Brake light on!!!

[pjm8047]

So I was test driving my RR today to check for any leaks coming for the valve covers that i replaced and when i passed the brake I heard a pop and brake pedal went to the floor and brake light came on. So I pulled over and check for leaks I didnt see any. I pumped the pedal and got hard again. I started driving again and after a couple stops pedal went back to the floor again.I have manual brakes.I replaced the master cylinder 3 years ago and its still under warranty .Im thinking thats the problem again because the same thing happend when I first replaced it three years.What do u guys think?

 

[Yatzee]

One would tend to lean towards the master being defective but there are other possibilities. The proportioning valve could be defective (binding) and there is a lot of air in the rear braking system from an improper bleed. The pop may be the valve releasing from a stuck position and the air in the line compressing causing the pedal to drop. I don't know your braking system weather it's disk/drum or drum/drum but wheel brake cylinders do tend to bind in position as do the caliper pistons. A quick release in this instance will send the pedal spiraling to the floor. Even rubber flex lines that have a rupture in the inner tube can cause strange events. It's probably time for a close inspection of all braking components before spending money on a hunch. I certainly wouldn't operate the car under these conditions.

 

[pjm8047]

One would tend to lean towards the master being defective but there are other possibilities. The proportioning valve could be defective (binding) and there is a lot of air in the rear braking system from an improper bleed. The pop may be the valve releasing from a stuck position and the air in the line compressing causing the pedal to drop. I don't know your braking system weather it's disk/drum or drum/drum but wheel brake cylinders do tend to bind in position as do the caliper pistons. A quick release in this instance will send the pedal spiraling to the floor. Even rubber flex lines that have a rupture in the inner tube can cause strange events. It's probably time for a close inspection of all braking components before spending money on a hunch. I certainly wouldn't operate the car under these conditions.

Its four wheel drum.I've always had brake problems with the car.First I had a hard pedal and slowly got softer and softer until it finally gave in today and I also having problems with fluid leaking from the cap of the mc.I tightened the bale so much I can get it off without a screwdriver and its still leaking till this day.

 

[badlite]

With 4 wheel drum brakes you should not have a proportioning valve, so your problem has to be the master cylinder.

 

[pjm8047]

With 4 wheel drum brakes you should not have a proportioning valve, so your problem has to be the master cylinder.

That what i figured. Its under warranty and a new one has been ordered. Its always something urgh.whats the best way to bench bleed it?

 

[440roadrunner]

One would tend to lean towards the master being defective but there are other possibilities. The proportioning valve could be defective (binding) and there is a lot of air in the rear braking system from an improper bleed. The pop may be the valve releasing from a stuck position and the air in the line compressing causing the pedal to drop. I don't know your braking system weather it's disk/drum or drum/drum but wheel brake cylinders do tend to bind in position as do the caliper pistons. A quick release in this instance will send the pedal spiraling to the floor. Even rubber flex lines that have a rupture in the inner tube can cause strange events. It's probably time for a close inspection of all braking components before spending money on a hunch. I certainly wouldn't operate the car under these conditions.

Sorry this ain't happenin. Air in the rear simply would result in no pedal ever

 

[Yatzee]

Obviously you don't understand why master cylinders are split into front and rear sections. If the rear line bursts you still have braking on the front providing it's not a "jam jar" master. How do I know? I burst my rear flex hose. My brake pedal lowered but came back up somewhat. Not sure what year of car he has so I have no idea weather his master is divided or not. Sorry, you have been given misinformation.

 

[pjm8047]

Obviously you don't understand why master cylinders are split into front and rear sections. If the rear line bursts you still have braking on the front providing it's not a "jam jar" master. How do I know? I burst my rear flex hose. My brake pedal lowered but came back up somewhat. Not sure what year of car he has so I have no idea weather his master is divided or not. Sorry, you have been given misinformation.

1971 divided.the car stops some what but pedal does go to the floor

 

[A383Wing]

if the brake light came on, it has a proportioning valve....that's what activates the light...you have lost pressure in either the front or rear hydraulic system....check your master cylinder and you might find it has a low level in one of the reservoirs....fluid is going somewhere.... you just need to find it...if no fluid loss....then master cylinder would be first suspect to replace

 

[pjm8047]

After i install the new mc im gonna bleed all 4 wheel clyinders too make sure all the airs out

- - - Updated - - -

if the brake light came on, it has a proportioning valve....that's what activates the light...you have lost pressure in either the front or rear hydraulic system....check your master cylinder and you might find it has a low level in one of the reservoirs....fluid is going somewhere.... you just need to find it...if no fluid loss....then master cylinder would be first suspect to replace

i once noticed that the front reservoir was emtpy aka bone dry.I topped it off i thought i was lossing from the cap. I wonder if i got tons of air in the system.

 

[idrivemopar]

Check your wheel slave cylinders if its drums all around, especially if your MC was dry, could be leaking out inside the drum, and you may not see anything on the ground, as its all spun up inside your wheel well and all over the inside of the wheel and drum!

 

[pjm8047]

Check your wheel slave cylinders if its drums all around, especially if your MC was dry, could be leaking out inside the drum, and you may not see anything on the ground, as its all spun up inside your wheel well and all over the inside of the wheel and drum!

It went dry about 4 months ago and it never went low again.

- - - Updated - - -

Ill check all the wc after i install the new mc. If the pedal goes hard after i install the new mc problem solved?

 

[pjm8047]

It went dry about 4 months ago and it never went low again.

- - - Updated - - -

Ill check all the wc after i install the new mc. If the pedal goes hard after i install the new mc problem solved?

Problem fixed.turned out to be a broken brake adjuster and star adjuster fell out of place