adelane

Hello,


I have a 86 transam, with hydroboost, SSBC 1LE front brakes, rear standard disc brakes, 4th gen master cylinder, new hoses...



Everything worked fine for a lot of miles, about 2 years....


But today, when I pushed really hard the brakes, the warning brake light came on the dash.



And now it comes on everytime I brake... it goes off everytime I release the brake pedal !



I never had this problem before... If it would stay on, I would understand a proportionning valve problem.



The car stops good, but this light fears me...


There is not any leak in the system.


Thanks For your help !


Adelane

W.E.G.

Your combination/proportioning valve has shifted just enough that the valve activates the warning switch when pressure is applied to the braking system.

I recommend that you first bleed the entire system. There is some chance that bleeding the system may put the problem to rest. In any event, my opinion is that bleeding the system is the first thing you do when hydraulic issues appear.

Once the system is bled, and all air is eliminated from the lines, you need to reset the combination/proportioning valve. Folks have different ideas on how this is best acccomplished. One good way of doing it is posted at https://www.stevesnovasite.com/forum...12&postcount=4

adelane

Hello,


Thanks for your answer.


I've just bled every wheel, begin with the rear right, rear left, front right then front left... I did this circle twice.


I've used half a quater of DOT3 fluid.


Then I started the car and had the same problem. If I press the pedal really firmly the brake warning lights on, as I release the pedal just a few the warning light goes off...


I don't really understand the procedure to reset the valve... how could I bleed the front and the rear together ?


Thanks for your help


Marc

//<86TA>\\

iTrader: (14)

The reset involves just standing on the brake pedal as hard as you can and it will reset, provided the system can make enough pressure to do so(no air, leaks ect)

adelane

Hello,


After testing everything, bleeding, standing on the pedal...


I think it may come from my rear brakes.


When I don't apply the brakes, the rear discs are really loose, comparing to the front one...
My mistake is that I never use my e-brake...


I tried to apply e-brake about one hundred times to auto-adjust the calipers, but it didn't work !


Have you another solution ?


Should I upgrade my rear calipers to another model to secure this ?


Thanks for your help



Marc

Drew

iTrader: (58)

The light comes on when there's a pressure imbalance between the front and rear brake circuits. If other words, you have air or a blockage in the hydraulic system. You should be looking for leaks, bad seals around the pistons, rotten hoses, etc. You might need to bench bleed the master cylinder to get all the air out of it.

One place these cars really like to have issues is the passages inside the brake hoses where the metal end fitting meets the caliper or hard line. That tiny passage rusts from the brake fluid not being changed frequently enough, and then the rust and garbage in the brake fluid will act like a check valve, allowing fluid to flow one way, but not the other, or blocking the hose completely. When that happens, the caliper won't grab at all, or it'll grab and won't release.

I don't think you can have the calipers far enough out of adjustment to cause the light to come on. Much more likely the problem is one of the issues I listed above.

adelane

Hello,


I've just passed some time to investigate on my car regarding your coments.


No leak, no liquid was missing when the problem began.
I've bled everything, removing the master cylinder and bench bleeding it, bleeding the 4 wheels after...


The lines are not rusted, liquid was clear... No obstruction when bleeding the wheels.


the 4 calipers grab and release, I just checked.


I have one millimeter of gap on the rear calipers when released, they don't want to adjust... I don't reach to do it !


Thanks for your help

Marc

Bob88GTA

iTrader: (2)

Marc,
Take the rear calipers and rotors off and put the rotor in a vise to hold it. Take the nut off the ebrake arm, rotate the arm until the pads are against the rotor, re-position the ebrake arm to resting position. WITHOUT MOVING ANYTHING, remove entire assembly from vise and reinstall on car. Bleed the breaks. You should now have ebrake funtion, AND no gap between rotor and pads. I done this, it works like a champ.
As far as the resetting of the light, 86TA is correct.
Drew is also correct on the deteriorating hoses and other issues.