I was installing new pads on the rear this evening and find that the rubber boot/cover which is on the caliper piston would not turn freely as I compressed the piston back into the caliper to obtain room for the new pad. I sprayed some lubricant on it and tried to work it around with my fingers to get it to turn but I could not get it to do so. The piston retracts as I turn in my C clamp which causes the piston to turn in a clockwise direction. Once the piston retracted the rubber boot was out of position and I could not get it back into position w/o turning the piston in a CCW direction which causes the piston to come back out. I even tried to get the piston to retract by pushing it straight in with a welding type c clamp which is kind of like a vise grip/c clamp but it would not retract by pushing it straight in.

This doesn't seem correct to me and I'm wondering if I need to rebuild the piston bc this boot is frozen. Other ones I've worked on before would move freely when turned.

Thanks in advance for your input.

 

When replacing brake pads you have to push the piston back into the caliper. On the front brakes a C-clamp is a good tool for the purpose. However, the rear brakes are different because they incorporate the hand brake mechanism. You should use a tool such as K-D #3163 Disk Brake Piston Tool. If you don't have this tool, you might get by with a pair of long-nosed pliers.

You may have done some harm by using a C-clamp because the clamp presses straight back and you should be turning the piston.

I think the boot is a separate problem. It's too bad the lubricant didn't do the trick. I think you don't have to rebuild the caliper now but will have to do it some day. A torn or distorted boot will let water get in and rust will develop. I believe the caliper will work but the part of the piston which is outside the caliper seal but under the damaged boot will develop rust "blisters". Consequently, next time you replace those pads the pistons will not retract... and if you force them back, they will tear the caliper seal to shreds.

Rear pads last for such a long time you may never have to face this problem.

 

Actually the C clamp turns the piston clockwise when it is being compressed. I noticed that the rear driver side brake pads were worn out and the rear passenger not even half way down. This indicates a malfunctioning caliper I think so I bought a rebuild kit today for about 22 bux. The passenger side is probably fine, but should I do them both together or does it not matter. The labor is not a biggie bc I have the car up on stands this week since I'm installing H&R's and isolators and boots. I'm going to clean and paint the calipers black also. I found out that my car and all Maximas built from around 92 up thru 9/94 have different (38mm) calipers than those after this date. Supposedly they got a little smaller in diameter after 9/94.

Anyone know if it's recommendable to prime the caliper before painting, I couldn't find any high temperature primer so I'm not sure if regular primer will work with high temp paint over it. Is engine enamel acceptable as a high temp paint, goes up to 500 degrees.

 

I painted mine with engine enamel, both color and clear, without primer. It's been 9 months and they still look great. I baked mine in a 225 deg. oven for an hour to harden the paint.

Of course, my wife's cooking tastes like Krylon! Seriously, to get rid of the smell, remove the parts then turn up the oven to 500 deg. for 30 minutes.

 

I took the rear right caliper apart today and other than a lot of rust build up around the recess where the rubber piston boot is located and a little light deposits on the od of the piston everything seems normal. I cleaned the piston with brake cleaner and the chromed surface looks fine, there isn't any scoring or scratches, so this is good. I wasn't able to get the inside of the piston assy apart bc it requires a special (very thin)retaining ring plier which is longer than the ones I have. I'm thinking that I'll just put it back together replacing the seals and boot that are apart now and leave the piston insides alone. The kit I purchased include these parts and it consists of a new retaining ring and a seal. What do you think?

I am also painting the caliper black now that it's off. I spent some time cleaning it with a brass wire brush cup on a 4" grinder and have gotten it pretty clean. Put a light first coat on before I quit today.

Is it advisable to drain all the brake fluid from all the lines and replace it with new fresh fluid?

 

If you have never changed the brake fluid, it is time. Brake fluid is hydroscopic, that is it absorbs moisture. The more moisture it picks up, the lower the boiling point. I would recommend Castrol LMA (low moisture absorbtion) DOT 4 brake fluid. A quart should be enough to do the whole system.

You are probably o.k. without doing a complete rebuild on the caliper. Post a pic when you've got them painted.

 

Sandblasting is the best "prep" but a wire brush will do a nice job.

 

I ended up taking both rear caliper pistons out, cleaning them and re-installing the same rubber boots I took off. When I was putting them back together I realized the repair kits I was sold were not the correct ones. All the seals and parts were just a tad larger than the ones I'd taken off. So I just cleaned the rubber boots really good and reinstalled them. I did notice some scoring in the same area on the inside of the caliper. Should have probably replaced them but decided not to at this time. Everything's back together and working very well. Installed Axis pads and painted the calipers black. Also put in Valvoline synthetic brake fluid. Brakes work well.

I didn't bake the painted calipers cause I didn't want to have a problem with the misses.

I don't think the scoring was due to my use of the c clamp bc I didn't use it on the right side and it was scored same as the left. It's about 2/3's way back into the wall. Guess I'll keep an eye out for a deal on some new calipers.

What do you guys think?

 

Is the scoring inside the hole for the piston? If so then keep a sharp eye on them for leaking seals.

 

I've never done the Nissan and probably never will, don't feel like monkeying around anymore. But in the old days I did do the pliers/c-clamp bit and changed disc pads and even installed the anti-groan shims without bleeding. One day I got too far ahead of myself and tried to help a friend and his Porsche, and ruined the caliper. Was a 4-piston sort that cost over $800 supposedly wholesale (from this wholesale Porsche place in Yonkers), ruined my day for sure.

 

The scoring was inside the bore of the caliper where the piston goes in. It is about 2/3's of the way back into the hole. I don't really understand the cause of this other than there was quite a bit of surface rust on the OD of the piston. I suspect that due to the high humidity here (I live in South FLA)there must've been a significant amount of moisture in the system and that may've caused this.

I'll keep an eye out for loss of brake fluid.