Toxico caliper, piston siezed

[hank]

I noticed my front brakes were bindng, so I loosened the left caliper and the wheel revolved freely. Ok so I removed the pads and pumped the brake lever to see what was going on, the inner pistons moved easily and the lower outer moved very slow the upper one didn't move. Outer pistons dont want to go back in.

Next I installed a set of worn out pads and retightened the caliper and was able to pump the stuck piston out enough to give it a clean. I gave all four pistons a good clean and lubed them with some fresh brake fluid.

Usually after doing this I can push the pistons back in by hand but not this time the top outer piston is not for budging. The lower one is only going back half way.

So I'm thinking it's time for an overhaul, has anyone had a go at splitting BMW (Toxico on the rear) calipers and replaced the seals. Haynes manual says it's a no go area and I'm not liking the idea of paying 160 quid for a second hand caliper.

 

[flatdog]

I noticed my front brakes were bindng, so I loosened the left caliper and the wheel revolved freely. Ok so I removed the pads and pumped the brake lever to see what was going on, the inner pistons moved easily and the lower outer moved very slow the upper one didn't move. Outer pistons dont want to go back in.

Next I installed a set of worn out pads and retightened the caliper and was able to pump the stuck piston out enough to give it a clean. I gave all four pistons a good clean and lubed them with some fresh brake fluid.

Usually after doing this I can push the pistons back in by hand but not this time the top outer piston is not for budging. The lower one is only going back half way.

So I'm thinking it's time for an overhaul, has anyone had a go at splitting BMW (Toxico on the rear) calipers and replaced the seals. Haynes manual says it's a no go area and I'm not liking the idea of paying 160 quid for a second hand caliper.

Don't go mad on the calipers until you check the brake fluid level is correct in your front reservoir. - Similar symptoms to what I experienced and reducing brake fluid level helped with the binding???

Otherwise if they have not been overhauled in the last 4 years then it's time to spend a bit.

 

[Steptoe]

Tokico calipers usually mean servo brakes ?

Be careful if so as flatdogs advice could cause you grief.

The fluid reservours are in the servo unit under the tank. Don't run them dry.

And if you push all the pistons back in any excess fluid will run out of the overflow pipe, which exits by the R/H brake footrest.
And push the pistons back in slowly because you can turn the seals in the servo unit inside out.

 

[hank]

Spot on with the servo advice Steptoe, but I removed the servo ABS was a long time ago. If I can get hold of the seals is it safe to split the caliper and pull the pistons out and fit new seals? I have seen people do this on other bikes.

 

[hank]

Caliper refurb kit is in the post from Sherlocks, will probably split the caliper tomorrow evening. Bleeding the brakes is the part I am least looking forward to, always been a bitch on this bike.

 

[bobsnew]

The service kit you get will not include the o ring seals between the calipers and are not available from BMW sources. The good news is I obtained mine from Kawasaki Cradley Heath and are stock items Kawasaki (part no. 43049- 1004) and Honda (part no. 45103-MEL-003) and are about £2.25 each.

 

[hank]

Cheers, Bob will phone local Kawa and Honda dealers in the morning see who has them in stock. Good to know they are available elsewhere. Some say that you dont need to replace the seals that go between the two halves, for peace of mind I would prefer to do it while I have the caliper apart.

 

[bobsnew]

Okay mate, sometimes necessary to split them to get the pistons out BMW don't supply the o ring seals as they don't recommend splitting them, but they wouldn't would they as they charge £300 for new replacement, it wasn't easy to split them, patience and brute force, good luck.

 

[hank]

I want to split them as I think it will be easier to get the old seals out and easier to clean all the crud out of the cylinders.

I have the caliper off the bike and the rear of the bolts are being soaked in wd40 to help release them. I dont have a decent vice so I will put the caliper back on the bike and crack the bolts in situ.

 

[bobsnew]

My experience, calipers off, continually soaking with WD 40 plus heat & pneumatic hammer across the bolt heads, not an easy task & came good eventually, dont forget the red brake grease.

 

[hank]

Ok, got the brakes fixed. Removed the banjo and put the end of the pipe in a finger cut from a latex glove held in place with a ziptie to stop all the fluid draining out.
Then I got my T40 socket and set about carefully losening the bolts that hold the two halves of the caliper together. First two bolts came lose ok, the third one didn't want to budge.
So I moved on to the fourth bolt, it gave a bit of a creak as it loosened the first quarter turn. I then went back to the stubborn third bolt and tried again,bang, I shouted a couple of four letter words and thought well thats me really in the crap now.

What I thought was the bolt shearing off was actually my T40 socket snapping. So off I go to the tool store and buy another socket. Before trying to loosen the bolt this time, I put the socket on it and tapped it repeatedly with a light hammer for a couple of minutes before attempting to losen it. This time when I applied pressure with my small breaker bar the bolt came loose with out too much fuss.

With all four bolts now loose I undid the two mounting bolts and removed the caliperfrom the bike. Got the caliper on the bench and removed the four bolts and seperated it. I used a pair of pliers to remove the pistons, I had a new set ready to install so I wasn't worried about damageing the old ones. To avoid damaging the cylinder I used a toothpick to remove the old seals. The dust seals looked old and battered the inner seals didn't look too bad, but I they are getting binned.

I gave the inside of the calper halves a good blast of brake cleaner and wiped them clean with kitchen towel. There was a bit of corrosion in the ring where the dust seal fits, this was cleaned out with a brass suede brush soaked in clean brake fluid. After another couple of sessions with the brake cleaner and kitchen towel, the new seals were then installed and the new pistons lubed with clean brake fluid before pushing them gently into place. The new seals that go between the two halves were fitted and then the caliper was bolted back together. I finished tightening the four bolts once the caliper was installed on the bike.

Once I had the brake pads reinstalled I opened the bleed nipple and used a piece of tube and a small funnel to pour brake fluid into the caliper through the hole where the brake hose fits. This made bleeding the brakes a much easier job. I had the brakes bled in five minutes, easiest brake bleed ever on this bike.

Had the bike out today for a wee hundred mile run on twisty roads, gentle on the way out and spirited on the way home. The brakes feel better than they have in a long time and there are no signs of fluid weeping around the caliper. So jobs a goodun.

Thanks again guys for your help and encoragement.

 

[Green Boy]

I appreciate that this is a fairly old post but I was talking to BMW spares who subsequently checked with 'BMW' who confirmed said that it's not possible to refurbish Tokico EVO front calipers and they don't supply any seals for this. In fact their suggestion was that if this ever became a problem that it would cost £300 plus labour per side to solve. When I asked them if they replaced any for owners, the chaps said "errr, no". So does anyone know if a replacement seal kit exists for these calipers? I know that Motorworks don't have them but I've seen James Sherlock sell a Tokico kit but not sure if it's for the EVO brakes.

Any thoughts much appreciated.