brake advise needed

[biggs357]

I have a 1991 Bonnieville and was in an accident this am,my son and i are ok but as we were pulling away,my brake light came on and had almost no braking power.I was able to pull over and check the master cylinder and it was full and i didn't see any leaks around the tires.I drove behind my wife all the way home doing 15 miles per hour.

It will stop but the peddle goes to the floor and it takes about 30 feet to stop.I have checked the pads on the front they look fair.I have drum brakes on the back(i'm clueless)as to what i'm looking at.Other than having it towed to a shop and them charging me 680 dollars plus the towing fee.Is there any advice ya'll can give for finding the problem.

 

[Black69]

Sounds like you might need a new master cylinder. It's an easy fix and not to expensive.

 

[Spotteddog]

Master cylinder and/or proportioning valve most likely. During wrecks, brake pedals get stood upon far harder than you'd think in the adrenalin dump. The increased pedal travel, while exhibiting reduced braking action are the give away. It usually indicates that only 1/2 of the system is operating. Does the brake system low hydraulic pressure warning light in the dash, only come on when the pedal is pressed, or is it on constantly?

 

[cshoff]

Try bleading the brakes before you do anything else. I've seen instances where the brakes were stood on so hard that the inertia caused the fluid in the master cylinder to go forward and allow a little air to enter the lines. When that happens, you get the pedal to the floor symptom. If bleading the lines doesn't help, I'd bet the master cylinder is shot.

 

[USAF385]

+1 on the master cylinder theory.

Even if the rear drums were bad, you wouldn't have that much trouble stopping. The rear brakes do so little of the stopping.

 

[pred]

There may also be a balancing valve in there which if the balancing piston goes all the way to one side (F or R) The light can come on, Had this issue with a 95 Caprice, All power will go one way with very little fluid loss out of the side with leaky line.
Peter

 

[biggs357]

Spotted/the brake light has been on since i pressed the pedel at the light where i had the accident.I just came in from checking to see if any fluid had leaked out,but it's raining to hard to tell but the master cylinder still looks full.

Cshoff/i'll try bleeding them when the rain stops.It's been raining here about every day this week.

Also would anyone have a left side head light kit they would sell.

Hey guys thanks for helping,too.Keep the advice coming.

 

[Eagle 477]

Check your rear braks wheel cylinders... sometimes standing on the brakes real hard can blow the seals out....Look at the backing plate to see if there wet.... they leak down and you lose pressure...

Bob

 

[DeathGrip]

+1 on the wheel cylinders,cheack them out.If they cheack ok it is likley the master,sometimes they get internal leaks.Also is it ABS? some times dirt can mess those up to. Most likley the master cyl. in my exp.

 

[biggs357]

I still haven't been able to get under the car but i have taken some pics to help.

 

[Spotteddog]

Biggs,
Follow the two lines coming out of the master cylinder downward towards the frame rail to find the proportioning valve I wrote of earlier. It will be a metal rectangle with two lines going in and 4 to 6 lines coming out of it and a switch built into it (low hydraulic pressure switch). The proportioning valve is a device that has two functions. First, to properly distribute hydraulic pressure to the front disc brakes (65%-70%) and rear drums (30%-35%). Second, it allows a "split hydraulic system" to exist. So that the loss of one line or device anywhere in the system, doesn't cause a catastrophic loss of brake fluid. Often when the brakes have been hammered hard (accident) the proportioning valve spool will have been actuated past it's normal range of motion and the piston will become lodged on rust or dirt in the interior of the valve. Once the piston moves and sticks, it cuts off some hydraulic circuits. Look on the valve's exterior for a rubber boot type dirt shield, under which you may find a plunger which can be reset. Some need a probe to be inserted in order to re-position the piston. Not all proportioning valves have the reset feature however?
If it'll take the "reset" of the piston it may help return some braking long enough to get it to a shop?
GOOD LUCK!
BE CAREFUL!