Had a brake job several months ago, two new front calipers, pads, and bleeding of the system. Have driven the car ('72 Stingray 350) several times with no issues. Noticed a small leak at the rear lip of the master cylinder so I purchased a new cap and seal and that helped but didn't completely stop the leak.
Transported the car to North Carolina for the summer to cruise the mountains and all seemed well. Two days ago I noticed small puddles of brake fluid at all four wheels. Checked the master cylinder and saw signs of leaking again, and half of the fluid missing.
Refilled the MS checked wheels for damage and found nothing obvious.
Refilled the MS, reseated the MS cap and took a ride, Brakes worked for about two miles and again all four wheels were leaking again.
I always use Dot3 fluid, but not sure what the repair shop used (they said Dot3).
If the repair shop used the incorrect fluid, could that cause a deterioration of the caliper seals, or cause leaking?
I've dealt with a leaking caliper before but not all four at the same time. I can't work on the car in the mountains so I will transport it home for a more detailed examination.
Could the MS be faulty,ie too much pressure, or maybe the proportional valve stuck?
Anyone seen anything like this before?

 

Since the purpose of the proportioning valve is to reduce pressure to the rear wheels, I believe when it fails that you are more likely to have the rear wheels just lock up not leak.

I also thought when the Master cylinder fails or is failing, that there is a drop in pressure to the brakes not an increase.

Richard

 

I believe the 72's had a pressure balance switch, not a proportional valve. When you fill your MC, do you fill it to the brim? You shouldn't if you do. Whenever my calipers began to leak at the seals, I removed them and cleaned up the bore and checked the seals for nicks, etc. I've always had success in stopping the leak(s). If the car sits for long periods, it can start to leak.

 

I'm certainly not a brake expert but having relatively new calipers (less than 3 years, and a about the same for the master cylinder) but fluid leaking out of the MC (i never fill to the brim) and all calipers beginning to leak at the same time seems odd. I had new pads installed several months back and had no issues, but am wondering if an different fluid (consistency) would eventually cause the system to leak, or, if I'm having an excessive pressure issue....
Still analyzing the problem...

 

Some of this makes no sense. Why would fluid leak up and then out. There is no reason the MC should leak fluid out the cover unless you are compressing the calipers in or maybe somehow the fuild is being super heated causing expansion during driving.
Check to make sure none of your brakes or all of them are hanging up like you are pressing the pedal all the time. Look at the rotors for a blue coloring or that the car wants to stop on its own when coasting. Debris in or a stuck balance or proportioning valve could cause this.
Second check for newly routed brake lines near exhaust. When you had the brakes done did they change the hoses? Concerning your leaking at the calipers make sure they did NOT use brake pad glue or some sort of paste that keeps the pad stuck to the pistons. This causes the pistons to not freely move independent of each other on each side of the caliper.
Hope this helps. Just my $.02

 

If your car is leaking at all four corners, you should rebuild each caliper. Have the calipers ever been sleeved in stainless steel? If so, consider rebuilding all four wheels with O-ring pistons. If they have yet to be sleeved, consider swapping them out for a stainless steel set with O-rings. Jerry

 

Couple of thoughts:

Check the condition of the rim of the master. If it’s rusty and pitted, very hard to get a good seal. Overfilling will just make it worse.

If you’re getting leakage from each wheel, you’re probably getting air in the system too. You mention a leak after two miles but not if the brakes were still working.

Does the car sit for long periods of time without being used? This seems to cause brake seals to fail.

 

If a shop did the brakes, were they experienced with C3 brakes? Putting the pads into the calipers can **** the pistons which could damage the bore if they weren't paying attention. If they used DOT 3 or 4 that's fine.

 

Tnanks all, I am currently traveling and upon return I'll bleed everything and inspect the calipers to determine where the actual leaks are,
Again, thanks to all.
I'll let you know what I find....

 

Still investigating brake issues. My brakes ave never been great. A little mushy but did stop the car. Rode with a friend in his C3 and his brakes would STOP the car on a dime, as I would expect with four wheel disk brakes.
Am looking at the booster. the push rod length (not the correct length?) and checking that the brake pedal clevis pin is in the correct hole - one hole for disk, another for disk/drum).
may have a booster leak. we've replaced the master cylinder, front calipers and the car is back the the original mushy brakes.
Car has a mild cam and vacuum is just barely within requirements for the booster but should be ok. Will probably replace the booster so everything will be new and we'll see then how it works!

 

Found the problem. Apparently the previous owner(s) had an issue with the booster and instead of replacing it, they adjusted the pedal rod and pedal clevis pin to try and compensate for a booster leak. The brakes worked, but mushy, until the booster just couldn't handle the pressure any more.
Replaced the booster, and master cylinder (to a disk/disk MC), bled the system several times and now have the best brakes and pedal that i've ever had.. Happy camper!!!