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Hi All, thanks again for all the help, I just received new brake lines and calipers. Does anyone recommend adding thread sealer to lines?
Nope.
On the bleeder valves only, and only on the threaded part, if you are going to vacuum bleed them (not recommended, as air can be pulled past the lip seals, if equipped).
On the lines, the seal is on the flare face to tapered seat. So thread sealant does nothing to actually seal anything, but can interfere with the actual seal.
What type of brake fluid. Synthetic can be spongy. I changed from dot 5 to 3 and no more spongy feel.
What brand fluid did you use? Im currently having the same problem with my 81'. All the calipers and line has been replaced but my brakes are still spongy and low. My "check brake light" is on.
Hi, I used multiple venders for my parts listed below. With that said, I replaced everything I possibly could except for the main lines. After several times bleeding, test drives, bleeding again, pressure testing all the lines several times, and repeating bleeds. The play in the pedal is still more than I like, the pedal still stops about 2in from the fire wall but does stop and will lock up. After all the great information/help I received from the Forum and from local corvette shops this is the best I can get. To get the performance I am really looking for I would need to change the entire system with a Wilwood system. Good luck and hope you get better results.
My car is right where yours is at. About 2" from the fire wall will stop and will lock up. i read on another thread talking about a brake proportion valve being clogged!?
When you are driving the car, does pumping the brake pedal at application make a difference? Used to have a '73 with manual brakes and a low pedal. For a while I would press the brake pedal early just to seat the pads, then release and press again for actual braking -- brought the pedal up and increased firmness significantly. Final fix for me was using the Motive pressure bleeder but in reverse. Removed some fluid from the master, fitted the reservoir output hose to each bleed screw in turn, then pushed fluid from the bleed through the caliper and lines, etc, till it came up through the master. Some sealant on the bleed screw threads was definitely required.
The "proportioning" valve is actually a brake pressure differential safety switch, not a proportioning valve, most c3s do not have a proportioning valve. IIRC the later ones may have a "combination" valve that does both functions.
In either case the piston inside shifts if the pressure in front or back is different and turns the "brake" light on. And shuts off fluid to one end of the system.
If so it needs to be re-centered after bleeding your brakes.
Or use this $7 tool to keep it from moving in the first place: The tool threads into place after you remove the elec switch.
