Stuck brake pistons???????????? - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 11 (permalink) Old 06-14-2019, 12:11 PM Thread Starter
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Stuck brake pistons????????????

Hello All:

Every time I check my brakes, the pistons are stuck making tire rotation difficult. I was taught that the pistons must be able to move freely. I have three cars that exhibit these symptoms.

How can I avoid this problem? Must the pistons be removed, cleaned and new seals installed at regular intervals? Where is the best source for a seal kit and new pistons. Are parts stores a god source or should I purchase genuine Datsun-Nissan parts? How much air pressure ,PSI, is needed to blow the pistons from their bores? In the past, I could not remove the pistons and purchased a rebuilt caliper assembly with pistons installed.

Any suggestions as how I may prevent stuck pistons in the future? I dread repairing 12 brake pistons!!!!!!!!!!!!!!!!

Tia,

leomat
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post #2 of 11 (permalink) Old 06-15-2019, 02:20 AM
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Rather odd that three cars would be doing that. You say it's difficult to rotate the tire but not that it's really hard to rotate. Are the pad-notch, slide/pin surfaces clean and rust free? And lubricated it the pin goes thru a sleeve?

zippityzda
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post #3 of 11 (permalink) Old 06-15-2019, 06:34 PM Thread Starter
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Rather odd that three cars would be doing that. You say it's difficult to rotate the tire but not that it's really hard to rotate. Are the pad-notch, slide/pin surfaces clean and rust free? And lubricated it the pin goes thru a sleeve?
Yes, everything is cleaned and lubricated. I grind the "ears" on the ends of the brake pad until it moves with veer little friction. All surfaces that have contact with others are then lubed. When completed, everything moves with no binding. This seems to last a very short time as the pistons become "stuck" once again. I will inspect or replace the seals.

The experts with whom I have discussed this issue all agree that the pads are designed to drag a bit. However, I was taught that the boost/seal is designed to slightly retract the piston to prevent the pad from dragging on the rotor.

Thanks for the reply,

leomat
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post #4 of 11 (permalink) Old 06-16-2019, 02:37 AM
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Very good practice doing the grinding and lubing.
Next thought would be dirt or grit buildup on the "tuck-back" S-roll in the seal rubber that allows it to move in and out with the piston without stretching the seal. Or hardened rubber.
You'll find out when inspecting the seals, and may be able to arrange blocks in between the caliper sides to allow piston(s) one side at a time (if two-sided pistons) to extend just out enough to get a look at the seal roll.
.02 and a half cents.

zippityzda
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post #5 of 11 (permalink) Old 06-16-2019, 11:56 AM Thread Starter
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Very good practice doing the grinding and lubing.
Next thought would be dirt or grit buildup on the "tuck-back" S-roll in the seal rubber that allows it to move in and out with the piston without stretching the seal. Or hardened rubber.
You'll find out when inspecting the seals, and may be able to arrange blocks in between the caliper sides to allow piston(s) one side at a time (if two-sided pistons) to extend just out enough to get a look at the seal roll.
.02 and a half cents.
Hi Dumbstone:

Thanks for the reply. I will check the seal to see if it has been damaged or is dirty.

I just replaced the entire caliper about a year ago and have driven the car less than 200 miles.

Perhaps I am using the wrong grease to lube the piston. I have been using chassis grease which may turn hard with time. I think that Toyoto sells a copper based grease for this job. Perhaps I should invest in some of this grease.

I may be reading too much into Stuck calipers.

Thanks for the reply.

leomat
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post #6 of 11 (permalink) Old 06-16-2019, 05:12 PM
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Hi Dumbstone:

Thanks for the reply. I will check the seal to see if it has been damaged or is dirty.

I just replaced the entire caliper about a year ago and have driven the car less than 200 miles.

Perhaps I am using the wrong grease to lube the piston. I have been using chassis grease which may turn hard with time. I think that Toyoto sells a copper based grease for this job. Perhaps I should invest in some of this grease.

I may be reading too much into Stuck calipers.

Thanks for the reply.

leomat
I may have a solution for you. How new is the brake master cylinder? I had this same problem after installing one I got at an autoparts store. The reason some of these don't work for our cars is the piston is too long and blocks the return hole inside the master cylinder so the brakes never release.

If the problem started after you installed the new master cylinder then that's the issue. I ended up getting this one and it fixed my problem:



1978 280z - stock L28 engine - Dallas, TX
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post #7 of 11 (permalink) Old 06-17-2019, 02:59 AM
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Originally Posted by leomat View Post
Hi Dumbstone:

Thanks for the reply. I will check the seal to see if it has been damaged or is dirty.

I just replaced the entire caliper about a year ago and have driven the car less than 200 miles.

Perhaps I am using the wrong grease to lube the piston. I have been using chassis grease which may turn hard with time. I think that Toyoto sells a copper based grease for this job. Perhaps I should invest in some of this grease.

I may be reading too much into Stuck calipers.

Thanks for the reply.

leomat
It would depend on the chassis grease composition. For brakes the grease should be for high temperatures, like lithium complex. One grease, and there are equivalents, is Lubrication Engineers lithium complex, NGLI grade 2.

zippityzda
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post #8 of 11 (permalink) Old 06-20-2019, 08:28 AM
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Originally Posted by leomat View Post
Hi Dumbstone:

....Perhaps I am using the wrong grease to lube the piston. I have been using chassis grease which may turn hard with time. I think that Toyoto sells a copper based grease for this job. Perhaps I should invest in some of this grease.

I may be reading too much into Stuck calipers.

Thanks for the reply.

leomat
Very much the WRONG grease. Brake pistons are generally lubed with ONLY brake fluid. You will need to strip, clean, replace contaminated seals and flush. If you are talking about the slide pin, then 3M silicone is among the best. Chassis grease is wrong here too. Requires high temp specialty brake pin lube. You have to remove the calipers, clan out all old grease and start fresh.
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post #9 of 11 (permalink) Old 06-20-2019, 01:53 PM
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"Every time I check my brakes, the pistons are stuck making tire rotation difficult." This sure isn't something I check very often - do you check because you notice dragging brakes? Antoher reason? And how do you know they're actually stuck - you would have to remove or at least hinge the caliper up to check that.

The Master Cylinder suggestion is a good one, but since, from what you say, it's happening to three cars at the same time, and the only thing they have in common is the grease you're using for the pistons (I agree with JWS360 - no grease!), then that may well be your culprit.
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post #10 of 11 (permalink) Old 06-21-2019, 02:47 AM
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My bad with specificity. Talking about the slide pins/sleeves, not pistons. If he's asking about where to get and how to rebuild pistons/seals, he's probably not talking about "pistons".

zippityzda
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