Brake question

[Tim/oh]

Hey all, have a question on brake pedal travel. When I bought my car Aug of last year I knew it had a caliper hanging up. Brakes worked fine but would stick for a few feet after stopping. Turns out left rear and rt front were sticking. So I rebuilt those calipers, all was good then I parked the car for the winter. Got it out a few weeks ago and noticed a very slight drag when leaving a stop light, came home felt the wheels and sure enough the 2 calipers that I didn't rebuild were warmer than the rebuilt ones. I just finished rebuilding those 2 and brakes work great, release great but my pedal is about even with the gas pedal before grabbing. Before I rebuilt these last 2 calipers it was grabbing almost as soon as you pressed it. Bled system with mighty vac, (greased the threads on bleeder valves as not to suck air from around them). Because of lower pedal ended up having someone pump while I bled. Still lower pedal. Originally each caliper had a frozen piston. This may sound funny but the brakes were much firmer with half the pistons frozen. I would imagine if your only moving 4 of the 8 pistons it will take less fluid thus less pedal travel. Just doesn't feel right though. Where should the pedal engage or where do most engage? I read an old thread that said in will take time for seals and pistons to seat properly, I'm a bit skeptical on that. I've never heard or experienced that, but then again this is my first Porsche! Any thoughts or experiences. Thanks Tim

[DRACO A5OG]

Okay, your car is an 86 3.2 so it has a proportioning valve, locate in frunk, check to see if it is leaking/wet.

2nd, test booster. Put your foot on the pedal with a slight pressure to get the pedal to move down about .5-1", Start the car, if the pedal does not drop with that pressure from your foot, booster is shot. Check at the bottom of the booster for wetness as well.

When you did the two man bleed, did you place a block of wood behind the pedal as not to go too deep in the MC and possibly damage the seals?

Last or first would be to check the brake lines are not clogged or not flowing properly, yes, you will need to disconnect the lines and check the flow. But this time, if you have not done so before, place a block of 2x4 behind the pedal

When you wrote "stick" you actually felt it or heard a hum from the pads on the rotors?

[Targalid]

My guess, based on bitter experience, is that Draco is correct about the master cylinder piston seals being abraded from pushing the pedal too far during brake bleeding. There is usually a bunch of corrosion that builds up beyond the usual wear area in the cylinder bore due to age. (Hard to imagine that an 86 is almost 30 years old now.) Easy way to confirm is to step hard on the pedal and see if it slowly goes lower (leaks past the seals) and does it get firmer if you pump it. If so, your MC has abraded leaking seals. The only cure for this is new seals in the master cylinder. Since the rebuild kit costs almost as much as the master cylinder, just get the new master cylinder. But verify you need one first.

[Tim/oh]

Originally Posted by DRACO A5OG

Okay, your car is an 86 3.2 so it has a proportioning valve, locate in frunk, check to see if it is leaking/wet.

2nd, test booster. Put your foot on the pedal with a slight pressure to get the pedal to move down about .5-1", Start the car, if the pedal does not drop with that pressure from your foot, booster is shot. Check at the bottom of the booster for wetness as well.

When you did the two man bleed, did you place a block of wood behind the pedal as not to go too deep in the MC and possibly damage the seals?

Last or first would be to check the brake lines are not clogged or not flowing properly, yes, you will need to disconnect the lines and check the flow. But this time, if you have not done so before, place a block of 2x4 behind the pedal

When you wrote "stick" you actually felt it or heard a hum from the pads on the rotors?

By "sticking" I mean after making a stop and upon letting off the brakes the pads were still making contact with the rotors. Go up a small incline and hit brakes, release and the car would not roll back. Hoses are good. When I rebuilt the 1st 2 calipers last year we did the 2 person pump & bleed, all was well. This time I bled with the mighty vac 1st then noticed the problem. All is dry, no leaks. Just went out to check booster. If I just get in put foot on pedal and start doesn't drop but if I pump the pedal a couple times it will drop on starting. The pedal will not drop with steady pressure like MC is bypassing but I can "pump it up". Wife helped bleed because son was sleeping.....Think I'm gonna bleed 1 more time, with board under pedal. If I can still pump up pedal after that I'm going to assume its the master cylinder.

[cabmandone]

I had the same problem when I rebuilt my calipers. Bleed it again. I used a pressure bleeder that I built that feeds pressurized brake fluid into the reservoir. Started with the passenger side rear then diver rear then passenger front then driver front. I used a different color of fluid than what was in the car (I had blue so I used a gold or clear) and I bled till all the old fluid was out along with all air bubbles.

[Tim/oh]

Originally Posted by cabmando

I had the same problem when I rebuilt my calipers. Bleed it again. I used a pressure bleeder that I built that feeds pressurized brake fluid into the reservoir. Started with the passenger side rear then diver rear then passenger front then driver front. I used a different color of fluid than what was in the car (I had blue so I used a gold or clear) and I bled till all the old fluid was out along with all air bubbles.

That's what my plan is. I'm going to round something up at work tomorrow to pressurize my reservoir. Hopefully that cures my problem. Brakes work great, pedal just lower than I feel it should be. Also feels a little spongy. I've had master cylinders go out and this doesn't act like its the MC. Guessing/hoping air trapped somewhere.

[Bob Kontak]

Originally Posted by Tim/oh

That's what my plan is. I'm going to round something up at work tomorrow to pressurize my reservoir. Hopefully that cures my problem. Brakes work great, pedal just lower than I feel it should be. Also feels a little spongy. I've had master cylinders go out and this doesn't act like its the MC. Guessing/hoping air trapped somewhere.

Where are you in Ohio? I have a motive pressure bleeder. Akron area.

Drive it for a couple of days. Then bleed again.

Those one way bleeders work pretty well for moving fluid volume and may help blowing out a few pesky bubbles. Although, word on the street is one method of bleeding is no better than another.

[DRACO A5OG]

^^^+1 try again, it took me two bleeds before I got all my air bubbles out after caliper rebuild. I used two different methods, reverse and two man.

[cabmandone]

Originally Posted by Tim/oh

That's what my plan is. I'm going to round something up at work tomorrow to pressurize my reservoir. Hopefully that cures my problem. Brakes work great, pedal just lower than I feel it should be. Also feels a little spongy. I've had master cylinders go out and this doesn't act like its the MC. Guessing/hoping air trapped somewhere.

If you're anywhere near Lima Ohio, I'd be glad to help out. If it helps to pinpoint my location, I'm 2 hours from about everything in Ohio but only 10 minutes away from nothing.

[Tim/oh]

Originally Posted by Bob Kontak

Where are you in Ohio? I have a motive pressure bleeder. Akron area.

Drive it for a couple of days. Then bleed again.

Those one way bleeders work pretty well for moving fluid volume and may help blowing out a few pesky bubbles. Although, word on the street is one method of bleeding is no better than another.

I'm in North Canton. I pressure bled them tonight, brakes stop great, pedal still not as high as I'd like. Can still achieve higher pedal by pumping though. I'm going to try to put a few miles on it this week after work, depending on the weather. Might be the pedal was high because of the frozen pistons? We'll see.

[Tim/oh]

Originally Posted by cabmando

If you're anywhere near Lima Ohio, I'd be glad to help out. If it helps to pinpoint my location, I'm 2 hours from about everything in Ohio but only 10 minutes away from nothing.

I'm in North Canton. I did get a ticket in Lima about 30 years ago though.....Thanks for the offer, I pressure bled them tonight, no difference in pedal height....Gonna drive it awhile, bleed them again and see what happens.

[DRACO A5OG]

Since she brakes properly, have you driven her and driven her hard before bleeding again? This will help agitate the bubbles if any and possibly move them down closer to the calipers for the bleed or up the reservoir.

[Tim/oh]

Originally Posted by DRACO A5OG

Since she brakes properly, have you driven her and driven her hard before bleeding again? This will help agitate the bubbles if any and possibly move them down closer to the calipers for the bleed or up the reservoir.

Managed to go up and down my driveway(100ft) a couple of times. It started raining so I put it back in the garage. Don't flame me, I don't drive any of my "older" cars in the rain, never have. Since I was 16 I've always had a "beater" for work and crappy Ohio weather days.

[DRACO A5OG]

LOL, no problem, I totally understand as well as many of other here :-D

When it is safe, go drive her, and driver her hard, especially braking. Maybe best away from traffic, just in case.

[cabmandone]

Another thing you could try is tapping the calipers with a rubber mallet while bleeding if the weather doesn't cooperate.

[CCM911]

I just got done with a caliper rebuild, and my brakes were really mushy. Just felt awful. So I began by removing my brake pads, and having a helper push in the brake until the pistons held in place two pieces of cardboard I place between the pistons and the rotor. Then I eased back the pistons until they just barely let me slip the pads back in. Then we did a brake bleed, only this time "The STIG"(from this board) whomped on the calipers with a big rubber mallet. Sure enough, we burped a monster air bubble from the right rear caliper. ANd then just a few more bubbles from each remaining caliper. A total pain, but now my brakes feel awesome.

Originally Posted by cabmando

Another thing you could try is tapping the calipers with a rubber mallet while bleeding if the weather doesn't cooperate.

[TheSt|G]

Originally Posted by CCM911

Then we did a brake bleed, only this time "The STIG"(from this board) whomped on the calipers with a big rubber mallet. Sure enough, we burped a monster air bubble from the right rear caliper. ANd then just a few more bubbles from each remaining caliper. A total pain, but now my brakes feel awesome.

Rubber mallet or dead blow hammer to the caliper is a good decision any time you bleed the brakes.

[Trackrash]

Also check to make sure your pads do not have excess clearance between them and the rotors. The new seals could be holding the pads slightly back from the rotors.

[Tim/oh]

Never heard the mallet idea before. I'll give that a try. Managed to put about 10 miles on it tonight and will drive it to work tomorrow,about 12 miles. Will bleed them again this weekend with a mallet.