1980 Plymouth Horizon Bleeding Brakes

BUYERBILL

MEMBER
1980 PLYMOUTH HORIZON
4 CYL
2WD
AUTOMATIC
80,000 MILES

I have a 1980 Plymouth Horizon that was in storage in my garage for six years. When I drove the car again, I noticed that the brakes pulled. I raised the front end, applied the brakes and noticed that the left front brake did not work. I assumed that the caliper piston had stuck, after the car set for six years. I replaced the caliper and tried to bleed the brakes. I pumped the brakes several times, but I was unable to get any brake fluid to come out at the bleeder screw. I checked the right side, and it did bleed properly. Could there be something else wrong with the left front brake, since I am unable to get any brake fluid to come out at the bleeder screw?

2 Replies

1DODGE2

MEMBER
21 POSTS

Hello and wellcome to the 2 CarPros Forum, Your brake system comes equip with a Hydraulic Proportioning Valve. It is a safety device when the brake system loses brake fluid and divides the front brake from the rear brakes. On some vehicles it pairs the left front brakes to the right rear brake. When the system loses fluid or has air in the system the valve slides and allows the brake system to cut off the affected system. This allows the operator to safely stop the vehicle. For example, your brake system loses fluid at the left front wheel, as you apply the brakes the valve slides and closes any pressure to the front brakes, letting the vehicle rear brakes only. With diagonal proportioning valve, if you lose pressure, for example, on the left front wheel, the valve slides to isolate the affected wheel and at the same time cuts off the right rear wheel. This enables the right front and left rear brakes to do the stopping. Please write back and let me know if it was helpful information.

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Sunday, November 22nd, 2009 AT 9:59 AM

CARADIODOC

MECHANIC
33,871 POSTS

Did you get this fixed? If not yet, is the pedal low and mushy or high and hard?

If it's low and mushy, loosen a cap on the master cylinder and open the bleeder screw and let it gravity bleed for a while. You might have to irritate the brake pedal a little, but never push it more than half way to the floor. Doing so will run the two lip seals down through the lower halves of the bores where they don't normally go and will tear the seals on the corrosion and debris that builds up there. Chunks of crud could be blocking the port, but that would cause a high hard pedal.

A more likely cause of a high hard pedal, especially after it was sitting for a long time, is rust buildup inside the crimp of the metal bracket attached to the center of the rubber brake hose. It pinches off the hose. More commonly hard pressure on the pedal gets fluid to flow to the caliper but the square-cut seal in the caliper isn't strong enough to push the fluid back so the caliper sticks applied. This happened to one of my minivans and a student's Neon two weeks later. It's the only two cases I saw in over 25 years of working on cars, but I've read about it a few times since. My symptom was a high hard pedal; light pedal force caused the van to pull to the right because the left caliper wasn't applying as hard, then it would pull to the left when the pedal was released because the caliper wouldn't release.

Caradiodoc

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Saturday, December 12th, 2009 AT 7:21 AM