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Magic formula for pushing pistons?

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Old 13 February 2006, 02:12 PM
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k2iss
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Angry Magic formula for pushing pistons?

Hello,

I tried to change my front pads with a pair of new greenstuff. I couldn't push any of the piston backs...

What's the trick here? I read here that it was easy to push them back by hand, but there was no way I could have done that...

Do I need to remove the entire caliper?

How do you do that? Please I need good and quick help my old pads are totally worn...


Cheers,
Kriss
Old 13 February 2006, 02:35 PM
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scoobie-shieldy
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remove the brake reservoir cap, as u r trying to pushg back all that pressure also

o and dont forget too put a rag around the inlet, or it could get very messy
Old 13 February 2006, 02:56 PM
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Buy the tool for the job: - a piston spreader


http://www.toolmix.com/browse/produc...=269&pid=58312
Old 13 February 2006, 03:30 PM
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Or use a small g-clamp
Old 13 February 2006, 08:34 PM
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k2iss
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Okay, I'll try that. Thanks for the quick answer guys
Old 13 February 2006, 08:38 PM
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How did you get on? Im going to attempt mine in a few weeks I think

Iain
Old 13 February 2006, 08:40 PM
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Doh, just noticed your post time
Old 13 February 2006, 10:28 PM
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RON
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I normally use a wide screwdriver against the old pad before i remove them.... never had any trouble..... maybe the pistons are stuck a bit???
Old 14 February 2006, 07:39 AM
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911
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Just done mine.
Exactly as Ron says.
On 4 pots the trick is to remove just one pad and then return the pistons with a wide driver (or the proper tool!). Sometimes the one piston will creep forward as you depress the other as the fluid transfers. This is a very good sign as the pistions are very free moving!
You should not need undue force to do this. If you do then something is wrong, ie corroded pistons etc.

Remember to replace the small spring set into the corner of each pad. This stops the car clonking as you brake in reverse then braking going forward.
They are a tight fit.
Also get everything clean and free of rust and road debris.

Graham (practicing to get 5 spanner Haynes rating for 30 years now...)
Old 14 February 2006, 12:33 PM
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messiah
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Originally Posted by 911
Just done mine.
Exactly as Ron says.
On 4 pots the trick is to remove just one pad and then return the pistons with a wide driver (or the proper tool!). Sometimes the one piston will creep forward as you depress the other as the fluid transfers. This is a very good sign as the pistions are very free moving!
You should not need undue force to do this. If you do then something is wrong, ie corroded pistons etc.

Remember to replace the small spring set into the corner of each pad. This stops the car clonking as you brake in reverse then braking going forward.
They are a tight fit.
Also get everything clean and free of rust and road debris.

Graham (practicing to get 5 spanner Haynes rating for 30 years now...)
small spring? I get a little clonking occasionaly, can you explain a bit more for a numptie please?
Old 14 February 2006, 06:54 PM
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360ste
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In the past I saw, somewhere, that forcing fluid in the opposite direction through the ABS system was not a good idea. Don't know how truthful this is , so I have always opened the bleed nipple on that side of the caliper, having fitted a blled pipe first, as I push the pads back. One benefit of this the cooked brake fluid is expelled and replaced with fresh. Also if during the last bleed of the brakes any air is still in the system it will be expelled too. Just make sure to keep the reservoir topped up to prevent air entering the system. Steve
Old 14 February 2006, 07:12 PM
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IanK Spec C
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360ste is right, it not good practice to push dirty fluid back up. It's better to expel it via the bleed nipple when pushing the pads back. Also take care if not using a brake pad spreader to not damage the disc or pad face with the screwdriver.

Best regards,

Ian
Old 14 February 2006, 09:19 PM
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k2iss
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Originally Posted by IAN K UK300
It's better to expel it via the bleed nipple when pushing the pads back.
It sounds to me like a good way to screw things up... I don't even know what a bleed nipple looks like
And what happen if it bleeds too much, like the last time I bled my central heating radiators...

I also tried with a big screwdriver but the piston didn't move more than one millimeter. Also my scooby is only one year old, I can hardly believe that the piston is stuck or rust.

I'll do a second tentative this weekend, I'll see if I can find the proper tool tomorrow.
Old 15 February 2006, 07:49 AM
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911
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K2iss:
With the very greatest of respect to you, are you sure you should be doing this if a bleed nipple is unknown to you? Please do not take offence, i don't intend any to you.
The car is 1 year old, so why not return it to the Dealer?
Those pistons should fly back!

Messiah;

The small spring is a small (half a postage stamp in size) 'leaf' spring with an extended finge that locates along the edge of the pad and the caliper slot for the pads.
It is slightly arched to give a small degree of compression/spring back.
It's purpose in life is to take-up the clearance between the pad and the caliper to stop the pads moving in the caliper too much when brakes are applied.
The common clunking sound when braking in reverse is stopped by this small device. No real harm if you leave it out, you just get clunking!

Graham.
Old 15 February 2006, 07:31 PM
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k2iss
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Originally Posted by 911
K2iss:
With the very greatest of respect to you, are you sure you should be doing this if a bleed nipple is unknown to you? Please do not take offence, i don't intend any to you.
Well I have changed a couple of times my brake pads on different cars, but never on the scoob. Effectively I never bled the brake, because 1) it is only a good practice 2) Nobody has been kind enough to explain me how to do it.

Originally Posted by 911
The car is 1 year old, so why not return it to the Dealer?
Those pistons should fly back!
Because last time I went to my BMW dealer to check for a brake light not functionning under warranty, it costed me £250. Last time I had an oil dipstick problem on the scoob it costed me £50 (on a 6month old cars).
If I have a problem with changing the pads, I'd rather to be sure the piston is stuck before paying a guy a couple of hundreds to play with a hammer on my car and emptying my wallet.

No offence 911, but I'm not sure you've been of a great help on that topic.
Old 15 February 2006, 10:24 PM
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360ste
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K2iss. To help further, dependant on the type of brake caliper fitted the bleed nipple might be in a slightly different place but. On my bugeye STi they are located at the top of the caliper one on each side of the caliper. They normally have a rubber cover that can be a bit fiddly to remove especially if you have fingers like pigs ****. Lift off this cover it should be connected to a loop that is under the actual bleed nipple. Next find a ring spanner that is a good fit on the hex on the bleed nipple and try to loosen it off 'DO NOT TRY TO FORCE IT EXCESSIVLY' because if it snaps it can be a right swine. If it is tight protect the rest of the brakes with a rag and CAREFULLY spray a bit of WD40 or equivalent and leave to soak for a hour or two. If you loosen the bleed nipple easily re-tighten leave the spanner in place and fit a bleed pipe, These have a ball valve in one end so that when bleeding the brakes yourself it is a lot easier and a softer piece of rubber on the other end to fit over the bleed nipple and being retained by a plastic clip attatched to the pipe itself. Witht the end of the pipe in a suitable container open the bleed nipple and carefully push on the pad to ease the piston/s back into their bore. Remove that brake pad and fit the replacement now do the same process to the other side of the caliper. Once both pads have been fitted and the retainig pins fitted pump the brake pedal a couple of times to take up the space between the pads and disk. Check brake fluid and top up if necessary. Believe me it is brown trouser job if you were to changes bothsets of pads on the front or rear without taking up the freespace before driving off also you will probably then need to waste more time bleeding the air out of the system if you have emptied the master cylinder. I know this is a bit long winded but will hopefully clear up any problems you are having. just remember the bleed nipple is likely to be at almost the hihest point on the caliper to allow any air to easily be removed. If I have a picture I will put that in a reply so you can see what a bleed nipple looks like. Best of luck Steve.
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