New Rotors and Pads - Newbie Question and Advice Needed

[cgoguen235]

For my 1987 Carerra 3.2 Cabriolet.
I just completed replacing my rear rotors and pads (including brake sensors). Other than a tight fit to get the pads back in, it was pretty straightforward based on the instructions I have received from the form here.

My questions are as follows:
1. I noticed that my brake pad warning light on the dash is still illuminated. Any idea why this might have happened?
2. When I pulled the car out of the garage to "bed the brakes" it felt as if the brakes were engaged slightly as I met resistance when I put the car into reverse. Yes, the emergency brake was off at the time. Is this normal during the break in period?
3. After I spent a little time "bedding the brakes" I returned to the garage. I noticed that the wheels/brakes were emitting a lot of heat. Is this something I should expect as well?
4. Last question – I'm assuming that since my brakes performed fine, I should feel confident that the brakes are in good shape and I should be comfortable with their performance. (meeting I didn't royally screw up anything)

Thank you all for your help in advance. I am very new to this and am learning as I go along

[BFT3.2]

When you installed the new pads the fit should not of been "tight". Did you push the pistons back in to the caliper before you installed the new pads? If not then your pads are probably dragging on the rotors and that should not be happening.

[ganun]

1. front brake pads worn or break in the sensor wire somewhere or dirty sensor plug connector.
2. no,
3. yes, bedding in involves several stops with increasing pedal force but also a cooling period in between, nevertheless the wheels and brakes are expected to be hot
4. when pushing back the pistons, they should smoothly push back all the way flush with the face of the caliper. if some were harder (much harder) to push back than others or you couldn't bottom them out then a caliper rebuild is in order. pads should slip in NP. And the brake pedal should be pumped to make sure the pads are seated against the rotor before driving the car, otherwise a pedal to the floor moment at the corner stop sign.

[85911]

Normal driving should not generate heat in the brakes. If you used them hard in the process to "bed the brakes", then heat will be noticeable. Try driving it normaly for awhile and if the heat is still there, I agree with BFT3.2 above.

[cgoguen235]

Thanks - yes, i did use a tool to try and push in the pistons but the only way I could get them in was to loosen the caliper from the hub and put in the pads. Then I tightened the caliper back. How does a caliper rebuild work?

[BFT3.2]

But the question still remains.. Did you push the pistons all the way back in to the calipers, or only a little? When you say "them" it seems your referring to the pads? If so, you should not have to loosen or remove the caliper to install the pads. They should just drop in after the pistons have been pushed all the way in, especially with new rotors that don't have a rusty lip to them.

[cgoguen235]

BFT3.2 - thanks for the follow-up question. I tried to push the pistons back with an X spreader tool but pistons didn't seem to move at all. This happened on both sides. From the comments, possibt I need to rebuild the calipers. Is that something a newbie can do from following directions? Would hate to have to brig to my local porsche mechanic.

I agree that the pads should slip in and was concerned at the problems I have had.

[BFT3.2]

I can't 100% remember right this second (Im sure others will know) but you may have to remove the brake fluid reservoir cap to relieve the pressure being created by pushing the pistons in. Or I could totally be wrong as the vent tube in the reservoir should bleed the pressure? I know my fronts gave me a bit of a hard time going back in but once they broke free they retracted fine. The easiest time to push the pistons back in is when there is no rotor installed or the calipers are removed, which obviously lead to bleeding the brakes. Not sure if you've done that before. If they need new seals installed, for the price of having a mechanic remove, rebuild, reinstall, bleed etc. you might be better off removing them yourself and buying a reconditioned pair from PMB that are "as good as new" for $300 after the $100 core refund. You or someone qualified would still have to bleed the system after installing.
PMB - Mid 911 Brakes

Yes you could do it yourself but it may be something you want to leave to someone else depending on experience etc.

[RSTarga]

I would second the advice above, send them to PMB. If this was the first time you've changed pads, and are having these troubles, you would be better going to a pro rebuilder on something as important as brakes.
You were lucky your brakes didn't catch fire. There should have been no pressure on the disk, without applying force on the pedal.
Are you certain your brake hoses have not collapsed? Just another possibility.

[911pcars]

The brake system is only pressurized when the master cylinder piston moves forward (brake applied). When brake pedal is at rest, fluid is free to flow from reservoir to caliper as needed.

I use insert worn pads (or equivalent) then use a pry bar between the rotor and spacer to slowly and evenly retract each piston. You should not have to remove the caliper to install new pads. Observe the reservoir as the fluid level approaches the overflow level.

[Jdub]

Bedding the new pads and rotors involves driving the car for as long as it takes to cool the pads and rotors following your sequence of stops. That is, the collective heat should be dissipated so that when you finally park the car overly hot pads are not contacting only one section of the rotor, which, if hot enough, causes rotor warp.

Last time I did this was on a Sunday morning with very little traffic. Sequence of bedding by braking, then a return home by a longish road with no stops to allow cooling air to circulate.

[cgoguen235]

Folks - thanks for your advice. BFT3.2 - I did take off the reservoir cap when pushing back without any luck moving hte piston. I think I will try PMB rather than try it myself. RSTarga - I think my brake hoses are ok but plan on replacing with the rebuilt rotors.

Last question - how much damage do you think I did to the rotor/pads on my 20 minute 'drive'

Thakns everyone

[Corvus Corvax]

Originally Posted by cgoguen235

Folks - thanks for your advice. BFT3.2 - I did take off the reservoir cap when pushing back without any luck moving hte piston. I think I will try PMB rather than try it myself. RSTarga - I think my brake hoses are ok but plan on replacing with the rebuilt rotors.

Last question - how much damage do you think I did to the rotor/pads on my 20 minute 'drive'

Thakns everyone

Not to repeat what others have said, but to offer my technique. When I push the pistons back, I keep the reservoir cap firmly in place, keep the overflow hose crimped, and open that caliper's bleed screw. I don't want that fluid going back into the system, so I get rid of it. When the pistons are flush, I tighten the bleed screw again. To be fair, when I replace pads, I also replace the rotor, because rotors are cheap, and because I'm lazy. I'm sorry I didn't answer any of your questions, and good luck with the issues.

[cgoguen235]

Thanks all - I received my 'rebuilt' calipers from PMB (quick service/shipping). Pads fit great - definitely was a seized set of calipers. I am going to post another thead with the following question but I will ask here anyways:

I am not touching the front brakes - just calipers/pads/rotors on rear. I plan to do the front at the end of the summer. My question is as follows: Do I need to bleed ALL the brake fluid from the brake system (front and back) or do I reattach calipers/pads/lines/sensor/etc and add fluid to reservior (all the fluid in rear came our when I removed calipers) and pump brakes to pressurize the lines. I plan to do a full bleed/replace when I do the front in late August. Does this question make sense?

[Cairo94507]

I am not sure how old your brake fluid is, but I know brake fluid absorbs water over time and that is why it is recommended it be flushed every few years. Once you have replaced your brake lines and have the new front calipers/rotors/pads installed, I would completely flush the whole system, relaxing your existing brake fluid. Your already bleeding the system, just flush it in the process.

BTW, so glad to see you went with PMB - they are the best and Eric is just a great person. I did all of my brake restoration through them.

[Drisump]

Originally Posted by cgoguen235

Thanks all - I received my 'rebuilt' calipers from PMB (quick service/shipping). Pads fit great - definitely was a seized set of calipers. I am going to post another thead with the following question but I will ask here anyways:

I am not touching the front brakes - just calipers/pads/rotors on rear. I plan to do the front at the end of the summer. My question is as follows: Do I need to bleed ALL the brake fluid from the brake system (front and back) or do I reattach calipers/pads/lines/sensor/etc and add fluid to reservior (all the fluid in rear came our when I removed calipers) and pump brakes to pressurize the lines. I plan to do a full bleed/replace when I do the front in late August. Does this question make sense?

You will likely find it necessary to bleed the entire system....air has a nasty way of getting everywhere once a good portion of one circuit is emptied. Personally, I use Pentosin super dot 4 which can't be described as cheap.....so I would do all of the brake work at one time, otherwise you will likely be bleeding twice within a couple of months. If the brake light is still on, what did you do around sensor wire replacement, also what makes you think the light is being generated from the rear.....as opposed to an indication of wear in the fronts? In general observation of my two cars, 911's do seem to go through pads quite a bit faster in the front. Just a little tip, I find it useful when bleeding (unless pressured) removal of the strainer in the reservoir is a good idea. The strainer slows down the supply of fresh brake fluid to the MC sufficiently to introduce air into the system...do'h! Cheers

[jwill911]

My 2 cents on the subject.

If you're removing the calipers press and hold the brake peddle, you can block it with a piece of wood short 2x4 about 16" and something soft to put on the front of the seat and use the electric seat to push the peddle. This will stop all the fluid from draining out of the system. Ask my how I know. You're going to want to bleed/flush it anyway but you don't want to make it a bigger job than necessary. It is a PITA to get all the air out of the system otherwise.

I don't understand the purchase of rebuilt calipers for $300, rebuilt calipers are just cleaned with a new "O" ring. The piston doesn't wear. But I'm an incurable do-it-yourselfer. You'll want a 20 degree tool to position the caliper piston in proper rotational orientation. You can make one pretty easy, I believe manual has a picture of it.

[RSTarga]

Do your self a favor and buy a pressure bleeder from our host. It will reduce the time spent on a brake bleed to almost nothing. Yes you will have to bleed the whole system, starting LR, RR. RF,LF.
Always start with the caliper furthest from the reservoir.
I don't put fluid in the power bleeder, just keep anele on your reservoir after each wheel. Make sure to clamp off your overflow hose.

[CCM911]

RSTarga, don't you mean start with the RR. Then LR, RF, LF?

[911pcars]

I think a pressure bleeder is overkill and sometimes messy. That is, it consumes (wastes) a lot of good brake fluid. "Good" often means expensive. There are less aggressive methods of bleeding the system. Gravity bleeding takes more time, but it often does a better/more complete job of ridding air bubbles and uses less fluid (I have bled an empty brake system with one liter of BF, about the capacity of the system).

Sherwood