Brake problems
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Cargo Master
Joined: Dec 2007
Posts: 2,037
Likes: 310
Brake problems
On my 2000 F350 I rebuilt the front end and was having issues with a sticky caliper...truck would go hard left when brakes applied. It would not right itself unless you pressed the pedal hard such that the anti brake situation was activated...pedal bled down. After several months of this it did seem to get better until yesterday. I had a trailer in tow and when pressing the pedal firmly I went over a bump which caused the pedal to pulsate a little. After this now when I brake coming to a stop it does fine if I apply steady even pressure, but if I increase pressure on the pedal it steadily goes to the floor. I checked the brake fluid and all seems fine. There are no dash lights on...Brake, Anti-Lock, etc. Could this be a leaking seal on the master cylinder...or maybe a leaking seal on the other caliper?
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Cargo Master
Joined: Dec 2007
Posts: 2,037
Likes: 310
Okay, so I replaced both the master cylinder and the hydroboost as it had a small drip on the inside of the firewall. Now I cannot get the brakes to pump up any pressure. I can turn the steering wheel from lock to lock fairly easily. However, now when I turn the steering wheel the brake pedal slowly sinks towards the floor.
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Cargo Master
Joined: Dec 2007
Posts: 2,037
Likes: 310
I put the plastic plugs in where the 2 lines...front and back...hook up, then filled the reservoir and cycled the piston cylinder several times.
Fleet Mechanic
Joined: Oct 2017
Posts: 1,704
Likes: 164
From: Southwest Ohio
When you bench bleed you use caps with nipples and attach small air hose that loops back into the top of the master cylinder. That’s how I’ve always bench bled.
Did you properly bleed the entire brake system, starting with the caliper farthest from the master cylinder and working your way closer?
When you start the truck and push on by brake pedal is it dropping to the floor or not moving at all?
— Dave
Did you properly bleed the entire brake system, starting with the caliper farthest from the master cylinder and working your way closer?
When you start the truck and push on by brake pedal is it dropping to the floor or not moving at all?
— Dave
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Laughing Gas
Joined: Jan 2005
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You need to properly bench bleed the master first and then the entire system. Also if you let air get into the ABS module you will need a high end scan tool that is capable of a "service bleed" to get air out of the ABS, something like the Ford IDS or Forscan.
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Thread Starter
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Cargo Master
Joined: Dec 2007
Posts: 2,037
Likes: 310
When you bench bleed you use caps with nipples and attach small air hose that loops back into the top of the master cylinder. That’s how I’ve always bench bled.
Did you properly bleed the entire brake system, starting with the caliper farthest from the master cylinder and working your way closer?
When you start the truck and push on by brake pedal is it dropping to the floor or not moving at all?
— Dave
Did you properly bleed the entire brake system, starting with the caliper farthest from the master cylinder and working your way closer?
When you start the truck and push on by brake pedal is it dropping to the floor or not moving at all?
— Dave
I have tried to bleed the entire system starting with the back passenger, then the back driver, the front passenger, and finally the driver front. I have done this about a half dozen times and there is still no firmness in the brake pedal and the pressure at the bleeder valves is non existent...it is just a steady drip rather than spurting out.
The pedal goes to the floor easily with the engine not running. With the engine running, you can push the pedal to the floor and it will push back up a little telling me the hydroboost is working. The pedal will not build up when you pump it with the engine either on or off.
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Cargo Master
Joined: Dec 2007
Posts: 2,037
Likes: 310
I did rent a vacuum power bleeder this evening and bled again at each of the four corners with no success. I am thinking tomorrow I need to power bleed the master cylinder and see what happens.
Fleet Mechanic
Joined: Oct 2017
Posts: 1,704
Likes: 164
From: Southwest Ohio
Keep bleeding the system and you’ll get the air out. It’ll probably take a while, so make sure you have plenty of brake fluid.
You are going to struggle getting the air out of the ABS module. What you can do, after you get all the air out of the brake lines, is drive your truck on wet grass and slam on the brakes, causing the ABS to kick in. You will again get pedal drop but then you can re-bleed the system. This is the long method of ABS bleeding, if you don’t have the specific tool.
Pedal drop means you are compressing air. Just keep bleeding and you’ll be successful.
— Dave
You are going to struggle getting the air out of the ABS module. What you can do, after you get all the air out of the brake lines, is drive your truck on wet grass and slam on the brakes, causing the ABS to kick in. You will again get pedal drop but then you can re-bleed the system. This is the long method of ABS bleeding, if you don’t have the specific tool.
Pedal drop means you are compressing air. Just keep bleeding and you’ll be successful.
— Dave
Fleet Mechanic
Joined: Oct 2017
Posts: 1,704
Likes: 164
From: Southwest Ohio
If pedal is going to the floor, you still have air. Clean fluid doesn’t mean all the air is out, as bubbles can be inside the line. Also, keep in mind a leak and draw air in to the system.
— Dave
— Dave
Thread Starter
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Cargo Master
Joined: Dec 2007
Posts: 2,037
Likes: 310
Pulled the master cylinder and see the problem. There is no rod on the end of the hydroboost so they are not engaging. Anyone know if that rod can easily be installed instead of pulling and exchanging the hydroboost?
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Cargo Master
Joined: Dec 2007
Posts: 2,037
Likes: 310
Luckily the parts store still had my core and I was able to pull the rod, spring, and star bushing then put it in the new hydroboost on the truck. I now have a brake pedal and good steering but am back to square 1 in that I still have a sinking pedal. There are no leaks that I can see and all four corners had good flow at the bleeder valves which to me rules out a blocked hose. I have read about the ABS unit and wondering if something in there is bypassing the fluid and what to do to correct it?