Oldsmobile/Buick Repair/77 corvette
QUESTION: I have replaced just about everything in the brake system. Power booster was bad, replaced that and the master cylinder along with both front calipers, and the rear wheel cylinders as well as a bad RR brake line.
I bled everything and still have not much pedal. The fronts bleed strong, but the rears are not strong and the pedal does not fade when I open the bleeder valve. I get some fluid out of the rears, but not strong.
I beleive I have a proportional valve problem. I opened the front caliper and pushed on the the pedal, but it did not reset.
How can I reset the proportional valve?
ANSWER: HI GREG,I AM VERY SORRY THIS HAS TAKEN ME SO LONG TO GET TO YOUR QUESTION, I JUST NOW RECEIVED
THIS AT 7:15.. ??? WELL I THINK YOU KNOW WHAT YOU ARE DOING BY THE SOUNDS OF THINGS SO I WILL GET TO THE POINT, DID YOU BENCH BLEED THE MASTER CYLINDER. IF NOT I WOULD DO SO..MAKE SURE AFTER THAT THERE IS A GOOD FLOW OF FLUID FROM BOTH SECTIONS OF THE MASTER. THE WAY THESE MOUNT ON THE BOOSTER [POINTING UPWARDS,TRAPS AIR.]AFTER YOU DO THIS PUT IT BACK ON THE CAR AND BLEED THE LINES GOING INTO THE MASTER. ONCE GOOD,CRACK THE LINE GOING TO THE PROPORTIONING VALVE,PRESSURE SIDE. BLEED THE LINE HERE..IF GOOD FLOW IS TO THIS POINT NOW GO TO THE OUTBOARD SIDE OF THE VALVE,BLEED THE SAME WAY..IF LOW PRESSURE AND VOLUME THIS IS MORE THEN LIKELY YOUR FAULT..SOMETIMES ON THESE OLD CAR YOU CAN NOT RESET THEM.WHAT YOU HAVE DONE IS CORRECT..MAY NEED TO REPLACE..BUT LETS SAY THE FLUID IS GOOD GOING OUT, THEN REMOVE THE LINE ON THE AXLE AFTER THE RUBBER FLEX AXLE HOSE AND BLEED HERE. WE HAVE SEEN MANY OF THESE LINES COLLAPSE, CAUSING YOUR PROBLEM...IF FLUID IS STRONG TO THIS POINT THE ONLY THING LEFT IS FAULTY WHEEL CYLINDERS...LET ME KNOW HOW THIS GOES.GOOD LUCK,,TOM..
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QUESTION: Thanks Tom. I did bench bleed the master cylinder. How do I bleed the lines going into the master?
I have the two lines from the master that go into the proportional valve. Are these the ones that I crack open?
There is more to the story. I was given the wrong brake shoes and the wheel cylinders overstroked and popped out during the test drive. After that I had pedal. But when I replaced the shoes and the wheel cylinders I had no pedal. I believe the p valve is good. What if I open both rears and push the pedal to reset? Or the fronts?
I have not bled the p valve so I will try that.
ANSWER: HI GREGG,TO BLEED THE MASTER,JUST CRACK ONE LINE AT A TIME AND HAVE SOMEONE PUSH DOWN ON THE PEDAL LIKE YOU WOULD BLEED THE BRAKES.SO CRACK ONE LINE LOOSE AND TIGHTEN AND LIFT THE PEDAL DO THIS FOUR TIMES OR SO..YOU WANT A GOOD STEADY FLOW OF FLUID..DO THIS AT ALL THE REAR SECTIONS AS WELL..AS LONG AS YOU ARE GETTING A GOOD AMOUNT OF FLUID AND PRESSURE OUT OF THE REAR WHEL CYLINDERS THEY ARE OK..I THINK YOU JUST HAVE NOT BLED THE REAR SECTION OF LINE GOOD ENOUGH TO REMOVE ALL OF THE AIR...THIS MAY TAKE ABOUT 20 TO 30 TIMES OF UP DOWN-- UP DOWN.ONCE YOU HAVE ENOUGH PRESSURE TO THE REAR SECTION,, THE P VALVE WILL BE OK [I BET].LET ME KNOW HOW THIS WORKS FOR YOU..TOM
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QUESTION: Tom: I am working on a '77 corvette that might not be starting because of the clutch safety switch located on the clutch pedal. I tried to look under there and cannot see the switch due to the AC duct. Do I need to take all this off or can I go upstream and test the purple and purple and white wires somewhere with easier access???
HI GREGG, THE CLUTCH INHIBITOR SWITCH IS ON THE CLUTCH PEDAL,LOOK AT THE PEDAL PIVOT AND YOU SHOULD SEE A SWITCH BY THE ANCHOR. REMOVE THIS PLUG HARNESS AND JUMP IT TOGETHER THIS WAY YOU ARE BY-PASSING THE SWITCH..SEE IF IT WILL CRANK OVER LIKE THIS,IF SO THE SWITCH IS BAD..IF NOT CK FOR POWER ON THE PURPLE WIRE ON THE STARTER SOLENOID WHILE SOMEONE IS HOLDING THE KEY TO THE CRANK SIDE OF THE IGNITION..SHOULD HAVE POWER HERE ON THIS WIRE,IF SO THE STARTER IS BAD AS LONG AS THERE IS BATTERY VOLTAGE TO THE BIG WIRE AT THE STARTER SOLENOID. IF NO POWER TO THE SMALL PURPLE WIRE WHILE CRANKING THIS OVER YOU HAVE A PROBLEM WITH THE WIRING OR IGN SWITCH..CK THIS OUT AND GET BACK TO ME IF YOU NEED MORE INFO,,TOM..