F600 ghost brakes
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Senior User
Joined: Oct 2003
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From: Joyce, WA
F600 ghost brakes
On my old girl I have a problem with my rear brakes. For the first 30 miles or so everything is good. Pedal feel is firm, truck stops good and straight, 3/4 to 1 inch of free pedal travel. After the 30th or so mile the pedal gets firmer free travel disappears and the right rear brake drags. It drags enough for the brakes on that side to smoke a little to alot. After the truck is parked for 10 to 20 minutes everything is fine for another half hour. Master cylinder is three years old. All wheel cylinders are less than that. It has the original type of hydra-vac booster system. I run 18 inches of vacumm at idle and very little at speed. (I have a heavy foot) I plan on backing off the right rear brakes tonight or tomorrow to help the problem, but I am not confident that is the best and final solution. Any suggestions?
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Joined: Aug 2004
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From: Los Angeles
Back the tension adjuster off and if you can check the shoe return springs and retaining pins. Bleed that wheel cylinder and check the color of the fluid. Try to pass enough fluid through the line to clean out whatever's there. If that only evens out the locking of the rear brakes, it's the residual valve.
Fleet Mechanic
Joined: Dec 2005
Posts: 1,603
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My truck is doing the same thing, an F6. There should be no residual check valve in
the master cylinder it is in the booster. I have found the booster to be sticking.
I know 48 to 52 boosters are hard to find , so I bought a later one from Napa, Just
make a new bracket a little different shape but they all do the same thing.....
the master cylinder it is in the booster. I have found the booster to be sticking.
I know 48 to 52 boosters are hard to find , so I bought a later one from Napa, Just
make a new bracket a little different shape but they all do the same thing.....
5th Wheeling
Joined: Dec 2005
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I had a '67 MGBGT that had the same problem, they were disk brakes in the front, but I suppose the same problem could happen to drums.
It took me forever to find the problem, it turned out to be the flexible brake lines were deteriorating on the inside, (outside looked fine) and strips of rubber were acting like a valve, not allowing return pressure through the brake line, locking up one brake in front.
Oh, back brakes are the prob, never mind... sorry...
It took me forever to find the problem, it turned out to be the flexible brake lines were deteriorating on the inside, (outside looked fine) and strips of rubber were acting like a valve, not allowing return pressure through the brake line, locking up one brake in front.
Oh, back brakes are the prob, never mind... sorry...
Last edited by bobadi; Feb 8, 2006 at 11:39 AM. Reason: mistake
Senior User
Joined: Aug 2004
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From: Los Angeles
Bobadi, that is a good possibility. Trucks have a rubber line in the back from the chassis to the axle and if the right brake is set tighter it would be the first to lock up if the rubber was valving inside the line.
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Senior User
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From: Joyce, WA
This is kinda scary I have been working on MG's for the past twenty years and have currently reduced down to one '71 BGT. All of my MG's have had the same problem with brake hoses front and rear and clutch. I never even considered that possibility. Thanks for the suggestion.
Logistics Pro
Joined: Feb 2005
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From: Upper Left Coast
Howdy,
The 54/55 service manual talks about this as "Brakes Lock During operation"
Possibly caused by a restricted by-pass port in the master cyl, improperly adjusted pedal linkage, swollen piston cups, or by dirt in the fluid.
Assuming that your wheel cyls are ok... I would replace the master cyl (or rebuild it...Kit is about $15) Then replace or rebuild (have it rebuilt) the booster. I was very lucky to find a rebuilt booster at Cascade Friction Materials in Tacoma, Wa for about $130. THey had it on the shelf for my 55 F-600. I know they are expensive. shop around. If it's screwed up you want to get another one. I don't think you can find rebuild kits for them anymore. Bleed the whole system following the service manual procedure.
Oh....post some pictures! THe more B I G trucks the better!
Good luck,
Rick
The 54/55 service manual talks about this as "Brakes Lock During operation"
Possibly caused by a restricted by-pass port in the master cyl, improperly adjusted pedal linkage, swollen piston cups, or by dirt in the fluid.
Assuming that your wheel cyls are ok... I would replace the master cyl (or rebuild it...Kit is about $15) Then replace or rebuild (have it rebuilt) the booster. I was very lucky to find a rebuilt booster at Cascade Friction Materials in Tacoma, Wa for about $130. THey had it on the shelf for my 55 F-600. I know they are expensive. shop around. If it's screwed up you want to get another one. I don't think you can find rebuild kits for them anymore. Bleed the whole system following the service manual procedure.
Oh....post some pictures! THe more B I G trucks the better!
Good luck,
Rick
Last edited by HT32BSX115; Feb 8, 2006 at 06:57 PM.
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From: Joyce, WA
OK guys. I'm sure the old girl is haunted now. Replaced the rear brake hose and that made no improvement. After doing that all I did was put fluid in and I had working rear brakes, I did not bleed them and they worked. They still slowly bound the drums so no improvement there. Yesterday I took the junction off the back of master cylinder and cleaned it out, ran new lines to and from hydro booster and one new four foot line towards the rear (stuck fitting). Put fluid in mastercylinder and pumped peddle. After a dozen pumps I had brakes. Again no bleeding anywhere! Brakes worked real good, stopped straight and rear brakes would lack up under real hard brakeing. Rear brakes then started to drag once more. Limp her home. I ordered a new booster this morning as I believe that is the problem. How can I have big air pockets in the brake system and then have them gone without bleeding? Maybe I'm on to something. The new booster will go on sometime this week. I'm thinking I will need to bleed the entire system after I put that on.
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Logistics Pro
Joined: Feb 2005
Posts: 3,952
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From: Upper Left Coast
There seems to be a lot of Big Ford trucks in the NW....
It might be fun to have a Big truck "meet" in the future!
By the way post a couple of pictures when possible. Everyone likes to look at big trucks!
Good luck on the brake job!
Regards,
Rick
It might be fun to have a Big truck "meet" in the future!
By the way post a couple of pictures when possible. Everyone likes to look at big trucks!
Good luck on the brake job!
Regards,
Rick
5th Wheeling
Joined: Dec 2005
Posts: 35
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Originally Posted by HT32BSX115
There seems to be a lot of Big Ford trucks in the NW....
It might be fun to have a Big truck "meet" in the future!
By the way post a couple of pictures when possible. Everyone likes to look at big trucks!
Good luck on the brake job!
Regards,
Rick
It might be fun to have a Big truck "meet" in the future!
By the way post a couple of pictures when possible. Everyone likes to look at big trucks!
Good luck on the brake job!
Regards,
Rick
Senior User
Joined: Aug 2004
Posts: 327
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From: Los Angeles
The beauty of the these trucks is that the brake systems are nearly vertical, so air pockets will rise back up to the master cylinder. I put all new wheel cylinders on my '60 F-100 and filled the master cylinder. Next morning she was ready go. Did you back the tension off the shoes on that side?
Hotshot
Joined: Oct 2004
Posts: 15,882
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From: Durham NC
Check for a leaking axle bearing seal, I have seen where axle lube leaking into the drum would cause the lining to get sticky when warm since the brakes are self energizing the dragging shoes would soon lock up the drum. When the drums cooled the shoe would retract until the next time it got heated up.
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Senior User
Joined: Oct 2003
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From: Joyce, WA
I will try to do pictures soon. The home computer is on the fritz so I'm doing this from work. There is another 56 f600 in Port Angeles. Truck looks good and is a work in progress. These things are everywhere. Axracer- interesting theory. Both sides are dragging now and it looks like the right rear is leaking axle lube. Discovered that this weekend while backing brakes off. I am going to chase this thing down. I'll update when I have more info.
Logistics Pro
Joined: Feb 2005
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From: Upper Left Coast
It's just worth it to replace the wheel bearing seals.
If the bearings are questionable....replace them too. NAPA can get all of this stuff. You'll be glad you did.
If the bearings are questionable....replace them too. NAPA can get all of this stuff. You'll be glad you did.
Originally Posted by 56f600
I will try to do pictures soon. The home computer is on the fritz so I'm doing this from work. There is another 56 f600 in Port Angeles. Truck looks good and is a work in progress. These things are everywhere. Axracer- interesting theory. Both sides are dragging now and it looks like the right rear is leaking axle lube. Discovered that this weekend while backing brakes off. I am going to chase this thing down. I'll update when I have more info.