Brake calipers

I'm no expert on this but I read another post on here that said a special extractor tool was needed.

 

Try reading through this post http://ferrarichat.com/forum/showthread.php?p=136110337&highlight=brake+caliper#post136110337

You may have to page UP/Down for the info.

 

Graham,

If there are no responses by Monday, I'll check with my mechanic.

Dave

 

I remember mine didn't just push in by hand, had to give them a little whack then they went right in.

 

May be OK. Won't know until you put pressure on pistons. Got to get fluid on seals to really know. Dry seals don't move hardly at all. Getting pistons in the first time requires some oomph. Under normal operation, pistons move very easily. If all you did was clean things up and put in new seals from a reliable source, put it back together and try it. If brakes release after application, pistons move just fine. If brakes drag, you have a problem.

John

 

If you are referring to inserting the piston after everything is clean, lightly sanded or hones, and with new rubber cylinder-wall flat o-ring seal lubricated with brake fluid or silicone, then the "tightness" you are experiencing is likely the piston having to compress the bore o-ring to slide past it. This is normal.

The piston, without the rubber seal in the bore, should like smoothly in the bore when lubricated. It should not rock. One test would be to "blow" out the piston, gently probe and remove the new rectangular section o-ring seal from the bore, and slide the piston in the cylinder to see how it moves.

The outer seals are simply dust covers and will have no bearing on the movement of the piston in the bore.

Jim S.

 

Graham - If they start all the way inserted, that is, with the piston face flush with the caliper, and then only move 2-3 mm, something is constraining them. When applying significant air pressure, the piston should pop out. The dust shield should not push it back in...not enough force generated by the dust shield rubber memory. Stated differently, how would you remove the piston at this point? Doesn't sound like you can if you are applying 150 psi and they do not come out on their own.

I assume that you applied the dust shield and its retaining clip after the piston was completely inserted. Is it possible that some of the dust shield rubber got wedged between the piston and the bore? Perhaps the rectangular o-ring in the bore groove (seat) rolled as the piston was first perusaded by it with the mallet.

In any event, I would remove the dust shield and its clip, and see if you can move the piston all the way out with air pressure. Perhaps it is binding owing to being askew when inserted? Are both pistons like this?

Jim S.

 

Graham - another thougth (please read my earlier post).

I can envision a scenario where the piston slices a crescent of the bore rectangular-section o-ring when first inserted. If a sharp leading edge of the piston "grabs" the o-ring as it is inserted, and you gently strike it with the mallet, it could have cut off a crescent of rubber that is now wedged between the piston and bore. Just another silly thought.

Jim S.

 

I popped out toublesome brake caliper pistons with a grease gun hooked to the brake fluid inlet line. Creates quite a mess when you are through but gets them out in a slow controlled manner. I did this on a MGA Twin Cam not a Dino but still it should work if all else fails.

 

When I would rebuild calipers I would clean the pistons with 600 grit paper soaked in brake fluid. I would do this to make sure that there is no residue on the pistons that would damage the new seal. I would then clean off the piston with a good parts cleaner. CRC makes a good brake cleaner which will work fine.

Clean the caliper housing. Install the new piston o-ring. Lube the exposed surface of the o-ring with brake fluid. NOTE: If you lube the whole o-ring and then install it in the caliper it may roll in the groove while inserting the piston.

Lube the piston with brake fluid and gently push the piston in by hand making sure NOT to have the piston lean to one side. After the piston is seated in the caliper you can install the dust boot. Some models the dust boot goes on first.

Install the caliper with the brake pads on the rotor. Push the piston to the pads to remove play. Install brake line and bleed.

NOTE: If you install the caliper and bleed the system. You may have play in the brakes. I had an occasion once when I rebuilt a set of calipers I had a spongy brake pedal. I found that the piston was being pulled back in the caliper by a tight seal when I let off the brakes. I lost brake pedal travel just getting the piston to the pad.

YES A NEW SEAL CAN MAKE A PISTON FEEL TIGHT. THE SEAL IS AN INTERFERENCE FIT. THE SEAL ID IS SMALLER THAN THE PISTON. IF IT DOESN'T LEAK OR PULL THE PISTON BACK YOU'RE DONE. IN EITHER CASE YOU'LL KNOW.

IF BOTH SIDES FEEL THE SAME I WOULD RULE OUT OPERATOR ERROR. IN ANY CASE YOU TAKE THEM APART TO INSPECT THEM AND IT WON'T TAKE THAT MUCH TIME TO PUT IT BACK TOGETHER.

 

Thanks for the update. Good to know if suggestions work. I have never used anything other than brake fluid as a lubricant so never had the problem. Looks like mixing lubes might have done it. Now we all know. Brake fluid only!

John

 

I bought a set of these and they make one person brake bleeding a quick and easy task.
Bleeder screws with a check ball in them:
http://www.speedbleeder.com/