I'm replacing brake pads on my 1980, something I have done several times since I bought it in 1980. As we all know it is not the easiest thing to do, but it has never been overly difficult either. However, this time one of the one of the pistons is refusing to push back enough to get the get one of the pads in. What little it will move it does move it does so grudgingly, hanging up at various times. The calipers are stainless sleeved. The pads I'm replacing were not worn but I found they were cracking for some reason. So, the pistons would not have been overly extended.

Any thoughts on what might be causing this.

 

When is the last time you flushed the brake fluid?

Have you tried opening up the bleed port?

 

brake fluid about 5 years, I did try to push it with the bleed open.

 

Then time to pull the caliper off and remove the dust seals for a deeper dive.

 

Some of them look like this when you open them up: Water in the brake fluid does this. The air sneaks past the caliper seals, and the brake fluid absorbs the water like a magnet. Very frequently there is brake fluid past the dust seal, but outside of the caliper seal, where it should not be. This means the caliper seals are leaking ever so slightly. Even if you do not see it on the ground, yet. But apparently it is enough to let some moist humid air come in contact with the brake fluid.


This pair is obviously particularly bad. This set had to be pried out. Even the aluminum eventually corrodes. But the red goo is iron rust, from the iron calipers. Even when the bores are SS sleeved, there is still plenty of iron exposed to the brake fluid. So any moisture becomes a problem.



But once the deposits build up thick enough, the piston will **** and jam, as seen by the witness mark here. And the deposits did not look too bad even, in this set. Note that this is a S.S. sleeved caliper, so the sleeves do not prevent this corrosion.

I can not tell you how long it would take for moisture to sneak past the caliper seals, but it tends to happen faster the longer the car sits, and the seals are not exercised, so then they relax and leak. When the car and brakes are excercised at least monthly, there is a lot less trouble with these seals.

This simple couple dollar conductivity tester checks for water in your brake fluid. Every mechanic should have one. Normally I use it to check the master cylinder reservoir. But C3 calipers leak thru their seals, so I would squirt a little fluid out and check that, and see if it is time to flush. It measures 0 to 4% water with four lights.




All leaking, all had deposits.


A few months worth of cores. All leaking. And at least 80% of them had SS sleeves.

Keep that fluid clean!

 

I use one of those brake fluid moisture testers every day. Several times a day. And we sell a LOT of brake fluid flushes because of it.
Working on Harley Davidson motorcycles everyday for 50 plus years now. And we switched over from DOT 5 To DOT 4 About 20 years ago now. The difference in how often we rebuild master cylinders and calipers since the switch is astounding.
Let's just say I'm totally sold on DOT 5. But I'm just speaking from 50 years of being a professional mechanic.

 

I tried the DOT 5 in my brake system and it changed the feeling of the brake pedal when the fluid was cool. After warming up a bit the pedal felt better but still not quite the same as the DOT 3 fluid that I use.

After driving the car for several months with the DOT 5 fluid and I learned that in my 1968 C3 the older DOT 3 brake fluid made the brake pedal feel more "normal" to me. Either of them would allow me to lock up all four wheels but the DOT 5 seemed to need more effort to push the brakes.

Honestly the pedal feel of the DOT 3 Brake fluid was better for me and my C3. I then flushed the brakes and replaced the brake fluid with DOT 3 Brake Fluid.

Many people don't follow the regular maintenance schedule for the Corvette's Brake system. Me, I have a peppy 427 and I want to stop as fast as it can take off so I can be safe with the power.

I have power brakes in my C3 and all the caliper pistons were replaced with the O-ring seal pistons. Nothing unusual or out of place, just standard improved pistons and that is all with sleeved calipers.

Flushing the brake fluid is critical for a properly functioning brake system. I do it every five years and do it myself with my Phoenix Reverse Bleeding System as it allows me to do the work all by myself. I also lets me do it in a jiffy instead of taking hours and hours to do a simple job.

If you bleed the brakes as often as you should then you have no reason or need to buy a Brake Fluid tester.

I use only high quality brake fluid and I change it before it goes bad. Many vehicle dealerships use gadgets like that to generate more business, car dealerships do that as well to separate you from your hard earned cash....

 

What is high quality brake fluid using Dot3 Walmart pre stone ?

 

Did you mean Prestone?

 

Thanks all for the comments. It won't be the first time I've cleaned up a caliper. Frankly, the worst of it is getting them torqued back to 130 ft-lb. I don't have a large enough vise to hold it. I've noted some stating to do the final torque after they are mounted. But on my '80 there is not enough space to fit the socket over the bolts. So as I'm doing this, any real advantage to moving away from Dot 3. Car is driven less than 500 miles per year.

 

The real advantage? It doesn't absorb moisture. It doesn't attract moisture. When my original master cylinder failed back in the early-mid 90's. I switched the system over to DOT 5. I had the one original caliper fail recently. The other 3 were replaced back then. Other than that one original caliper failing about a year ago. No issues with my brakes whatsoever. And unlike Chris. I have never felt a difference. Nor has anyone else I ever talked to.
For seldom driven vehicles. It is the best. Unless you use CSSB parts that use cheap rubber.

 

To 4-vettes "Unless you use CSSB parts that use cheap rubber."

What is the issue specifically with CSSB? My recollection is that the rebuild kits I used were from CSSB several years ago.