Sticking Brake caliper

sooty · Unread post by **sooty** » 27 Jan 2006, 20:18

Found one of caliper pistons starting to stick. Is it safe to spray some WD40 with the thin tube onto the extended pistons, to help them from sticking or corrosion.

Unread post by **Peter.N.** » 27 Jan 2006, 20:28

Safer to lubricate with brake fluid. Oil is OK on hydropnumatic Citroens but will attack the seals on conventional brakes.

AndersDK · Unread post by **AndersDK** » 28 Jan 2006, 01:12

Correct lube is silicone-grease. In small bags either red or white coloured especially for brakes piston gym on conventional brakes.
Small cans of all-purpose clear silicone grease are also available.

Your local tyre specialist would have it in barrels for lubing rims when replacing tyres.

James.UK · Unread post by **James.UK** » 28 Jan 2006, 14:48

Hi Sooty, Silicone will certainly help a lot as Anders states. But I think the problem will keep recurring...

I had a lot of trouble with sticking callipers on my ZX untill I swapped them with Volcane callipers and vented discs.. To be frank I don't think the original callipers as fitted to a ZX are very good.

Check for any tiny holes in the rubber covers as its mainly dust from the disc pads that cause the problem.

I also think the Green pads produce less dust, and that also helps.

.

sooty · Unread post by **sooty** » 28 Jan 2006, 20:18

I'm sorry I did'nt mention that is on a Subaru STI with four pot calipers not a Citroen.

With these you are talking big money to replace or even with a service kit. It is only a temporary thing till some are found on such as on Ebay etc at a good price etc along with disc's as one is warped through heat from the stuck piston on along run.

Dave Burns · Unread post by **Dave Burns** » 29 Jan 2006, 10:22

Try a seal kit, I had the seals swell up on a fiesta, possibly because of wrong type of fluid but can't be sure, they were causing the discs to get very hot, the problem became clear when the new and old seal were seen side by side.

The new one would fit inside the old one it had swolen so much.

Dave

Kowalski · Unread post by **Kowalski** » 29 Jan 2006, 18:08

If you've got a stuck piston WD40 isn't going to be a whole lot of use. It takes quite a bit of friction to make a piston stick.

Dave Burns suggestion above sounds the most sensible. If you know what you're doing with brakes, take the caliper apart and have a look at the piston. An accumulation of dirt can stick a piston, a duff seal can too but chances are that if its corrosion (or flaking chrome) its time for a new caliper. You won't know until you get it apart and if you're lucky and careful you should be able to get it all back together again without needing new gaskets/seals...

bxbodger · Unread post by **bxbodger** » 29 Jan 2006, 20:16

Before you go spending pots of money, make sure its not just the flexible brake hose collapsing internally and not allowing brake fluid back up when you take your foot off the pedal-Its a pretty common fault and easy to check, just remove the hose and blow through it both ways-you'll notice any difference in resistance.

You may also find that if you try to bleed the offending brake not a lot of fluid comes through, a further symptom.

I'm sure i'm not the only person who has spent ages overhauling a caliper in the past before finding out it was just the hose........

sooty · Unread post by **sooty** » 30 Jan 2006, 21:45

bxbodger wrote:Before you go spending pots of money, make sure its not just the flexible brake hose collapsing internally and not allowing brake fluid back up when you take your foot off the pedal-Its a pretty common fault and easy to check.

I'm sure i'm not the only person who has spent ages overhauling a caliper in the past before finding out it was just the hose........

I know its none of what you've mentioned, because 3 of the 4 pistons moved freely and the 4th I could not move without brute force till it freed itself. Once I applied some lubricant and worked it out and back, its now OK for the time being.