Brake caliper windback tool and stiff caliper

[jon hill 3Participant @jonhill3]

Hi Guys

I decided to replace the disks and pads on my 15 year old astra.  After watch many youtube videos and consulting the haynes manual I am still at a loss as to weather the caliper needs to be rotated to push it back in?  I was working on the assumption that the caliper (not the guide pins) are able to free rotate and thus any pressure on them should push them back regardless?

I ask because I had some resistance with retracting mainly the rear single piston calipers, I did use a lot of wd40 and loosened the resovoir cap after extracting 100ml or so of brake fluid from the tank.  I didnt open the bleed valves as I didnt want to introduce any air or get brake dust into the fluid.

Any ideas?

[Craig BrownParticipant @craigbrown60096]

Some rear disk brake calipers require the piston to be rotated to get them retracted. I believe it is to do with the hand brake operation. If there has been no mention, in the Haynes or YouTube videos, about the need for a windback tool then I would think it doesn’t need one. I normally use a small clamp to help push the pistons back, very little pressure required just easier than pushing by hand

[Robert Atkinson 2Participant @robertatkinson2]

To confuse things it depends on shat brake system is fitted. It is not unusual for a particular model to have different brake components and even manufacturer depending on exact specification, fuel or even when / where it was built. I had a Fiat Croma which has the same running gear as a Vectra “C” and this had several different brake combinations. On mine the rear pistons had to be rotated but determining the direction was difficult.
Maybe better looking on a Astra forum. Probably got picures and videos.

[David JuppParticipant @davidjupp51506]

Wind back direction for the piston is typically reversed from side to side on the car – so ideally you need 2 variants of wind back tool, or fiddle about a lot on one side.  Often easier if you crack open the bleed nipple on the calliper too – this also avoids back-flushing seal wear debris into the ABS unit (which can lead to very big bills).

I can never remember which way to turn the pistons on my wife’s car – have to use trial and error each time.  At a push you can do it with a pair of long nosed pliers, but the wind bank tool does help.

If the handbrake cable connects to the callipers, the piston will need turning to wind the internal ratchet back down the threaded shaft.  If the car has separate brake drum/shoes for handbrake, then no need for winding back – just push.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi John Hill, I had to do that job on my last Astra that I had, it’s not just a matter of winding them back, as you have to apply some pressure to it at the same time as rotating it, there is a tool for the job, but I think they were quite expensive when I looked, so I just used a G clamp, and a pair of water pump pliers, although it was a slow process.

Regards Nick.

[Dave HalfordParticipant @davehalford22513]

Wind back pistons will have a slot.

[FulmenParticipant @fulmen]

Tip: Unhook the protective bellow from the piston before turning the piston. Last time I did this it got pulled out from the groove in the caliper, requiring a disassembly (and subsequent bleeding).

[Nicholas Farr]

On Nicholas Farr Said:

Hi John Hill, I had to do that job on my last Astra that I had, it’s not just a matter of winding them back, as you have to apply some pressure to it at the same time as rotating it, there is a tool for the job, but I think they were quite expensive when I looked, so I just used a G clamp, and a pair of water pump pliers, although it was a slow process.

 

They’re so cheap it’s not worth improvising – LINK

I bought a very similar set for <£20 over ten years ago, and it works better than just a G-clamp to push back plain pistons.

[Nick Wheeler]

On Nick Wheeler Said:

On Nicholas Farr Said:

Hi John Hill, I had to do that job on my last Astra that I had, it’s not just a matter of winding them back, as you have to apply some pressure to it at the same time as rotating it, there is a tool for the job, but I think they were quite expensive when I looked, so I just used a G clamp, and a pair of water pump pliers, although it was a slow process.

 

They’re so cheap it’s not worth improvising – LINK

I bought a very similar set for <£20 over ten years ago, and it works better than just a G-clamp to push back plain pistons.

Hi Nick, they may well be cheap now, but when I wanted one, they were more expensive than my available funds would allow then.

Regards Nick.

[jon hill 3Participant @jonhill3]

Rightly or wrongly I used one of those universal windback kits but didn’t rotate the piston on the real calipers.  It seemed to work but I ended up using an extension tube on the rod attached to the threaded bar which bent. Could have been the chinese steel or possible some excessive force.  I would imagine brake dust gets stuck in the piston and seal or possible the boot might get trapped in the oring.

Hopefully the abs wasn’t damaged in the process… anyway it passed the mot not that that is any guarantee against hidden problems.

On the whole I think £11 for a universal caliper windback set is amazing value, if anyone can build a better one for less money I would like to know 😉

[Neil LickfoldParticipant @neillickfold44316]

Look at the seal boot. If it is cracked or damaged, you may have a partial rusted piston. Pushing it back in will cost you the cylinder. Did my daughters car recently. Replaced the piston and boot seal was the easy option. Replaced and changed the brake fluid while at it. They had rusted on the outer edges and winding them back in would have damaged the cylinder.  Her one has the hand brake on the caliper. and the pistons have a threaded internal setup.

Got the seal kit and new pistons.

Non rotating have no slots for the rewinding tool.

Neil

[Howard LewisParticipant @howardlewis46836]

Not unknown fo a vehicle manufacturer to use components from different suppliers, or different sizes.

I have seen, many years ago, service lettrers, from a multi national manufacturer, saying that, on one day, a particular size of component was unavailable, so variation was fitted.

So the specifeid 3/4″ master cylinder have might become 5/8″ for a few hours.

Certainly, this happened on the garage Land Rover, and we found out the hard way!

Investigating alternative suupliers of a component showed varying results. One “spurious” spare incorporated a defect that we had found and had corrected.  Another, was superior to the current supplier’s product!

So it pays to check very carefully, before doing anything too drastic.

Howard

[jon hill 3]

On jon hill 3 Said:

Rightly or wrongly I used one of those universal windback kits but didn’t rotate the piston on the real calipers.  It seemed to work but I ended up using an extension tube on the rod attached to the threaded bar which bent. Could have been the chinese steel or possible some excessive force.  I would imagine brake dust gets stuck in the piston and seal or possible the boot might get trapped in the oring.

Were you turning it the correct way? That’s why the kit I suggested has two winders; one of them has a left hand thread. Having used mine several times, there doesn’t seem to be a consistent reason for where LH thread are used – that can be both sides, one or neither.

[jon hill 3]

On jon hill 3 Said:

Rightly or wrongly I used one of those universal windback kits but didn’t rotate the piston on the real calipers.  It seemed to work but I ended up using an extension tube on the rod attached to the threaded bar which bent. Could have been the chinese steel or possible some excessive force.  I would imagine brake dust gets stuck in the piston and seal or possible the boot might get trapped in the oring.

 

These pistons have a spring on a shaft inside them that behaves like an infinite ratchet. Turn one way the spring tends to open, turn the other way the spring tightens and locks the piston.

All disc calliper’s normally operate by moving out which distorts the seal. Releasing the pedal relaxes pressure on the seal which returns to normal and pulls the piston back.

With a handbrake calliper the cable pushes the spring rod which pushes the piston, the spring prevents back sliding but also allows for pad wear.

Surprisingly little dust gets under the dust boot.

A stuck piston will always be the result of a rusty piston or corroded calliper (which is normally limited to the section between the boot and seal, which will not affect future braking once removed.)

[bernard towersParticipant @bernardtowers37738]

Sorry Howard but changing a master cyl dia by 1/8” would dramatically change the driver effort and pedal travel to a degree that could make it difficult to control the feel and travel of a the pedal and to a degree driver fatigue. On the other hand if changing  the dia to smaller the effect would be the opposite. I speak from experience of doing this on custom cars in the early 1970s. This effect is magnified when the fashion was to fit a girling powerstop or similar to increase stopping power.

[Howard LewisParticipant @howardlewis46836]

Bernard,

I agree but not enough to make the vehicle dangerous. This sort of thing did, and probably still does, happen.

I often saw Service Bulletins from the multinational manufacturer of some of the staff vehicles in our fleet (1,000 vehicles) saying things to the effect of “On the afternoon of “date” we ran out of 3/4 master cylinders and fitted 5/8 until supplies resumed”

And when we needed to refurbish the master cylinder on a depot Land Rover, the local agent supplied a kit which was too small, (The Company had bought three vehicles at the same time), so the practice was not confined to one manufacturer.

I have seen this from both sides.

In a high volume manufacturing environment, very often, in such circumstances the motto is “Where needs must, the devil drives”.  I have been faced with a situation of being told “You have two minutes to make a decision. If you say NO, nightshift will have nothing to do”.  In that case, I did say “NO”. Had I said “Yes”, they would only have scrapped a lot of material requiring total rebuild of every machine.

So you can understand why fitting a slightly over or undersized master cylinder would be better than bringing  an assembly line to a halt.

Howard

[old martParticipant @oldmart]

I recently did my Corsa D 1.7 CDTI using one of those super cheap boxes of windback tools. The left side needed winding anticlockwise using the left handed thread tool and the right side was clockwise using the right hand threaded tool. Each time I clamped the short flexible hose with some made for the job plastic locking pliers and cracked the bleed nipple with a hose down to a jar. The hydraulic fluid is discarded rather than possibly contaminating the ABS unit. I had to wind the pistons right back pretty well level to allow the new pads to slide in over the new discs. The Haynes manual is vague about the whole proceedure, and only the Astra manual has the rear discs and the 1.7 engine in it, the Corsa manual only has the 1.3 diesel and 1.2 petrol engine vehicles. My system is Bosch.

[noel shelleyParticipant @noelshelley55608]

I have known a perfectly good braking system to fail when it is bled ! The master cylinder valves open and on longer work. I have also known new master cylinder valves to not seal, making them useless. Cars with as many as 3 different choices of brake manufacturer and no note of when changes were made. A nissan where you could push the piston back past the seals, a Fiat that as the pads wore could throw the pad out.  DOT 5 fluid can be silicone or ethalene base.  And so it goes on. Noel.

[CirclipParticipant @circlip]

And to keep up  with the latest teknowleggy, a mate recently informed me that replacement of the rear pads on his car needed the use of a computer to pull back the pistons on the rear calipers of his car fitted with the automatic hand brake system. Unfortunately, although completely standard, the program(me) didn’t pull the rear pistons back as it was a different model although a main agent for the car.

Obviously missed the Tuesday night reprog.

Regards  Ian.

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