Well, I bench-bled the new master cylinder thoroughly, installed it, and tried again. When my wife pressed the brake and released it, it took several seconds for the calipers to release the rotors. When I had her press and release it and I opened the bleeder screw, it released right away.
So it must be the flex hoses. Never had an issue with them right up to the moment of this brake job. It's not going to be easy to replace them, but I'm going to try, without damaging the rigid line. If I do, I have a brake flaring kit on order, should be here Tuesday.
Got the right flex hose off without damaging the rigid line. Installed the hose, got that side all back together.
Left side, the rigid nut started to unscrew from the flex hose, but the line was twisting with the nut. And the nut at the metering block end was so tight, I had to use a 15" copper pipe on top of the tubing wrench as a breaker bar. When I did, the line broke at that end. I had anticipated this and bought a 12" new pre-terminated rigid line. So I bent this into shape (complicated shape, has a small, small crease, so I might re-do this line) and connected it and the new flex hose. The flex hoses are Raybestos professional grade, made in USA from RockAuto.
One thing I noticed was that the right hose had brass ends, the left one, steel-colored.
I used new copper washers on the banjo bolts, topped off the master cylinder and stepped on the brake. No apparent leaks. So I had my wife operate the brake while I began bleeding. That's when the NEW problem showed up.
I have bubbling and hissing and fluid loss at the left banjo connection. I double-checked the orientation, put two more new washers in, cranked it tight. Same thing. I bled the right side, all was tight, good and dry. For the first time, both front hoses flowed the expected amount of fluid instead of a trickle.
I also checked the release of the pads, and when my wife let go of the brake pedal, both front calipers release immediately and I can turn the front wheels by hand right away. No more 3+ second delay in the caliper releasing. So I solved that problem. But now I have a new one.
Either the new left flex hose or the reman left caliper is defective, in that I don't have a flat, tight connection at the banjo bolt. I will have to replace one at a time to know which, before I can return any parts. So the car is still off the road for another week.
Unless there was an extremely apparent defect in the hose banjo or caliper mating surface I have found sometimes you just gotta crank the banjo bolt especially on these newer replacement hoses where there going cheaper by using steel instead of the softer brass that takes a seal much better.
Yes, and it's the same banjo bolt, so either the flex hose or the washers. I used a new set each time, and used a new set when I hooked up the new caliper to the old flex hose, and it didn't leak then.
Last ones I got were made in Mexico. Where did those come from? I didn't have any problem with the ones I got, but they went on my great niece's Pontiac. What a nightmare to work on. I don't recommend a 92 Grand Prix to anyone. Everything on that car is difficult to do.
New washers came packaged with the new flex hoses, and also with the reman calipers. At this point I'm not sure which were the leaky ones and which worked. The flex hoses are Raybestos Professional Grade, made in USA. The calipers were remans from Centric. No telling where the washers are from.
Bled all 4 wheels, and when I got to the left front, it started sputtering again, and inhaling air when the pedal was let up. ARRGGHH!
I replaced the aftermarket bolt with the OEM, torqued it down, leak gone. Bled it, and my wife said the brake was firm. Tested it, felt good. I then put the wheels back on, took out the jackstands, and started the car. The lifters rattled because it has sat for 2 months.
Got in, pressed the brake - to the floor. Sailed to the floor. Brake light on, almost no braking action.
I think there are only two possibilities here, since I replaced the master cylinder: Either the bench bleeding was inadequate, or the pushrod is not adjusted to match. If the latter, I'm going to re-install the original master cylinder. Either way, I have to bleed EVERYTHING all over again. UGH.
When I finished bleeding, I had to add a lot of fluid to the master cylinder. I foolishly bled two wheels in a row without topping the master cylinder. I suspect I let it get too low and sucked in some air. Today I'm too busy, but tomorrow I'm going to bleed the master cylinder and then all 4 wheels again. Too bad I put the front wheels back on, much easier to bleed with them out. It's as much effort to jack up and remove them as to just crawl behind and bleed in place.
Bled master cylinder in the car, with the tubing loops back into the reservoir. No bubbles at all. Reconnected lines. Pedal feels fairly firm with engine off, sinks right to the floor with engine running. Brake warning light on whenever ignition is on, whether or not I'm pressing the pedal.
Did the factory vacuum tests and they passed, so it appears the booster is good.
Unfortunately, I can't find the old master cylinder. Even though I intended to keep it, I must have tossed it out with some trash.
Someone wrote about adjusting pushrod length to resolve this problem. Whoever did, can you repost?
Any help here? The pedal is firm with engine off, but sinks right to the floor with engine running. Since I let the master cylinder run low during wheel bleeding, I bled it again, and have not yet re-bled the wheels. I hope to do so tonight. Does anyone have anything to offer on this condition?
Only 2 things can cause that. Either there is still a lot of air in the lines, or there is a leak... including a faulty seal in the MC.
Assuming your bleeding process was done so the fluid moved rapidly (to expel air bubbles in the circular section of the tubes), I would suspect a seal in the MC or an awful lot of air still in it.
I would only recommend opening one bleeder at a time when bleeding. You need as much velocity and volume displacement as possible per stroke of the brake pedal. It helps to have a vacuum tank on assist with bleeding so no air drawn back before the bleeder screw is closed, plus it helps by moving the fluid faster.
I don't think the pushrod is that far out of adjustment to cause the pedal to sink to the floor.
Last week, after installing the new flex hoses on the reman calipers, I still had a very slight fluid leak at the left banjo-caliper interface. It took 2 tries, changing out the new washers for two other new washers, then replacing the aftermarket banjo bolt with the original bolt (even though they were identical in dimensions). Finally sealed that leak last Friday night. After doing that, I bled all 4 wheels, the pedal was firm until I started the engine. I rolled it a few feet and confirmed that braking is weak.
It's a dual diagonal system, and I've been bleeding it RR, LR, RF, LF the usual order, since the FSM does not specify what order. To bleed the wheels, I rigged a hose from screw to a bucket of clean fluid, submerged, had my wife step on the brake all the way, then opened the screw, closed it after all flow stopped, then had her release the pedal. Repeated each wheel until only clean fluid came out. They all bled normally.
I bench-bled the new master cylinder the first time, with plugs in the ports, cylinder level in a vise and full of new fluid, and pressed the piston with a dowel about 1" slowly, and repeated until there were no more bubbles, and travel was reduced to 1/8" per the instructions. Then I installed it on the car and bled all wheels. Yesterday I bled it again on the car, using tubing fed back into the bottom of the reservoirs. It never showed a single bubble, just a tiny ripple across the fluid surface with each push of the brake pedal. I then reinstalled the output lines and the pedal was good with engine off and to the floor with engine running. I held off doing more bleeding, pending comments.
The RF rigid line is mounted high on the firewall, just about at master cylinder height, and my neighbor commented that it would likely trap air there and be hard to bleed. I think that may be the issue.
There are no fluid leaks at all now. I've pumped the pedal dozens of times with no change in fluid level, and nothing showing at any caliper or wheel cylinder, or anywhere on the tar.