Rear brake sticking please help!!

Lee Goodall

Lee Goodall

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Driving to work today a squealing sound started to come from the driver's side rear wheel!! I stopped to investigate and the wheel was hot and the brake caliper even hotter.

I jacked the car up at work and tried to spin the wheel.. it could be pushed around by hand but would not spin freely.

Obviously the brake is not releasing properly.. How do I go about finding and solving the problem?
 
Hopefully its just the sliding pins, if you undo the 2 13mm bolts and slide the caliper out of the way, hopefully you will find one/both of the pins no longer slide freely.You need to work it with wd40 or similar to free them, then remore completely to clean out as best as is possible.Get some wet and dry to clean the pins up, copper grease the pins and re insert. They should now move freely.re assemble.

If however they are fine, the piston could be sticking, thats more difficult to deal with as they need to be wound back and usually have split boots/seals that lets water in and rusts the piston. Maybe some wd40 and winding will free it temporarily or maybe it wont,you would need to try it to see.

HTH
 
audi upgrades
i would use something a bit more substantial than copper grease on the sliders

copper grease is intended to be used as an anti sieze compound, not a general lubricant for brake caliper sliders

general purpose grease will work better, moly or silicon grease probably better still
 
Fair enough, i have found in high heat applications that normal grease seems to "run away" and no longer provide protection over the sliders.
 
Arrrrggghhh.. Checked the pins, they're fine and packed with grease and the pads are hardly warn. I cleaned everything off and tried wd40 all around the piston, copper greased the back of the pads and put back together.

The wheel could be spun by had with the car on axle stands now.. went for a quick drive, jacked her up again and it's sticking again.

Is it the piston sticking?.. could there be any other causes.

If it is the piston what is the best route to fixing it? Fit new caliper? or is there a repair kit etc?:doctor:
 
DO NOT USE ANYTHING BUT COPPER GREASE NEAR THE DISC!!!

Copper grease has a really high melting point, if you use GP or moly grease then when your brakes get hot the grease will liquefy and run onto the disc.

Do the pads move freely in the caliper housing? the pads may be sticking on their edges to the caliper, try cleaning that portion up with a scraper/wire brush.

The piston is unlikely to seize unless the boot is displaced or damaged in some way, you can test it by removing the caliper and having someone press lightly on the pedal to see if the piston moves.
You'll most likely need a caliper retractor tool (halfords about 12 quid) to wind it back in, it will be stiff but not impossible.
 
That will be the piston sticking.I dont believe you can get caliper repair kits any more, more likely you need a recon caliper ( ebay have had new ones for unde £40) at around £60 or a used one
 
I'll dismantle the brake and get someone to press the peddle to check for movement and try winding the piston back.. if it still sticks then I'll look for a new caliper because there's obviously a problem.

Yeah.. I'll have a look on ebay if not I'll probably use Euro Car Parts or GSF.

Cheers.
 
..oh yeah when you wind the piston back is it best to bleed fluid off so I don't cause any leaks?
 
I had this problem with my avant, split gaiter on the piston caused the surface to corrode, i temp fixed it by cleaning up the piston with some wet & dry, but not a permenant fix.

you shouldnt need to bleed off any fluid, just leave the cap off the resevoir and it will be forced back through when you wind the piston in.
 
You don't want to move the piston too much, you wont need to bleed any fluid.

How old is the car?
 
yea, i would be careful using normal generic 'grease' in high heat aplications. copper ease always on brakes. and always make sure you have the right grease on your wheel bearings too! the previous owner of my brother skoda rapid sport smashed what ever he wanted in there... the result a complete lack of brakes on one wheel and:

DSCF1866.jpg


DSCF1869.jpg


DSCF1868.jpg


yup, the weird red grease over heated, and made an exit from the hub, all over the disc, pads, caliper, and wheel!

use the right stuff...
 
Def will stick to copper grease for anything high friction/heat.. think the evidence proves it's an issue!

My A4 is 1996.. should I replace the caliper to be certain of a proper fix?
 
Well thats up to you, i didnt want to mention the wet and dry method in case anyone thought it too unprofessional/ dangerous etc etc
But as a short term measure i am sure you could allow the piston to extend out a bit clean it ( mayb a tad of grease to stop ingress of water and wind it back in. Obviously while you find the replacement ;)
 
i didnt say to use normal grease on the pads, or anywhere else on the caliper bar the sliders.

Go buy a new caliper and you'll find it comes with clear silicone/synthetic grease for the sliders, not copper grease.

Copper grease is NOT a lubricant for moving parts. its an anti seize compound. Which is why you use it on non moving parts like the back of brake pads and wheel nuts.

Infact a quick google seems to suggest that using copper grease on the sliders can damage the dust seals. so even more reason to avoid it.

Silicone grease on the sliders is the way to go. Keep the copper grease on the back of the pads and on the bolt threads to stop them seizing.

Anyway, the early cars (pre 97 i think) had cast iron calipers and the later ones were alloy, the cast iron ones were known for sticking. If you change the caliper try to get yourself an alloy replacement.
 
Yeah it isn't copper grease on the pins.

I will try to get the piston moving smoothly as I can't see any sign of damage but if it doesn't work I'll get a new caliper. Probably try the wet and dry method lol

Will the alloy caliper be a straight swap? Actually I've got a copy of ElsaWin so I'll have a look to see if the design differs in any way.
 
i hope it is a streight swap. My 96 also has something dodgy going on with the rear brakes. im not sure if they're sticking (no heat) but one disk seems badly pitted and scored.

gonna strip it down at the end of the month and see whats going on. I'm hoping i'll get away with new disks and pads but ive got a niggling feeling that its going to need a caliper or two while im there.

Let me know what you find
 
Yea sorry, my point was more to make sure you use the right grease i nthe right places, especially as there is some pretty cheap and nasty stuff out there! i should have been more clear.

i didnt realise you shouldnt use it on the pins though. in hind sight, that makes sense.
 
The pins will work perfectly well with no lubrication at all. the grease is there just to stop corrosion. its not the same principle as a wheel bearing or a cv joint.
I was told and have always used copper ease on brake components. I did 3 years at college and 2 further years in a garage so I think my opinion is not just a DIY one.

The fact that copper ease is not a lubricant is not a deficiency in this capacity in fact it works to your advantage by not dripping everywhere and lubricating the disc.

I think you should also change your brake fluid, it should be done every 2 years anyway.

Its a shame it wasn't your front caliper sticking I have a set of perfect ones!
 
Give it time and I'll probably need front calipers too the way my luck's going lol

On the bright side my new MAF sensor came today:sm4:
 
you might want to check the handbrake mechanism too, thats more likely to bind up than the piston.
 
aragorn said:
Infact a quick google seems to suggest that using copper grease on the sliders can damage the dust seals. so even more reason to avoid it.

Silicone grease on the sliders is the way to go. Keep the copper grease on the back of the pads and on the bolt threads to stop them seizing.
Click to expand...

Sorry, no offense but that's balls, how is the copper grease going to get from the pins to the seals? It only needs a smear not a buttering like its toast.
Your statement is a contradiction in terms. You say to not put copper ease on the pins but put it on the back of the pads? Which is closer to the dust boot, the back of the pad or the retaining pin. Hmmmm

Silicone grease is for electrical contacts mostly, it no use in brakes. It melts and runs off at about 170 degrees unless its contained.
 
nickkeyser said:
ok, i will keep my 'diy' opinion to my self.
Click to expand...

Just so everyone knows I was not having a pop at anyone, merely pointing out dangerous practice. And it certainly wasn't aimed at nick, in fact he concurred with my sentiments. Make up your own minds.
 
audi upgrades
the seals i was referring to are the seals around the sliders not the dust boots on the main pistons

i can however see your point with the copper grease being used on the back of the pads near the dust seals however this is generally only used as a light smear.

I've fitted two new rear calipers to my dads mazda recently and both came from the supplier with the sliders pre-filled with a clear grease. Other calipers ive fitted have been supplied with a tube of grease for the sliders and again it was clear.

I dont doubt your experience in various garages, but i do know i dont put my car any where near any garages simply because i dont trust the people working there to do to things properly. Your garage experience should tell you that grease and oil damages rubber.

I also know i wouldnt be putting copper grease on the sliders of my brake calipers.
 
Extended the piston, cleaned it all off with wet and dry paper (it did need it), wound it in, let it back out again a few times and smeared a tad of grease around the base.

Still sticking so my thoughts are going towards the handbrake mechanism as A4Quattro said.

I'll investigate if it ever stops raining (should really clear out my garage)!!
 
Checked the handbrake mechanism and it was working correctly.
I put the sticking down to corrosion on the piston.

Got a remanufactured caliper from my mate at Parkers (with some discount).

Fitted the new caliper over the weekend and now I'm back on the road :blackrs4:
 
good stuff, should feel worlds better now and prevent any further corrosion.
Job well done.
 
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