Morning all, I just replaced the brake hoses, brake booster on my 69 GS California. Was able to get the front brakes to bleed out without issue (clean fluid to the calipers). Yesterday I did the rear hose above the rear end. Now the problem started. I went to the pass side rear and hooked up the mity-vac, pumped it up to get vacuum and had bubbles before I cracked open the bleeder. Bad seal, right??? So I went to driver's side rear, same thing. Got a new pump and fittings, still the same issue. Not moving fluid to the rear brakes. I verified that the master is moving fluid. (removed and cleaned, inspected and bled on the bench.) Only thing left is the prop valve. Been searching for the symptoms on a bad proportioning valve. It would seem that this is the most likely suspect now. Lines are stainless steel front to rear, rear axle and feeds to the front wheels. Soft lines are new Russel braided lines. Any ideas on what the issue is????? Jimmy 1969 GS California LS1/4L60E/3.31 posi Formerly Stage 1 455, TH400 - (Muncie M20 (Stage 1 ate it!)) Went from 9 MPG to 20 MPG - would like to drive it before the snow flys.
Your distribution block, is it just a distribution block or is it an all-in-one combination valve? There is a piston that moves to block off fluid to the front or rear if you loose pressure on one side. It sometimes has to be re-centered. If there is a rubber nipple on the front, push it release the valve.
I had a heck of a hard time getting the brakes on the RaSabre to bleed once all the parts were replaced. as a last ditch effort I made a power bleeder that pulled fluid through the system and into a neg pressurized canister. I could stand up front and pourfluid into the master and watch it as it was pulled through into the resivour. Worked like a charm .
Before we start condemning parts, find out where in the system your losing pressure. Start at the master- if you crack the line off the master, is there pressure there? If so move further down the line. Or work backwards from the wheel cylinders. Do you get pressure from the fitting going INTO the rear hose? Pressure out from the other side? If the master has some age on it, they tend to go bad during the bleeding process because you push the seals past thier normal travel. Your new rear hose could be bad too. Never discount the fact a new part could be bad. Especially in this day and age.
I had the same issue when I changed my front calipers on my 69 Skylark. As mentioned above the proportion valve closed up not allowing any fluid to the front lines. I used the plastic brake bleeder tool that screws into the top of the valve, but you have to remove the fitting that the brake light switch attaches to.
OK, I will be pulling the driver side header tonight to get access to the block. Then I won't be talkin out my azz. Anyway, when I built the car in 1997 I used a disc brake set-up from a 1972 Olds 442. I did not change out the block (1968/69 Special). Everything was fine for years. Then the brake pedal got "hard" and difficult to stop. Started with calipers and pads, everything is fine, no change in pedal. Figured that the lines had gotten swelled after 30+ years as they lost some flexibility. So I changed out the fronts and noted that the pedal was worse, then the rear line. No change and still difficult to stop. Then did the master as if was last serviced in 2005. The Brake Best master I got was bad right out of the box. bench bled and all bubbles out, installed and found it pushing air in the rear well. At that point I cleaned out the original (see 1st post). Front well pushes all kinds of fluid, no bubbles. Rear well also shows fluid movement & no bubbles. So now I'm down to the really old block. Once I get this changed I will be doing the 2 man bleed and see what we get.
Just buttoned everything up.....still no brakes. All I can figure is the master must be bypassing internally. It moves fluid ok, but will not stop the car. Going to pick up a different master in the morning
Finally got back on the car. Vehicle is a 1969 GS California that I installed PDB from a 1972 442 on it. I did so using the 70-72 Power Master Cylinder. It worked until this summer (15 or so years). Always had a situation were the pedal dropped to the halfway point but had brakes. More research revealed that the 67-69 system used a different master, Corvette style, with 2 bail clips. This also only is using a distribution block and does not have a prop valve by the master (early style). So far I have replaced: Booster, Master, lines to dist block, Distribution block, hoses, wheel cylinders, brake pads. So the system is brand new and flows hydraulic fluid. I have never adjusted the brake pedal rod. The early master has a deep well recess in the plunger, but the 70-72 master has the shallow version. Pedal feel is the same. Have checked all connections for leaks and everything is good. There are 2 different lengths on the push rod, 2 .375 or 4.12 I think that is the difference in cup depth as far as the rod is concerned. Is this something that should go to a shop to get power bled and adjusted? I am kinda at the end here. Jimmy
Sounds easy and both stupid. It worked for me in the past while replacing every hydraulic part in a restoration. This was suggested to me buy people in the know. Fill the reservoir open the back two bleeders, jack up the front of the vehicle. And let it sit overnight. Maybe check on on fluid once in a while, and refill if needed. Next day bleed as normal.
A couple of things you can try. Try using a vacuum bleeder pump to pull the fluid. Better is to use a pressure bleeder if you can get access of one.
My 2 cents. I had exactly the same issue after a complete brake system replacement (part of a restoration) on a 1977 Chevy K10. All GM vehicles of the era use essentially the same technology in the prop valve. As already mentioned by knucklebusted, the likely issue is the prop valve has move off center and is blocking fluid to the rear outlet. You must re-center the valve and then install the tool below while you bleed the rear. The tool screws in where the brake pressure sensor/terminal goes.
Hey, I did figure out whats going on. Had a fitting at the master to intake go bad. Found it to be loose. Tightened everything up and had good brakes again. Then I had a valve spring fail...... cars! All re-rebuilt again and finshing up the wintertime projects
That's the only thing I can think of. But that doesn't seem like it would cause a bleeding issue. They are two separate closed systems. At first I was thinking is was the M/C piston, sometimes the bore is not perfect and it bleeds by the o-ring, but that didn't seem to be the issue from what I was reading. It happened to me once and when I was pressing on the pedal, it was okay and if I pressed too hard it broke loose right to the floor.
agree - I was thinking of a possible fitting. Maybe his brakes were not working due to a lack of vacuum? Maybe the OP can update us.
I had this problem with my ‘72, I went back and forth 10-15 times, turned out I had replaced the calipers and the bleed valve was over twice as long as the original, I had to turn it out about 3/4 inch to get it to work, it was affecting the back brakes bleeding correctly because I was not getting the air out of the front because of this.
