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Problems fitting brake pads


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#1 adam c

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Posted 28 May 2004 - 06:39 PM

The other day there was a noise coming from the OS of my mini when braking, I thought it might have been the CV or somit but Dklawson recommended changing the pads and they needed changing anyway so thats what i did today...

The OS went on fine, the old pads had about 4mm on them so needed replacing. I then got to the NS and pushed one piston back fine but the other one would not budge and after about 20 mins trying I still can't get it to budge so have had to leave it for tonight.

Basically is it possible that the piston has siezed (i think this happened to charliebrown recently) and if it has are new/reconditioned calipers the only way forward and i presume I would have to do both sides at once?? As always something goes wrong on a bank holiday so I will have to wait till tue if i need any parts. Any sugestions would be great........

#2 bluebottle

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Posted 28 May 2004 - 07:02 PM

if they are the 's' calipers they are quite easy to rebuild, i did mine a couple of years ago now.

i bought new seals, stainless pistons(so they wont rust again), the split line seal, and the dust seals, the whole lot came to about £50 ish, brakes are awesome afterwards, you dont realise just how bad they are till you get them right!

#3 dklawson

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Posted 28 May 2004 - 07:04 PM

I didn't realize this was a holiday weekend in the U.K. also. Sorry about the timing.

You don't necessarily need new calipers. The original Lockheed piston design was chrome plated steel. The OD of the piston starts to corrode and seizes the piston in the caliper bore. What you will need is a new piston (the good replacements are stainless steel, not chrome plated), and a rebuild/seal kit. Once you've got the parts to do the rebuild you don't have to be "gentle" getting the old piston out. If it is only stuck a little, clamp the free piston with a C-Clamp (so it can't come out) and apply compressed air to the brake hose port. (Make sure the stuck piston is pointed away from you and that the caliper is wrapped in a towel to catch the brake fluid). If that doesn't work you have three other choices: 1) Make up a fitting to allow hooking a grease gun to the hose port. C-clamp the free piston, then pump the caliper full of grease. Keep going until the piston pops out. Grease guns develop several thousand pounds of pressure. 2) Grab the piston with a large pair of water pump pliers or mole grips and wrestle the piston out. Remember you are going to replace the piston anyway so damaging the old piston isn't a problem. 3) As a last resort, weld a small bar to the old piston and use clamps or a press to wrestle the old piston out.

If you use the grease gun method to extract the pistons, be sure to flush out the caliper with stronger and stronger solvents, then wash with degreaser followed by alcohol. Don't leave any grease behind.

The important areas on the caliper are the gland where the square-section hydraulic seal seats and the OD of the piston. If both of these are in good condition you will have a good rebuild. Some pitting of the caliper bores is OK, you don't seal on those surfaces. The hardest step is re-fitting the outer dust seal retention ring. This is a cup shaped sheet metal ring that must be pressed into the inside of the caliper (last step). Find or make a ring with a center hole just large enough to fit over the OD of the piston. Leave about 8mm of the piston sticking out of the caliper bore, fit the dust seal followed by the retainer, then your installation tool/ring. Work the rubber dust seal into the bore around the piston. Then use c-clamps to gently work the retainer ring into the bore behind it. Stop when the retainer is flush with the caliper casting.

by the way, the steps above were for 7.4" disks/calipers. I assume the 8.4" ones are similar enough for this to be applicable.

#4 adam c

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Posted 28 May 2004 - 07:08 PM

They are standard 8.4" calipers.
What is a split line seal??
Will it take me long to rebuilt them, I wouldn't get the parts from my local motor factors would I?? - Its just that i need them asap and they wouldn't come till tues if i ordered them and I've booked an engine crane for tues to get the engine out of my Mk3 so i'll be busy......
Thanks mate....

#5 adam c

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Posted 28 May 2004 - 07:11 PM

Ahh more sound advice dk :grin:
Sorry we were posting at the same time, looks like i'll have to try doing this on tues as well then - I might try getting up early!!
Thanks very much :grin:

#6 bluebottle

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Posted 28 May 2004 - 07:19 PM

the split line seal is, i think, only on the 's' calipers, where the two halves of the caliper are bolted together , there's a little 'o' ring which seals the joint. i wouldn't have normally interfered with this seal but it was leaking.

the other way of popping out your stuck piston is the clamp the free piston (three of them if you include the other side) and then depress the brake pedal, with a bit of luck, as its the only unclamped piston, it should come out.

i'd allow a morning to do both calipers, less if it goes well, more if not!

bear in mind that the 8.4" calipers are a lot cheaper than the 's' calipers, so it might be worth shopping round and seeing if you can pick up some new or reconditioned ones cheaply.

#7 adam c

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Posted 28 May 2004 - 07:24 PM

I think i might do both as if it improves efficiency this is probably a good idea. I will have a look at some prices now. I seem to remmber that there is a mini place is Stoke (quite near to me) so they might have some and might be open tomoz.
Cheers guys :grin:

#8 dklawson

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Posted 28 May 2004 - 07:24 PM

Good luck and once again, sorry about the timing.

The split line seal (if I am thinking correctly) is the flat sealing ring that goes between the two halves of the caliper castings. For a long time this part was not available. In the U.S. I think most people who have replaced it had to special order it from the U.K. because it hasn't been stocked here. Generally, you don't need to split the caliper to rebuild it so I don't do it. (If it ain't broke, don't fix it). It's your choice, but DON'T split the caliper apart UNTIL you have a new one of these seals. Have all your parts before you tear things apart. Good luck.

#9 adam c

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Posted 28 May 2004 - 07:27 PM

Thanks very much guys..I owe you both a pint :grin:
Have just seen the pistons for £7 and the seals for £2.50 in the mini place near to me so I might try and get me mum to take us in the mornin...

#10 bluebottle

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Posted 28 May 2004 - 07:29 PM

thats not fair!....i payed £9 a piston about 5 years ago!....prices are meant to go up , not down!

#11 Bluemini

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Posted 28 May 2004 - 08:45 PM

Mini Mine are in Stoke and they are fairly reasonably priced.

I normally go to my local scrapy and get callipers from there for a tenner...

#12 adam c

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Posted 28 May 2004 - 09:08 PM

Yeah cheers rich, thats the place i'm on about, will ring them in the morn to see if they've got any in. Will keep you posted....

#13 adam c

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Posted 29 May 2004 - 07:20 PM

Went down to mini mine this morning and they had loads of pistons and seals in stock. The whole lot for both sides came to £35 so not bad really.
However when I came to fit them the dust seals were an absolute *Female doggy* and it took me two hours to rebuild one caliper, so I worked on the philosophy that the other caliper was fine and that when you replace rear cylinders you only do one at a time so decided no to bother with the other one. I now have a great set of brakes but the noise coming from the OS is still there so I really have no idea what it is. Any suggestions??...
Thanks for the previous advice guys, I eventually got the dust seal in using a clamp and a steel plate - won't be rushing to do that job again!!

#14 dklawson

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Posted 31 May 2004 - 12:47 AM

Sorry the job was so difficult. That's why I was talking about making a plate with the hole in it which just fits around the piston... it's the easiest way to seat the steel ring. If you don't need your car right away, do the other side now. Don't wait. You'll end up duplicating all the brake bleeding and you'll keep putting it off until the car is dangerous. I don't have any more ideas about the noise but I'll keep thinking about it.

#15 Woody

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Posted 31 May 2004 - 05:27 AM

Check for play in your wheel bearing .




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