tr7triumph.com

I have had a spare set of 4 speed calipers (the small ones) on the shelf for a few years and went to rebuild them this weekend and found the caliper pistond wouldn't budge. I soaked them in Berrymans Chem dip for about a week and was easily able to get the bleed screw off but the pistons wouldn't budge. I then drove a wedge between the the pistons to see if they would move and they did after some pounding. Now the thing is, they won't come back out. Any way to get these babies moving outwards? As soon as I do, the pistons are getting canned and replaced with new ones so I'm not worried about banging them up.

Rblackadar

Have you tried compressed air?

Make sure that you have the piston facing the ground and up about an inch and a half off the floor. This way you should be able to pull it out with vise grips.

Dale
1974 TR6
1977 TR7 FHC

My experience is that compressed air up to 100 psi won't even look at them. Push them out hydraulically - that's how they are intended to work. You can simply fit it to the car -and press the brake pedal (after blee
ding out any air). If that doesn't work - I have used a grease gun in the past - obviously you need to make up a connection from grease gun end (mine is 3/8" UNF) to the brake pipe inlet which is 10 x 1 metric. Then just pump in grease and the pistons WILL move outwards. If one piston moves more than the other - clamp it so the other gets some exercise. Eventually both will be moving easily - pump until one of them pops out, and then hope you can wiggle the other one out too. The whole lot now needs careful cleaning to remove ALL the grease before re-assembly. Note the caliper pistons are same as Classic Mini (84 -2000) - and stainless pistons are readily available, which don't rust in future!