Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hello, My name is ***** ***** I'm here to assist you. The rear reservoir(closest to firewall) is for the front brakes. It is not uncommon to get some fluid movement(a stream) from the reservoir when applying the brakes. If you are getting bubbles, then you have air in the front brake fluid circuit.
Are you getting a red brake light and no pedal? Have there been any recent repairs before the problem started? What year is the truck? (it says pre-1983)
I had an '80 Big 10 that would get intermittently a spongy pedal. I would bleed the rear brakes and it would be fine for a couple years, although I never got a large volume of fluid during the bleed. I suspected air was entering the system through the aftermarket wheel cylinders intermittantly. Is the pedal low, in addition to no pressure to the rear brakes. Are the shoes physically not applying?
The proportion valve can stick, but will usually cause the red brake light to come on, unless it has been unplugged at the valve. The valve is located on the driver's side front frame rail near the gear box. Sometimes tapping the valve will unstick it. It used to be a discontinued part, but may be available from restoration companies now.
Have you bled the system at the master cylinder? That would verify you are getting pressure out of the master cylinder. Should be getting a good stream from both lines when holding pedal and cracking line. The smaller front reservoir is for the rears. I have seen new parts not function properly(especially master cylinders) so don't rule that option out.
It is a common issue with the valve. It may need a different valve to compensate for the disc swap, also.
Please take the time to rate my service and feel free to let me know if you need any further assistance. Thank you, George