My hydroboost on my 1976 Biarritz with 9000 original miles was rebuilt because it was leaking.The brakes were working fine and just had the leak. When the mechanic reinstalled it he did not flush and bleed the power steering system; replace the fluid or change the p/s filter. The booster was completely rebuilt and tested before it was shipped. The booster failed and the brake pedal would not come back up. It was sent back to the rebuilder who said the spooler valve seized. When it was disassembled he found decomposed rubber mixed with sludge between the lands of the spooler valve and explained this was an impediment to the free movement of the valve and caused the pedal delay. It is my understanding that the power steering system should be flushed and bled and the p/s filter changed when taking out and reinstalling the booster because you are disturbing the system and sediment can get stirred up and the first part of the booster to be affected would be the spooler valve. The mechanic said it is impossible for a 9000 mile car ( mind you it is 47 years old ) to have sediment in the power steering system and it is not necessary to flush, bleed and change the p/s filter when r/r the booster and the fact that it was working before it was sent for a complete rebuild proved there was no sediment in the power steering system. The mechanic was also not aware there was a power steering filter. Am I wrong?
The rubber likely came from a internal failure that is starting of a hose so I would think you would want to replace the hoses before you put it back together or you will be doing it all again.
Sounds like the mechanic is just making stuff up to try and shift the blame for either not doing a flush or not recommending it be done.
Someone else would have to confirm but I don't think a 76 would have had a filter. I don't think its very common to have filters, I have worked on a lot of stuff with hydroboosts and never seen a factory filter. Cadillac used em in the later 80's some models. The hydroboost came out in 74 so it was fairly new so maybe they were being safe?
Filters on a hydraulic system are usually on the suction side of the pump. You can't really have one on the high pressure side. You also have to be very careful to put one on the return side but that is where Cadillac did it in the 80's. If it was to clog and doesn't have some fancy bypass system it could turn what was supposed to be a low pressure side of the system into high pressure. They would have had to design a different pump and reservoir system to put a filter on the suction side.
Sorry for bumping an old threat but I have a similar issue with my 76 Eldorado. The rear brake lines were disconnected. When the mechanic reconnected them and pressed the brake pedal, it won't come back up. Prior to this, the brake pedal worked fine with only the front brakes connected. Mechanic said it probably needs a new Hydrobooster.
Did you end up fixing your problem Mike and how did you do it?
Thanks,
Rafael
Mike was logged into the forum as recently a month ago but this was his last post. Perhaps he will be back on soon and can let us know what was found.
I'm not sure whats going on with yours. Did your mechanic try plugging the back again to see if that magically fixed it? I probably would have tried that just to see.
The usual issue with this style of rear caliper is related to the integral parking brake. The other method of rear discs is to put a drum brake in the center of the rotor. With this style the parking brake is a ratcheting screw mechanism that threads into the piston. Its a lot of moving parts in a hostile environment plus it ads a new place to leak or contamination so they often get stuck. Its not like disconnecting the hydraulic lines would unstick them so I'm not sure what the logic was behind that.
I will have to keep thinking about how lack of resistance because they were not yet bleed in the rear could effect the booster. I suppose if it was old and tired and the pedal just had not been pressed that far in a long time what ever was left of some seal or ring just let go?
The '76 system does have a filter. It is located right at the P/S pump. Anyone that thinks there is no sediment in the system may be incorrect. Inside the pump housing, affixed to the pump itself is a magnate about 1" in diameter. It picks up any larger silt that the filter may not trap or from any fluid that doesn't make it into the system.
Flushing the entire system is very easy. Remove the return line from the cooler that runs along the bottom of the radiator, plug the open end and place a section of hose into a gallon jug. After draining the majority of the fluid, refill the system and run it at an idle while adding new fluid to the reservoir. When the fluid comes out clean, put it back together and top it off.