caliper sticking

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dingo
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caliper sticking

Post by dingo » Tue Apr 26, 2011 2:25 pm

right front caliper: wheel spins slowly but grinds heavily on both pistons

remove pads, push back both pistons. replace pads. pump brakes. stuck again
" " " " ..still very sticky

will this work itself free eventually?

or is there some thing i can 'lubricate' with under the boots ??

[both boots in fairly decent shape, but ocean air is brutal here]
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Re: caliper sticking

Post by VWGirl » Tue Apr 26, 2011 8:39 pm

I think your efforts are futile on this... you likely have dirt or rust on the pistons which is causing them to stick...

Option one: go to your FLAPS (or autoparts store of choice) and get a caliper rebuild kit. If you can get the pistons out (compressed air in where the brake line goes will do the trick) then this is fairly easy to do.

Option two: buy rebuilt calipers... this can be tricky... i have found in the three times that I have bought calipers (from different sources might I add) that they tend to come in the wrong box... left is usually right and right is usually left... then there was that one time that I got two left calipers... but Colin happened to be by and carried a spare bolt, so I used two left calipers on my bus for a while. The second time I replaced mine (due to sitting and having your exact issue) I got a rebuilt caliper that had been rebuilt a few too many times and didnt have the right gap to fit my brand new pads with brand new rotor... and well the pins didn't fit either... but once I got it straightened out they work fine.

I went with option 1+2 the last time and when I couldn't get the piston out of one of my calipers I took them to a friend and he rebuilt them for me... I still have the calipers from the FLAPS on my bus (hey they have a lifetime warranty) and I have my original to the bus (now rebuilt twice) calipers in a box on the shelf so I can use them if the FLAPS calipers go out on me.

Good luck!

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Re: caliper sticking

Post by VWGirl » Tue Apr 26, 2011 8:41 pm

Oh... and I too thought it would free itself up eventually... and I drove about 400 miles (in one trip) with it scratching and screeching... for the cost of a new caliper and the hour or so of time to replace them BOTH I wouldn't try to wait it out again...

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dingo
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Re: caliper sticking

Post by dingo » Wed Apr 27, 2011 7:23 am

Thanks for the feedback and info !
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Re: caliper sticking

Post by Amskeptic » Wed Apr 27, 2011 7:29 am

dingo wrote:Thanks for the feedback and info !
Dang if she didn't step up to the plate . . .
Thanks VWGirl.
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 80,070 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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dingo
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Re: caliper sticking

Post by dingo » Thu Apr 28, 2011 2:10 pm

is there a possible other reason for failure to retract ?

It seems a longshot that both pistons would be jammed at the same time....

waiting for this dammed wind to subside....
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Re: caliper sticking

Post by VWGirl » Thu Apr 28, 2011 5:39 pm

If you stop to think about it, it really isn't unusual that they both would stop moving freely at the same time. both pistons are sharing the same hydraulic fluid in the caliper. The question is WHY are they sticking? Has the bus sat for a while? are your rubber brake lines good? what does your brake fluid look like? are you getting any air in the system?

Brake fluid is hydroscopic, so there is likely some water (even if minimal) in the system. The old steel brake lines can rust, and the rubber deteriorate in time. If the bus has sat for a long time it can develop a slight ring of rust/corrosion around the inside of the piston causing it to not move freely. If you take apart the calipers you will see that there is not enough room for a grain of sand to fit between the caliper body and the piston. there is no room for rust. If the rubber deteriorates on the inside a piece of it may come loose and end up stuck in the caliper as well. Changing your brake fluid regularly can help prevent caliper issues and brake failure.

The issue with my bus was that it sat for a year. the right piston was frozen. if I recall correctly, it was the inner piston that was super stuck and I could not get out with compressed air even. The other side came out with some effort. they both had a slight ring of rust.

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Re: caliper sticking

Post by Amskeptic » Fri Apr 29, 2011 7:12 am

dingo wrote:is there a possible other reason for failure to retract ?

It seems a longshot that both pistons would be jammed at the same time....

waiting for this dammed wind to subside....
Quick test!
Pump brakes firmly! Loosen brake line union at caliper! Does wheel release? Hose or master cylinder compensating port blocked.
Colin! No More Tornado Clouds Scuttling!
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 80,070 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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dingo
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Re: caliper sticking

Post by dingo » Fri Apr 29, 2011 11:26 am

Thx...that makes sense. The caliper does not actually stick in the 'clamped' position, rather, only retracts enough to turn but scrape loudly..both pads

Logically i should start with the master cylinder i guess...because the left side brake grabs quickly and immeadiately, whilst the right lags..only grabbing with the 2nd or third pump
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Re: caliper sticking

Post by Amskeptic » Fri Apr 29, 2011 4:20 pm

dingo wrote:Thx...that makes sense. The caliper does not actually stick in the 'clamped' position, rather, only retracts enough to turn but scrape loudly..both pads

Logically i should start with the master cylinder i guess...because the left side brake grabs quickly and immeadiately, whilst the right lags..only grabbing with the 2nd or third pump
A) it is normal to drag lightly, are your pads aggressive metallics that have not been used hard enough?
B) delayed response on one side only is usually a clogged hose that exacerbates dragging and not releasing. Do you have the spreader springs in place under the pins, they look like angular butterfly art.
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 80,070 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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dingo
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Re: caliper sticking

Post by dingo » Fri Apr 29, 2011 10:06 pm

Yes, i do have the butterfly spring.

clogged hose...sounds probable..will look into it.
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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static
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Re: caliper sticking

Post by static » Sat Apr 30, 2011 11:02 am

I have a similar issue to what Senior dingo is reporting. In addition to doing the procedure that he tried, I also bled enough of the crap out of the lines and replaced it with fresh stuff until it looked better. My brakes have improved, but once I am rich again I will invest in some rebuilt calipers.

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dingo
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Re: caliper sticking

Post by dingo » Sat Apr 30, 2011 8:21 pm

I thought youd be rich after your Chinese sabbatical ?? hehehe...

i did a quick bleed and went for a drive..seemed to have improved somewhat. Also noticed a loud clanging sound which went away when i hit the brakes...hoping it was just me forgetting to tighten the caliper bolts from the other day.

Silicon Dot 5 seems logical for coastal climates instead of the glycol...though i read that leaking brake boosters can deliver the silicon to your engine where it turns to sand...
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Amskeptic
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Re: caliper sticking

Post by Amskeptic » Sun May 01, 2011 10:15 am

dingo wrote: i read that leaking brake boosters can deliver the silicon to your engine where it turns to sand...
Interesting and horrible thought. Thanks for sharing that.
Colin
BobD - 1978 Bus . . . . . . . . . . .111,130 miles
Chloe - 1970 bus . . . . . . . . . . . 206,787 miles
Naranja - 1977 Westfalia . . . . . 80,070 miles
Pluck - 1973 Squareback . . . . . 55,510 miles
Alexus - 1991 Lexus LS400 . . . 72,113 miles

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