done...

Any pictures of the callipers before rebuilding for reference?

[James Brown]

No but they look like callipers, nothing out of the ordinary so I didn't take any pics. They look good now!

[pete3799]

Just got done doing the rears on mine.They also put up a hell of a fight popping them out.
Don't think they were doing much braking.
Insides didn't look too good but i cleaned them up as best i could and put them back on.
Fronts are next. Hope they look better.

[T77911S]

the pedal may be softer due to all pistons working now. if the pistons are frozen, the pedal has something solid or non moving to push against so it is harder. if you push the pedal, and it starts to give whille holding it, you still have a problem. if you can pump it and it gets harder, it likley has air in it.

when i did the 911 a few years ago, i found one piston on each caliper stuck, what an amazing difference in the breaks. ( the car sat a lot with the PO)

i just did a friends volvo last week. i spent 4 hours on the fronts, should have taken about 15-20 minutes per wheel. his pedal was rock hard when i started, much softer now, but good, after i finished. i only got to the fronts. i was in such a bad mood that it took me so long and that i did not get anything of mine done that day, i did not want to even look at the rear.

my thoughts on this after doing his breaks. dont baby the breaks. he drives like an old lady, including wrecks, so he never puts enoough pressure on the breaks to make all 4 pistons on each caliper move to keep them working. after a while, of only using 1 or 2 pistons to stop the car, the others get stuck, then wwhen he needs them, they do not work. BTW, one of his pads was worn out, the other only about 1/4 used. the volvo breaks were kinda neat. they had 4 pistons, one bleeder valve for each set of pistons, 1 bleeder at the top of the caliper, for a total 3, and 2, yes 2 brake lines to each caliper.

on my volvo, i can pull out the pads, sqeeze out the pistons with these large set of pliers, pop in new pads, let some fluid drain out, or maybe one or two pumps, and i am done. 20 minutes, tops. all because i USE my breaks. i may go 5 or maybe 10k less miles, but my breaks work when i need em.

i dont think the BMW i just bought was driven very hard either. the break pedal is very hard and the car does not stop. i have been getting on the breaks pretty hard every now and then and they are starting to get better. i have not had time to pull the front wheels and check them. i have also been hitting the rev limiter quite a bit, its even running better.

cars are meant to be driven. if you dont drive them hard every now and then, it will cost you more down the road. i have had more go wrong with a car that sits than one that is driven daily.

[Superman]

I prefer a high, hard pedal so here's what I do: Remove each pad, one at a time, and blip the brake pedal. Enough so that you need to use a small hammer to wedge the pads back in. If the pads come with little sheet metal shims, don't use them. I just did this last week. In fact, my pads came with a black piece of tape on the back side (presumably for anti-squeal). The hammer method wasn't going to work with that tape, so I removed the tape. The hammer method gets you a nice, firm, low-travel pedal.

And finally, be sure to "bed" the brakes. Seriously. If you don't, then some day you will do a panick stop and the HOT pads will come to rest against the rotors at one location, and temper the rotor there. You will end up with pulsing brakes. The bedding process simply involves HARD braking, but not to a stop. Go find a stretch of road without water, traffic or police officers. Accelerate to 100 mph, and brake hard down to 20 or so. Get back up to cruising speed. Repeat. Get those pads and rotors HOT, but without coming to a stop.

[vash]

Originally Posted by Superman

I prefer a high, hard pedal so here's what I do: Remove each pad, one at a time, and blip the brake pedal. Enough so that you need to use a small hammer to wedge the pads back in. If the pads come with little sheet metal shims, don't use them. I just did this last week. In fact, my pads came with a black piece of tape on the back side (presumably for anti-squeal). The hammer method wasn't going to work with that tape, so I removed the tape. The hammer method gets you a nice, firm, low-travel pedal.

.

never understood this ^. earlyS talked about this alot, and plenty of guys here do this. BUT: dont our brakes, i mean wont our brakes (any brakes) "ratchet" out to this same position the very first stop? i mean using a hammer to tap in the pads, is alot less force than the fluid pushing the pads out to stop the car. then there really is nothing, no mechanism to pull the pads back in to some "looser" than "tapping the pads in with a hammer" position. earlyS knew more about any car than i ever will, hard to question him. but i cant get my mind to wrap around this. explain?

[pete3799]

I'm with vash.
That hammer them in seems a little hard to swallow.

[Superman]

Originally Posted by vash

never understood this ^. earlyS talked about this alot, and plenty of guys here do this. BUT: dont our brakes, i mean wont our brakes (any brakes) "ratchet" out to this same position the very first stop?

No, they won't. This is why Warren, and I, use the hammer method (I'm sure he's still wrenching on 911's......up there.....). The o-ring inside the bore has a square cross-section and experiences slight friction against the piston. So....when you use the brakes, the piston moves outward and the o-ring deflects. When you release the brakes, the o-ring maintains just enough flex to draw the piston back into the bore, away from the rotor.

Some have said that, over time, the o-ring relaxes and the pistons stop retracting into the bore due to the o-ring deflection. Don't count on it. I've driven hundreds of miles, only to give up and use the hammer method.

I'm not talking about a sledge hammer here. Just a tight enough fit so that tapping is necessary.

[T77911S]

Originally Posted by vash

never understood this ^. earlyS talked about this alot, and plenty of guys here do this. BUT: dont our brakes, i mean wont our brakes (any brakes) "ratchet" out to this same position the very first stop? i mean using a hammer to tap in the pads, is alot less force than the fluid pushing the pads out to stop the car. then there really is nothing, no mechanism to pull the pads back in to some "looser" than "tapping the pads in with a hammer" position. earlyS knew more about any car than i ever will, hard to question him. but i cant get my mind to wrap around this. explain?

never heard of this either. i do stomp the breaks quite hard after new pads. i usually do it before i put the wheels back on, then do a test drive and stomp them again to make sure it stops ok. if the calipers and seals are in good shape i would not think this would make a difference. besides, if the pistons are pushed all the way in, then the pads are put in and then the pedal pressed, wouldnt that leave the piston in an outword, (inword actually) position since the piston has to move in to meet the pads?

[James Brown]

Have read Warren's posts and I do understand the jest of it. When installing new brakes, there is a good gap between the pads and the rotor. Stepping on the pedal pushes the pads out and, contacts the rotor stopping the car. Then, you let off the pedal, the M/C retracts PULLING the pads back to there starting point. So in fact there is no air in the system but less fluid in there to keep the pedal firm and the pads close to the rotors. Warren's fix is a good one (taking the slack out of the brake pads) buy extending the pistons, with fluid, then putting the pads back in with zero clearance. This will also happen normally over time a little at a time.

[Superman]

James.....if it happens at all, it takes a LONG time. I rebuilt my brakes when I assembled my current car, probably a thousand miles ago. I finally got tired of the pedal travel, so I did the Warren upgrade. It's not so much the MC retracting. It's the deflection of the rubber seal between the bore and the slave cylinder.

And again.....don't forget the bedding procedure. There is a thread, right now, on this forum, that discusses pulsing brakes. This is not caused by a "warped" rotor. It is caused by a rotor that is hardened in one spot.

[James Brown]

Update: went out for a drive and did some hard braking to set the pads. The pedal now feels great, good modulation between locked and released in a hard stop. Pedal now moves about a inch farther than before engagement. Nice and firm. I would like to try the Warren method soon but for now they feel great Much more stopping power than before. On a side note, the car rolls so easily now I can start off with about 1100 rpm and smoothly accelerate from there. Now I have to re-adjust how I drive the car! Should also get better fuel mileage. And for S+G I'll re bled the system (drove down some bumpy roads to help dislodge some air bubbles, if any were in there).

Superman, this is what I have a hard time getting my head around, if the square O ring deflects how did I get the piston into the bore in the first place? Slides in fine and, there is only a few thousandths of O ring protruding from the seat to contact the piston-not much O ring material to pull the piston back. These pistons should work just like the seals in any hydrolic actuating cylinder. My guess is that when the MC retracts it pulls the pistons back (negative pressure) fluids are not compressible or expandable, and now that they work (go in and out) it is purely physics. If I could inject more fluid into the system to extend the pistons, I bet that would work!

[Flieger]

Remember, the reservoir is vented so the master cylinder can just draw down the fluid level instead of pulling negative pressure on the pistons.

[James Brown]

Understand that but when the pistons in the MC are retracting, when you lift off the pedal, the system is closed till the MC is back all the way. Then it is open to atmosphere. Pedal feel is getting better and fluid is dropping in the MC so maybe this will work it self out. Brakes feel real good. Brake feel prior was real hard but only 4-5 pistons were moving, now all 8 are working.

[911pcars]

With the brake pedal released (not depressed), the master cylinder pistons have no affect on the position of the caliper pistons. The MC pistons retract because the pedal, acting on the MC pistons, no longer exerts force against the fluid column. When MC fluid pressure is released, the individual caliper pistons retract slightly due to the piston seals. The slight reversal of fluid flow and the primary and secondary MC springs causes their respective MC pistons to return to the ready position.

Something like that.

Sherwood

[pete3799]

Originally Posted by 911pcars

With the brake pedal released (not depressed), the master cylinder pistons have no affect on the position of the caliper pistons. The MC pistons retract because the pedal, acting on the MC pistons, no longer exerts force against the fluid column. When MC fluid pressure is released, the individual caliper pistons retract slightly due to the piston seals. The slight reversal of fluid flow and the primary and secondary MC springs causes their respective MC pistons to return to the ready position.

Something like that.

Sherwood

So are you saying the Early S Man procedure is not effective?
I don't see how you could hammer a pad in with out it pushing the piston back
as much as it would go back on it's own after you release the pedal.

[James Brown]

I think what Warren means is this allows more fluid in the total system allowing the piston and pad to be tight aganst the rotor making a higher firmer pedal.

[T77911S]

i think what they are saying is that when the piston moves in, the seal is at the bottom of the piston. then, the piston is pushed back just a little so the seal is at the top edge of the groove in the piston ( is a better way to put it). this keeps the piston closer to the pad and the pad closer to the rotor thus lees travel distance for the pedal.

the things i see wrong with this. if the pad is closer, even touching, the rotor more, this could cause cooling issues.
as the pads wear, the piston will move in more, then the seal will be at the bottom of the groove unless you keep pulling the pads and doing this all over again.

i dont see how this will make the pedal more firm. it "could" make it have a higher pedal, for a while. a firm pedal comes from having good seals, in the calipers and MC and no air in the line and no rubber break lines.

when i was doing those volov breaks from hell, i had one of the pistons out almost enough to get the pad in. i started to tap it in, out of frustration, as was said but i stopped. even though it was going in, and not a lot of tapping was needed, i started to think about damamge to either the piston, the pad or mainly the rubber boot or seal around the piston. i could not be sure the pad was not tearing that seal, so i stopped and worked the piston out some more.

[James Brown]

Yeah T77911S, I don't like the hammer method. Here's another thought. When the MC springs back, ports open in the MC piston and allows fluid to back fill the calipers as material is worn off during normal braking. Assuming there is no air in the system, the pedal should be at the top and hard all the time. Not saying my MC is bad and I didn't touch it but might get a rebuild kit for it.