Almost left me walkin...
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Junior User
Joined: Oct 2004
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Almost left me walkin...
Just picked up a 50 F-1 a couple weeks ago, got it runnin, took it to town to put gas in it, left the gas station then the brakes slowly started to apply themselves. So i drove it till i could find a place to pull over. The master cylinder was full, i waited till the brakes cooled down and backed the brakes off so i could get home. Just before i got home it did the same thing again. So rebuilt the wheel cylinders and bleed all the old fluild out. The brakes worked good for a couple hours then it started doin the same thing again. Anyone else have the same problem? The only thing i can think of is it might be the master cylinder? Any help would be appriciated.
Trav
Trav
I'll have the Roast Duck
Joined: Jul 2002
Posts: 9,622
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From: Northshore, MN
do a bench-test on the master cylinder and see what it does. Does it do it after you've applied the brakes once?, thus setting the master cylinder rod into motion? Doing a bench test will show if the plunger is sticking or not.
Posting Guru
Joined: Dec 2004
Posts: 1,474
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From: Shasta Lake, Ca.
pedal all the way up.. Humm, U might have water in the system.. in some rare cases if there to much water it can Boil and apply the slaves while the master stays open.. And with the way the single sysems are, If the vent cap is clogged it will lock the brakes up.. I know that just about everyone here will tell U there no way it can happen.. but when water boils it want to expand and if the vent clogged,, the only thing it can push on is the slaves.. try just flushing out the system with new fuild and see if it helps any..
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From: Winchester
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Cargo Master
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From: Friendswood, Texas
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Postmaster
Joined: Mar 2000
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From: Waynesville, OH
I vote with redlightening. If the the MC push rod is not loose with the pedal released, you'll gradually build up pressure every time you apply the brakes due to the residual pressure valves. There is nowhere for the return flow to go since the MC is engaged all the time. That would also explain why the pedal is totally stiff when the brakes are locked up.
Lead Driver
Joined: Apr 2002
Posts: 8,813
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From: Littleton, New Hampshire
Had the same thing happen to me years ago on a car I put together with mismatched brake components. The problem was that the master cylinder push rod was too long. When the brake pedal was retracted the rod didn't come back far enough to allow the fluid back into the MC so everytime I hit the brakes more fluid was forced into the front calipers until the car would not move. The first few times it happened I had to open the bleeder valves to release the pressure before I could get the car back home. After I shortened the MC rod it was okay. 
Vern
Vern
Cargo Master
Joined: Nov 2004
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From: Friendswood, Texas
I'm just wondering how long the truck sat idle before he bought it and got it running. Also when was the last time these brakes received any attention? Anytime I resurrect something this old, first thing that gets done is ALL of the brake hydraulics gets replaced. My father told me he didn't care if whatever car I brought home would go, he just wanted to make sure it would stop. This was one of the few things that actually took when father told it to me the first time.
Replace the MC, and all of the wheel cylinders at the very least. Why take a chance. At least that's how I see it anyway.
Replace the MC, and all of the wheel cylinders at the very least. Why take a chance. At least that's how I see it anyway.
Senior User
Joined: Aug 2004
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Originally Posted by texan2004
Replace the MC, and all of the wheel cylinders at the very least. Why take a chance. At least that's how I see it anyway.
Does your system have a booster? If it does I'll bet the guys may be correct on a mismatched rod since it would have to be an add on component.
Roast em' if you got 'em
Joined: Mar 2005
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From: Rio Rancho, NM
If the truck had been sitting for quite some time then it might take more than one flushing to clean it up. I had a motorcycle do the same thing to me, the rear caliper would eventually lock the brakes to where I couldn't move. It took numerous flushings over several months to finally fix the problem. I even pulled the whole system apart (MC and caliper) to clean them up
I would check the pushrod, if that is not toolong then you just might have to do a serious cleaning of the whole system.
Good luck with it and welcome to the board
Bobby
I would check the pushrod, if that is not toolong then you just might have to do a serious cleaning of the whole system.
Good luck with it and welcome to the board
Bobby
Cargo Master
Joined: Nov 2004
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From: Friendswood, Texas
I would also replace the brake lines but some might say I tend to go overbaord with these things. Maybe, but the piece of mind is well worth it in my opinion. Again, at the very least, replace the MC and wheel cylinders.
Roast em' if you got 'em
Joined: Mar 2005
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From: Rio Rancho, NM
Carl,
Good idea, I forgot to mention that. The original brake lines on my 49 were almost completely plugged.
I ran all new lines on my 49 when I installed the 9" rear and the front discs.
Bobby
Good idea, I forgot to mention that. The original brake lines on my 49 were almost completely plugged.
I ran all new lines on my 49 when I installed the 9" rear and the front discs.
Bobby