ABS LIGHT
#1
#2
RF Veteran
iTrader: (1)
If possible go to a gravel road and see if both front brakes are the issue or just one side.
Also for the rear
Or does it pull to one side?
Does the brake pedal come all the way up?
Can you lift it more with your foot, or hand?
There are a few things that can cause this.
Broken return spring
Broken/open atmosphere valve on power booster
Flex hose
stuck calipers
master cylinder problem
Power booster uses engine vacuum on one side of its diaphragm
The other side of diaphragm, facing the cab, there an atmosphere valve on the brake pedal rod.
When you press on brake pedal it opens the atmosphere valve allowing outside air pressure to assist you in pushing down on the pedal.
If brake pedal is not coming back up all the way then atmosphere valve stays open applying pressure to brakes.
Or if atmosphere valve is leaking then pressure is being applied
Also for the rear
Or does it pull to one side?
Does the brake pedal come all the way up?
Can you lift it more with your foot, or hand?
There are a few things that can cause this.
Broken return spring
Broken/open atmosphere valve on power booster
Flex hose
stuck calipers
master cylinder problem
Power booster uses engine vacuum on one side of its diaphragm
The other side of diaphragm, facing the cab, there an atmosphere valve on the brake pedal rod.
When you press on brake pedal it opens the atmosphere valve allowing outside air pressure to assist you in pushing down on the pedal.
If brake pedal is not coming back up all the way then atmosphere valve stays open applying pressure to brakes.
Or if atmosphere valve is leaking then pressure is being applied
Last edited by RonD; 05-18-2016 at 08:47 AM.
#5
RF Veteran
iTrader: (1)
If pedal comes back all the way the power booster is OK.
Power booster's push rod isn't attached to Master Cylinder, it just sits inside Master and pushes on Masters piston when you push on the pedal.
And power booster has it's own return spring, pushes brake pedal back up
It could be the Master is your problem if it's piston return spring can't push master back.
BUT(big but) it could also be a collapsed flexible brake hose is causing limited return flow to master so it can't return fully.
When you push down on the brake pedal the master pushes fluid out to all 4 slave cylinders(calipers), so flow is like this:
Brake pedal>>>>>>>master>>>>>>>>>flex hose>>>>>>brake slaves
Then when you release the pedal then masters spring pushes master piston back and pulls fluid back releasing pressure at the slaves:
Brake pedal
Power booster's push rod isn't attached to Master Cylinder, it just sits inside Master and pushes on Masters piston when you push on the pedal.
And power booster has it's own return spring, pushes brake pedal back up
It could be the Master is your problem if it's piston return spring can't push master back.
BUT(big but) it could also be a collapsed flexible brake hose is causing limited return flow to master so it can't return fully.
When you push down on the brake pedal the master pushes fluid out to all 4 slave cylinders(calipers), so flow is like this:
Brake pedal>>>>>>>master>>>>>>>>>flex hose>>>>>>brake slaves
Then when you release the pedal then masters spring pushes master piston back and pulls fluid back releasing pressure at the slaves:
Brake pedal
Last edited by RonD; 05-23-2016 at 10:30 AM.
Thread
Thread Starter
Forum
Replies
Last Post
RangerSkippyRoo
General Technical & Electrical
3
05-25-2009 10:25 AM