Saturday, July 21, 2012

Cleaning stuck brake pistons

The techniques and hints mentioned below may do harm to your and other people's life, health and property. Please do not follow my hints unless you understand what you are doing and consider yourself mechanically experienced. Make sure to follow your car manufacturer's service manual when working with your car.

I've noticed that wheel hubs of my Honda Stream car become quite hot while driving for ten minutes or longer. Thus I suspected there is a problem with brake pistons start to seize. The recommended fix is to get a new set of rubber parts (boots, seals) from the dealership and replace them all. However and did not have these at hand so I decided to get things apart to take a look.

I took off the wheel and dismounted brake cylinder. To see if the piston is moving I popped it out brake cylinder for 10mm by carefully pumping the brake pedal, then pushed piston into cylinder with a clamp. While tightening the clamp I could feel the seizure of the piston -- it did not moved freely back into cylinder.

It clearly needs to be reworked with all rubber parts replaced and lubed. But since I did not have the replacement parts I decided to just clean up the piston as an immediate measure. To get under piston's boot I used a thin screwdriver with blunt edges to raise the edges of the boot out of the deepening in the piston. Then popped piston out for another 10mm or so. Be careful not to pop piston out completely -- it is a grand hassle to get it back.

Now the most critical part of the piston is exposed and could be observed:


Looks frighteningly, huh? Well, it will look better once cleaned with brake fluid, polished with a fine sand paper and finally lubed with rubber grease. I've done a few popping-pushing cycles cleaning the debris and lubing the piston. Here's the same piston already in a somewhat better shape:


What is remained is to push it back into cylinder completely and assemble things back. Large enough clamp is a handy tool for pushing brake piston to working position:


Although this technique might help in a short term, it's not a substitute for proper brake system rework.

UPDATE:

It has not been easy to find an aftermarket replacement brake pistons for Honda Stream (first Gen). Finally, I *hope* (as I've not fitted them yet) I found a size-compatible pistons from the Danish company named Budweg, part number 235426. Honda part-number for this part is 45216-S5A-J01.


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