Volvo Owners Club Forum - View Single Post - Advice please, 245 master cylinder and brake calipers

Clifford Pope · Jun 27th, 2022, 08:02

FWIW:

I've done this many times, and I usually find in pre-checking for the MOT that one or more of the rear pistons are stuck or sluggish.

My method

Jack up and remove wheel, remove springy cover exposing the pads, and make sure that you can lever each one back into the caliper. I use a G-clamp between the protruding pad and the end of the caliper body.

When you find one (there are 4 in total) that is stuck, pull the pad out and use a wedge lever of some sort between the disk and the piston. With a suitable lever you can force it to retract. Run a few drops of brake fluid round the edge.
You can apply considerable force here if necessary. I have never yet found a piston that would not move in the end, and never had any problem with damaging either disk or piston by doing this.
Push the piston right in, then pop a worn out pad (ie something thin) into the space, and apply the brakes to force the piston out again. This may need you to stand on the brake pedal, especially if the booster assistance is unavailable.
Inspect the caliper again, run a bit more brake fluid round, and lever the piston back in again. Go on repeating this as many times as it takes to free it up (put the spacer in to stop the piston coming out too far).

Then move on to the next piston/caliper.
As I say, I have never yet had to give up. ALL pistons free up in the end.

Points for extreme CAUTION if you really do want to remove a caliper.
There are only two bolts, but they are VERY tight and probably locked with adhesive too. It is very easy to round the heads of the bolts. I don't know what you do if it becomes impossible to extract a bolt. The nearest I have come to reaching that point is when I once had to hammer on an old socket that was too small and then use 2 yards of scaffold pipe to shift. It broke the socket lever first time.

Take extreme care to free off brake nipples very very carefully if you need to bleed the brakes. They snap off very easily. My infallible method is to run a few drops of brake fluid round, put a tight fitting ring spanner on the nipple, apply a small amount of force, AT THE SAME TIME hitting the nipple END_ON with a hammer with quite a lot of force. NOT sideways - it will snap off.
Apply more fluid, and work the nipple backwards and forwards to ease it out gradually.

Likewise be very careful undoing brake pipes. Hitting the union sideways on to squeeze the hexagon can work, if you can insert a very heavy block of steel or heavy hammer behind on the other side to avoid straining the pipe.

Jun 27th, 2022, 08:02	#6
Clifford Pope Not an expert but ... Last Online: Yesterday 12:45 Join Date: Dec 2001 Location: Boncath	FWIW: I've done this many times, and I usually find in pre-checking for the MOT that one or more of the rear pistons are stuck or sluggish. My method Jack up and remove wheel, remove springy cover exposing the pads, and make sure that you can lever each one back into the caliper. I use a G-clamp between the protruding pad and the end of the caliper body. When you find one (there are 4 in total) that is stuck, pull the pad out and use a wedge lever of some sort between the disk and the piston. With a suitable lever you can force it to retract. Run a few drops of brake fluid round the edge. You can apply considerable force here if necessary. I have never yet found a piston that would not move in the end, and never had any problem with damaging either disk or piston by doing this. Push the piston right in, then pop a worn out pad (ie something thin) into the space, and apply the brakes to force the piston out again. This may need you to stand on the brake pedal, especially if the booster assistance is unavailable. Inspect the caliper again, run a bit more brake fluid round, and lever the piston back in again. Go on repeating this as many times as it takes to free it up (put the spacer in to stop the piston coming out too far). Then move on to the next piston/caliper. As I say, I have never yet had to give up. ALL pistons free up in the end. Points for extreme CAUTION if you really do want to remove a caliper. There are only two bolts, but they are VERY tight and probably locked with adhesive too. It is very easy to round the heads of the bolts. I don't know what you do if it becomes impossible to extract a bolt. The nearest I have come to reaching that point is when I once had to hammer on an old socket that was too small and then use 2 yards of scaffold pipe to shift. It broke the socket lever first time. Take extreme care to free off brake nipples very very carefully if you need to bleed the brakes. They snap off very easily. My infallible method is to run a few drops of brake fluid round, put a tight fitting ring spanner on the nipple, apply a small amount of force, AT THE SAME TIME hitting the nipple END_ON with a hammer with quite a lot of force. NOT sideways - it will snap off. Apply more fluid, and work the nipple backwards and forwards to ease it out gradually. Likewise be very careful undoing brake pipes. Hitting the union sideways on to squeeze the hexagon can work, if you can insert a very heavy block of steel or heavy hammer behind on the other side to avoid straining the pipe.