Yet another caliper thread! This time it refers to a fairly new rear right caliper (couple of years old at most). When attempting to change the pads today I just could not wind back the piston with the proper tool and clockwise rotation. The pads were well worn (weren't replaced when caliper was fitted) and the piston was some way out of its bore but the dust boot was fully intact and covering the whole piston. When I last did this on another caliper it worked just fine. Is it possible the piston is seized in its bore?
Technical Fairly new rear caliper problem
- Thread starter jim cooper
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Technical Fairly new rear caliper problem
Morning Jim,
It is possible it's seized, but usually with some brute force you can wind them back. They sometimes 'snap' free - you know like how a seized bolt suddenly lets go and you crack your hand on something cold and sharp! Other times it binds up on the seal like it's too tight and is never free enough to move properly. In that it'll want a rebuild or when I had an issue with mine I just replaced it for a good second hand unit - cheaper, quicker and much less hassle.
Also note that the Near side rear (passenger side in UK cars) is reverse threaded.
It is possible it's seized, but usually with some brute force you can wind them back. They sometimes 'snap' free - you know like how a seized bolt suddenly lets go and you crack your hand on something cold and sharp! Other times it binds up on the seal like it's too tight and is never free enough to move properly. In that it'll want a rebuild or when I had an issue with mine I just replaced it for a good second hand unit - cheaper, quicker and much less hassle.
Also note that the Near side rear (passenger side in UK cars) is reverse threaded.
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Thanks Artemis. I don't think I have enough brute force to apply so will get another caliper. Just a thought - this Bosch design seems to have created many problems for Fiat owners (and other makes no doubt). Time for a new design that is a bit more reliable in the longer term.
Well the last one of mine that got stuck I snapped my caliper rewind tool's shaft clean in half torquing on it - so they can get pretty well stuck! if it's that stuck probably better to just get a new one.
They can be a bit of a pain in the ass. People usually stuff up the NSR one trying to screw it in not realizing it's reverse threaded and damage the threads, so I'm a little surprises it's the other one that's gone on yours.
Still problematic they might be but at least they are plentiful and cheap to source.
dtimmins1985
Established member
Think im going to buy a set to keep in the shed, nowt worse than one failing and then having to wait and keep the car off the road until the new one arrives.
Have you taken the top off the reservoir?
Otherwise you're pushing fluid along the brake pipes into the confined space at the top of the master cylinder.
Ralf S.
Otherwise you're pushing fluid along the brake pipes into the confined space at the top of the master cylinder.
Ralf S.
Yes, I did that. Also, even with the caliper off the car the piston won't wind back. If I want a refund on my new caliper (remanufactured Bosch) the factor will have to accept the old caliper with the wind back tool jammed in it. Don't know how this happened because I only wound the tool the right way (clockwise for the driver side wheel).
Good idea
If it's any use I've just replaced calipers on mine- Euro Car Parts at Boucher had re-manufactured Pagids in stock for something in the region of £80 each.
You're really not going to believe this! It turns out the reason I could not wind in the piston on my driver's side rear caliper was because the piston had a left hand thread!!!
As a result it could be wound back in an anticlockwise direction but not in the recommended clockwise direction. This goes against all wisdom and advice re rear caliper and my main question is how this part could have been made in this way. It was a pattern part with no brand name on it. Is it possible to insert a left hand piston assembly into a right side caliper body during manufacture?
Something else that may not be generally known is a recommendation in the instructions for my new rear caliper (remanufactured Bosch). If you have to wind the piston in to get it to fit over new pads then you must wind it out finally half a turn in order to reset the mechanism. Is this right? The instruction was for Bendix calipers and a couple of other makes but it didn't mention Bosch by name. As I understood it you can only wind a Bosch piston one way.
As a result it could be wound back in an anticlockwise direction but not in the recommended clockwise direction. This goes against all wisdom and advice re rear caliper and my main question is how this part could have been made in this way. It was a pattern part with no brand name on it. Is it possible to insert a left hand piston assembly into a right side caliper body during manufacture?
Something else that may not be generally known is a recommendation in the instructions for my new rear caliper (remanufactured Bosch). If you have to wind the piston in to get it to fit over new pads then you must wind it out finally half a turn in order to reset the mechanism. Is this right? The instruction was for Bendix calipers and a couple of other makes but it didn't mention Bosch by name. As I understood it you can only wind a Bosch piston one way.
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Has anyone got any ideas on this conundrum?
They all turn opposite directions on opposite sides I can never remember which is which but you can feel which way is out as soon as you start turning it. A few sharp taps with a hammer to free them up helps with winding them back.
That's true but there has never been a report of a driver's side caliper needing an anticlockwise turn to wind the piston back.
That sounds odd...but without knowing what the brand is, it's impossible to comment.
It could be that "Brand X" always has an anti-clockwise wind-in on the driver's side, although as you say, someone would have mentioned it before. I also have "new" calipers... one is a Bosch (pimpled finsish) and the other is unmarked and has a smooth finish. I'll keep an eye on this one in case I need to wind it in some time.. (it arrived with the piston in exactly the right place, so I didn't have to wind it).
I think it's probably best to keep an open mind about which way the piston winds, when approaching a new caliper.. it could be either, by the sounds of it..
As of the other question, I had Budweg calipers on my Alfa 155 (re-cycled Lucas-Girling) and they came with the same instruction, that to get the minimum clearance they recommended you wind out the piston until you feel/hear the handbrake mechanism click, rather than just pumping the pedal until the pads touch the disc.
I doubt that pumping the pedal when there is a lot of clearance/piston movement is bad for the caliper - I got the impression it was just to make sure that the handbrake mechanism activated the pad onto the disc at the start of a "notch" rather than at the end of one, if that makes sense.
I think it just helps the handbrake get better leverage (although I have no idea how they work, handbrake is always the bane of my life and Dr Death the MOT man always grumbles about it
Anyhow.... I wound the pistons back by the absolute bare minimum just to fit over the pads.. pumped the pedal, worked the handbrake a few times... then removed the caliper, wound the piston in 1/4 turn and then re-fitted the caliper (pumped and levered as above) for good.
Ralf S.
It could be that "Brand X" always has an anti-clockwise wind-in on the driver's side, although as you say, someone would have mentioned it before. I also have "new" calipers... one is a Bosch (pimpled finsish) and the other is unmarked and has a smooth finish. I'll keep an eye on this one in case I need to wind it in some time.. (it arrived with the piston in exactly the right place, so I didn't have to wind it).
I think it's probably best to keep an open mind about which way the piston winds, when approaching a new caliper.. it could be either, by the sounds of it..
As of the other question, I had Budweg calipers on my Alfa 155 (re-cycled Lucas-Girling) and they came with the same instruction, that to get the minimum clearance they recommended you wind out the piston until you feel/hear the handbrake mechanism click, rather than just pumping the pedal until the pads touch the disc.
I doubt that pumping the pedal when there is a lot of clearance/piston movement is bad for the caliper - I got the impression it was just to make sure that the handbrake mechanism activated the pad onto the disc at the start of a "notch" rather than at the end of one, if that makes sense.
I think it just helps the handbrake get better leverage (although I have no idea how they work, handbrake is always the bane of my life and Dr Death the MOT man always grumbles about it
Anyhow.... I wound the pistons back by the absolute bare minimum just to fit over the pads.. pumped the pedal, worked the handbrake a few times... then removed the caliper, wound the piston in 1/4 turn and then re-fitted the caliper (pumped and levered as above) for good.
Ralf S.
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Thanks for this advice. The question of whether a piston can be wound both ways still puzzles me. My experience with Bosch calipers is that you can only turn the piston one way (i.e. inwards). Try the other way and it just won't move.
