I’ve read through this entire thread as I’m always interested to read about other guys problems and then the solutions in case I ever find myself in the same position. Although I can offer no advise( there are so many better brains on this site than mine) I wish you well and will follow along.
Do the pads pull back or just the pistons on low drag calipers. With the corvette master did you bleed front and back at the same time? I have dual Wilwood masters and I have to bleed front and back at the same time.
I believe the Master cylinder is the culprit . I am thinking that the Master is bypassing . even if you have a rock hard pedal on second pump but eventually pedal falls to floor ,in my opinion its the master.
Two different MCs, displaying the same symptoms? The pedal does not fall to the floor. My pressure gauges say 1000 psi front and 900 rear and hold when I push the pedal down hard with either master cylinder .
I'm going to ask a dumb question. Are you using a Ford type brake switch, and is it pointing up. When pointed up, it can trap air. If none of this applies, please disregard.
GOT IT! Don't know exactly what fixed it but I have the best brakes I have ever had in this car. I tore all the brake lines out of the car and replumbed everything. I re-routed them slightly differently. I turned the PV right side up. I replaced the RPV in the rear with a new one. I did not think that the front RPV was holding the 2#, so I replaced it also. I highly suspect that the front RPV was the problem all along. Bled it out and HOLY SHIT! Test drive proves it out! I don't know what fixed it, but I really don't care at this point. Thanks for all you guys help and interest.
Yeah! It is kind of a letdown. I know the golden rule of one change at a time, but I just decided that after 7 years of fighting basically the same problem, it was time to just start over. All new stuff. My 1926 Ford Model T is my DD. Sunshine, rain or snow. I have a couple other hot rods, but this is my favorite. I know a lot of you guys have seen it, but here it is again. It has better brakes now than when this pic was taken!!!!! Thanks again guys. This thread kept me motivated.
Congratulations! Now that its fixed I think the decent thing to do is to out all the old stuff back and recreate the problem and then solve it. We know the answer but not the method. We all need to know for when this crops up again. Enjoy the car ! Chris
Good news! Glad you got it working. Curious to know if that residual valve is defective. My curiosity would have me testing it to see. Now go drive that beautiful Hotrod
I have the Corvette 1" in it now. but I think I will change it back to the 7/8" for the reduced effort. I'm a glutton for punishment. I hope the problem does not rear its ugly head again.
I’m voting you had a high spot in your plumbing and never got sufficient “ speed “ on the brake fluid to push the air out, since you said you rerouted some lines. Bones
Congratulations! I've been lurking and hoping for a definite cause; there is a lot of info here and worth the trip.
Being the kind of guy who just can't leave things alone, after a pretty good test drive, I decided there was still a little tiny bit of air in there. I put the car on the lift, raised it up just like I always had done, nose down, just like it sits and took off the wheels to bleed again. Bled all 4. Shut the bleeders, filled the reservoirs and hit the pedal. CRAP! I lost everything. Back to the long soft pedal. Well hell, what did I do different?? Then I realized that I had the car nose up just a little bit when they bled out right. After the test drive, trying to improve it, I had bled it out a little nose down and got the long pedal. So I raised the nose a lot and bled again and the high hard pedal came back even better. I think Pist-n-Broke was the first to mention tilting the car very early in this thread along with several others. I had always heard of tilting the car but had never found it necessary. . I can guarantee tilting the car can be a thing when bleeding brakes. The moral of this story is... never too old to learn and quit being so hard headed and listen to people... sometimes. Anyway, I have great brakes now. Thanks again. Oh! And Boneyard51! There is your smoking gun.
Gets back to remembering Air will always rise when in fluid. Sometimes getting it around the corners so it can is the devil.
Good save! I'm curious to know the inclination of the master cylinder when the car is pitched as it was when the problem bleeding occurred, and also, for giggles, when the car is sitting normally on its wheels. Chris
I've found so called "gravity bleeding" useful sometimes, and for whatever reason sometimes the flow it just stops. Rapping on the lines along the length with a wrench or a screwdriver handle will get things moving again. I think somebody here mentioned that. The more sofa-sticated the brake system the more trouble it can be to get a good bleed it seems. Funny thing about brakes as important as they are, it seems to be one of those tasks always given to the "new guy". Let him deal with it. When I was in the .mil the official tool for bleeding aircraft brakes was a $35,000 pressurized hydraulic cart (I know it cost that much, because one of them had turned up "missing" against the commander's hand receipt for a while. He was Not Amused). But nobody hardly ever used those, at every unit I was ever at, and that was a lot, somebody in the toolroom always had bolted an old simple hydraulic hand pump to a plywood board and fitted braided hose to that. LOL. Your tax dollars at work.
It's funny. I took the Model T out for coffee this morning. I am so used to having to double pump the brakes that even though the brake system is working correctly now, I am still double pumping the pedal. It's just automatic! Old habits are hard to break.
It is odd for sure. Ground profile is related spring adjustment so you wouldn't think that angle would play into air movement with the fluid but it can and does at times. It's seems to be with a big Rubber Rake I find it showing up. Even with that 3" is about all the difference we are talking about. It seems hardly possible that little step could cause a problem, but it can. Odd as it is it don't cause an issue on all those jobs all the time. I have no idea what brings on these things. Probably why it is such a problem when it shows up. Really glad you got it sorted out, now you gotta retrain that right foot.
Yeah, last night I got curious about the heights of the various components in my brake system. I had never really paid any attention to it. So I had the car on the lift and took some measurements at ride height. The MC outlets are at 15" off the ground. The front caliper bleeders are at 14". The rear caliper bleeders are at 16". Just 1" above or below the MC to the calipers. Lines all run parallel to the frame. No humps or bumps. The only hump in the lines at all is over the center section of the rear end. I just couldn't imagine where air could be trapped. If I hadn't seen it I wouldn't have believed it. The air was trapped in the right front. Edit: I think every time I bleed brakes again on anything I am going to jack up the front and passenger sides, just as a matter of course!