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#1
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Piston stuck in caliper.
Installed new front disc brake pads on my 1971 FB. New pads were thicker than the old so had to compress piston in to caliper in order to get caliper on to the rotor. (Calipers are new with only a few hundred miles on them.) Now when I apply the brakes the caliper on the passenger side will not extend. The driver side caliper does extend properly. Also, before i realized that the caliper was stuck I tried to bleed the front brakes and could not get any fluid to spit out. Could there be an issue with the proportioning valve not being centered? Every last component in the brake system is new and the valve, booster and M/C are from The Right Stuff. Any ideas?
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1970 T/A |
#2
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If it is giving you trouble now replace it before you have trouble on the road. There certainly aren't expensive.
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#3
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Just wondering if that caliper was working before you changed pads ?
If the car is new to you, that line may have been blocked of for some reason. I've blocked off the line to one wheel before, usually because of a leak. I sometimes used a small nail at the end of the line. May be crude, but worked. |
#4
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If one side works and one doesn't, it's s not related to a proportioning valve.
Start with loosening the connections in the line to see where the obstruction is. That way you can pinpoint the problem, as opposed to guessing and replacing parts unnecessarily. |
#5
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Not certain if the one piston was working before I changed the pads. I spoke to the Tech, at The Right Stuff where all of the brake parts were sourced and was told the Prop valve was "off center". They sent me directions on how to correct this but I must wait for a helper this Saturday as it is a two man procedure. Stay tuned.
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1970 T/A |
#6
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Quote:
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1966 Pontiac GTO (restoration thread) 1998 BMW 328is (track rat) 2023 Subaru Crosstrek Limited (daily) View my photos: Caught in the Wild |
#7
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Brake hose ?
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#8
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I am unable to get any fluid what so ever out of either of the front calipers. The rear wheel cylinders do have excellent flow. Every last component in the brake system is new including the hoses but I will look at them again closely. I would not think that both front hoses have collapsed internally. Tech support assured me the problem is with the Prop. valve. We will find out Saturday.... Thanks again for the input everyone. I will report back.
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1970 T/A |
#9
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My helper is home from college and we were able to reset the Prop piston per The Right Stuff instructions. I now am able to bleed the brakes at all 4 corners.
The reason why i replaced the front pads in the first place is because the front brakes never grabbed hard and I can not lock up the brakes. I did thoroughly bleed the brakes using the correct procedure and took it on the test ride. Result is still the same. Just feels like the front brakes are not working completely and still can not lock up the brakes. Again, every last brake component is new. Very frustrating.
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1970 T/A |
#10
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You need to stop guessing and measure the pressure at the brake calipers.
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#11
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Sounds to me like you still have air in there. This may sound silly but when I bleed brakes I wont stop if I get all fluid out of the lines or see the caliper flexing. I keep going until I get about 8 oz out of each corner. Then I will drive it around 20 miles or so and come back and do it again. And still get some air out after that.
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" Is wearing a helmet illegal" Mike Kerr 1-29-09 |
#12
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You may be correct about the air in the lines. I have bleed the system 3-4 times now and each time I do, this is what I experience: Helper pumps the brake pedal 3-4 times and then holds, I open the bleeder at the right rear and get a bunch of air bubbles. On the second attempt we use the same procedure and I get 4-5 air bubbles. 3rd attempt I typically get one or no air bubbles. I do use a clear tube on the bleeder that is fully submerged in a catch-jar of brake fluid. I then go to the left rear, R.F. and then L.F. When done, I have a good firm pedal but the brakes still don't stop very well. When I then start the brake bleeding process all over again the next day or the next week, I get more air bubbles as described above. There are no leaks anywhere and again, every last component is new. (Yes I did bench bleed the M/C). Maybe I can find a shop that has a pro-quality pressure bleeding system? I am stumped. Thanks all.
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1970 T/A |
#13
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I believe I found the problem: When I pulled the M/C away from the booster, there was brake fluid in the recess of the booster where the push rod exits. The M/C was not overfilled and there is a new gasket seal on the M/C lid. The Right Stuff Detailing is sending me a new M/C. Hope this does the trick. I will report back.
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1970 T/A |
#14
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for bleeding procedure, i have always simply had the helper push the pedal down firmly after i crack the bleeder open, then i close the bleeder while pedal is still down & they let up the pedal. i do that 3 or 4 times then check/refill the resevoir. never heard of pumping the pedal 3 or 4 times & holding before opening the bleeder. but hopefully the end result is the same if it gets the air out of the lines.
& did/will you bench bleed the master properly before installing it? |
#15
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Yes I always bench bleed the M/C before install. I will get to this on the weekend and hope this does it. Thanks for the input.
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1970 T/A |
#16
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Update but same old issue.
Received the replacement M/C and reinstalled after thoroughly bench bleeding per instructions. Bled entire system and still have a soft pedal and can not lock up the brakes. Braking is less than adequate and not safe. Bled all 4 positions again and still have the same result. What is strange is that I bleed each position until I get zero air bubbles. But if I test drive the car and bleed again, I get many many air bubbles from all 4 positions. There are no leaks and no loss of fluid. What should I try next? Thanks.
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1970 T/A |
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