Having major brake issues ???
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Senior User
Joined: Aug 2006
Posts: 218
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Having major brake issues ???
Here we go...
What I have:
'59 F100, rear drum/front power disc conversion from '71 Lincoln including booster and master cylinder and block, late '70's Ford rotors & new mid '80's Chevy calipers. Newer brake lines.
Problem I have:
When truck is not running, pedal is somewhat stiff but doesn't build up pressure with more pumps. When running, the pedal goes all the way down and finally stiffens when about .5" away from floor, at the same time you hear a lot of air in the pedal movement. When truck is in gear, it barely stops from a roll.
What I have done:
Bled the brakes from pass. rear wheel, to rear driver, to front pass., to front driver. All flowing good and without air. No visible leaks anywhere.
What I'm thinking:
If the master cylinder was bad and leaking around the seal, I would notice fluid loss either in the cab or the outside firewall and there is none. On the other hand I'm not sure what I would encounter if the booster was bad.
Opinions welcome.
What I have:
'59 F100, rear drum/front power disc conversion from '71 Lincoln including booster and master cylinder and block, late '70's Ford rotors & new mid '80's Chevy calipers. Newer brake lines.
Problem I have:
When truck is not running, pedal is somewhat stiff but doesn't build up pressure with more pumps. When running, the pedal goes all the way down and finally stiffens when about .5" away from floor, at the same time you hear a lot of air in the pedal movement. When truck is in gear, it barely stops from a roll.
What I have done:
Bled the brakes from pass. rear wheel, to rear driver, to front pass., to front driver. All flowing good and without air. No visible leaks anywhere.
What I'm thinking:
If the master cylinder was bad and leaking around the seal, I would notice fluid loss either in the cab or the outside firewall and there is none. On the other hand I'm not sure what I would encounter if the booster was bad.
Opinions welcome.
Cargo Master
Joined: Feb 2008
Posts: 2,793
Likes: 128
From: Windermere Valley,B.C. Ca
Not sure about all the weird stuff, but the test to see if the booster is working is: with the engine off, push on the brake pedal and hold, start the engine and the brake petal should move down a little (couple of inches) and that is the booster applying its pressure. The low petal, no pump up, no brake, is puzzling, the “air” sound when applying is this vacuum going in / out of the booster or something in the brake lines? Almost sounds like not enough petal travel adjustment. Sorry.
Elder User
Joined: Mar 2008
Posts: 541
Likes: 0
From: Ardmore, TN / AL
I did see you said block so I assumed that meant the valve is installed. Sounds like air, I know you bled them in order but just sound like air. Trying bleeding with the truck running and safely blocked, I have seen that help get air out. Also your master cylinder could have leak by internally so you wouldn't have any leaks just not enough pressure to build up which usually means there is air still in there. One more question, has Dot 3 and Dot 5 fluid been mixed together in all these different components on the brake system? That can cause internal o-ring issues which is bad. Good Luck.
Lead Driver
Joined: Apr 2002
Posts: 8,813
Likes: 13
From: Littleton, New Hampshire
Did you bench bleed the MC? It sounds like air in the system to me. I had a heckova time getting all the air of of my brake system and I even used a Mighty-Vac on it. Also as Bob suggested, you need the rear brakes to be adjusted up pretty tight...
Senior User
Joined: Dec 2007
Posts: 335
Likes: 3
From: Centennial, CO
I had a truck once that the vacuum booster went bad on. If you are hearing air when pushing pedal, it could another possibility.
Just guessing.
Just guessing.
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Elder User
Joined: May 2006
Posts: 907
Likes: 1
From: Kansas City, Mo
Two items I've heard about. One the caliper needs the bleed holes at a certain angle. Since your installation is mixed parts this may be in the wrong position. The other item is the rod between the brake pedal and the M/C needs to be the correct diameter and correctly adjusted. Things to consider. chuck
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