Topic: Sticking Brakes-'81 4X4

[Speed]

Hi all;
   When I got this truck the brakes were all flogged,so I started with the most critical first. I replaced the front pads and calipers. The old ones were relatively clean-n-dry,but the calipers were 3/4 froze up and the pads were just getting into the metal. Everything worked fine from then on,less than 2,000 miles,until recently;the brakes started dragging,first at the rear. I waited until they cooled,pulled the drums off and cleaned everything up as well as I could,backed the adjusters off about a full turn,and that seemed to get me going again. (I knew the rear needed new brakes as well as axle seals,but the budget couldn't cover that.) THEN,I started having the same issue with the FRONT brakes;Cold,they were fine,within a couple of miles,they got tighter,the pedal got higher,and eventually it required four wheel drive,low range,low gear to keep the front tires from skidding me off the dirt road going up to the Landfill to haul trash (Sunday). I discovered that pushing the brake pedal with all my strength and holding it for about 15 seconds got the brakes to free up enough to finish the dump run and get home. Anyone have an idea what happened? Has anyone else had this happen? Next relatively warm day I get,I plan to pull the front wheels and see how everything looks. I'm wondering about the master cylinder. That's the only place the front and rear brakes connect,and it just feels like too much of a coincidence for BOTH ends to screw up so close to the same time. If the problem is different,Front/Rear,I've noticed the steering knuckles are leaking pretty bad lately,but I can't see how the gear oil could run off them and go clear over into the brake pads. I guess anything's possible.
   Thanks for your help.
   Speed

[emsvitil]

Sounds like there's not enough freeplay at the brake pedal.

When there's not enough freeplay,  the brake fluid can't get back into the reservoir.   Fluid warms up, expands,  starts applying brakes.    Which warms up the fluid even more.

[Speed [OP]]

   That occurred to me too,but why would it happen with 2,000 miles on the truck since the new front brakes? I never did anything with the M/C,and it worked fine for a good while after.
   I ran into that very problem on my GMC when I changed it over to a split reservoir master cylinder and adjustable proportioning valve,but I was expecting it then-I was building a new system with unrelated parts.
   MY mind keeps going back to either oil contamination on the front brake pads or plugged ports in the Master Cylinder.  I guess it's possible the calipers have gone wonky,but BOTH at once? Not too likely. Maybe a pinched brake line? i don't think I've had it anyplace that rough.....
   Well,the BroncWorth is running relatively well now,so I'm not without transportation,so I can wait for a warmer day to investigate the brake problems. Until then though,any ideas you might have will be welcomed. 
    Thanks again!
   Speed

[OOPS]

Things I would check:

Enough free play in the pedal and it is not sticking down after applying brakes. I would this first.

MC return holes not gummed up, take MC apart. Happened on my Triumph MC.

[Speed [OP]]

When the truck hasn't been driven for a day or so,I have about 1/3 of the pedal's travel free,then a good firm pedal;it gets a little less freeplay each time I use the brakes,and after the second or third use the brakes seem to start to drag worse and worse.
   Something else that occurred to me-if the master cylinder got moisture in it,could some water contamination make the brakes do this,or would water heat up and make steam,making the pedal drop instead? Or maybe gear oil contamination is gumming things up to a point that nothing's returning.
   I'm getting a longer and longer list of "needs" on this truck. On the "Plus" side,since I got into it as a trade,I'm not out much $,so I can probably swap the motor,do ALL the brakes,gaskets and seals on both axles,replace the smashed left door,weld up the cab,give it a new windshield,etc. and be happy with the results. It'd STILL be a rolled,rusted,banged up Toyota truck,but it'd be solid,reliable and road capable,and the "patina" (to put it very mildly) would be a DEFINITE attention-getter. The work it needs would be a couple of years of work,but now I have reliable transportation again,so I'm okay with it.
   Speed

[dt]

Ive never had this happen ,but I would check the emergency brake, cables etc. Also the inline valve in the vacuum line that goes from the intake to the booster,its behind the heater hose on the firewall. On the Triumph,they use British brakefluid and I bet  someone mixed different kinds of brakefluid.Ill be curious to hear the answer on this one! Remember you adjust the front brakes by adjusting the rear brakes.

[Speed [OP]]

 The E-brake cables and related parts are long gone/disconnected/bypassed;they often do this on ranch trucks out here so as to avoid getting them whanged flat on rocks,strung out behind the truck by a broken off fence post or,at best,freezing up in the Winter,out in the middle of God's Country,preventing the truck from getting home until Spring. The ones with winches sometimes get those hydraulic E-brake set ups.(Mico-Lock??)
   I really believe a new Master Cylinder and a brake fluid flush would solve this particular problem,but it's STILL going to need all the axle seals and gaskets and complete rear brakes to make it all work right. I probably won't be using this truck as an actual work truck,but plans change frequently depending on the project I need to complete and what capabilities I need. I'm thinking it'll be good for travel (Good gas mileage) when I need to haul more than I can fit into the BroncWorth.
   Speed