front brakes binding

[RustyBucket]

I haven't driven either one of my trucks much for the last 8-9 months. I had some health problems and then this Coronavirus mess came along. A week ago on Saturday morning I took my '71 GMC on a driving car show with about 50 other cars & trucks. I was lightly riding the brakes along behind another vehicle cruising through a neighborhood. The brake pedal got hard, right up at the top with no travel. I was having to use more throttle to keep the truck rolling because the front brakes were dragging. I got out of the way and let it stop and it felt like I had the line lock set... and I DON'T have line lock. The front brakes were hot as hell and smelled. After it cooled off for about 45 min. the pedal eased up and it drove home normally. I took it around the neighborhood Sunday afternoon and it did it again, I had to let it cool before I could come home. Factory power disc on the front/drum rear. It's been 4 or 5 years since new hoses, pads, rear shoes, fresh fluid. Nothing was leaking so I didn't change rear wheel cylinders or frt. calipers. Probably has 4 or 5 thousand mi. since then. Brakes were fine last time I drove it a month or so ago. Guess I'll start by looking at the front calipers & see if one/both are stuck.

[Bigdav160]

Or is the fluid not able to return to the master cylinder? Blocked compensating ports? misadjusted pushrod? The symptoms do sound like the hose problems we had in the '80's through the '90's.

[Sheepdip]

Originally Posted by Bigdav160

Or is the fluid not able to return to the master cylinder? Blocked compensating ports? misadjusted pushrod? The symptoms do sound like the hose problems we had in the '80's through the '90's.

^^^^^^^What he said^^^^^^^ I'd sort through all those issues first. Your fluid is getting hot and expanding if it can't return or vent to the master cylinder it puts the brakes on.

[68Gold/white]

I agree with the hose problem, can happen with any vehicle, any year...
GM used stainless steel caliper pistons, a wise thing. Rum dumb fords and dodges can have plastic pistons. The plastic pistons can cause the problems you have, BUT won't be the case with yours, having stainless pistons.

Buy some new front hoses. I'd get a new rear hose also, even if you don't install it now..

[RustyBucket]

Thanks for the suggestions... I replaced the hoses front & rear when I worked on the brakes. Trying to remember when that was. Time flies when your're old & retired, so it's probably been at least 5 yrs.. I guess they could've deteriorated, replacement parts often don't last like the originals. Until the truck sat for awhile the brakes had been fine so I'd be surprised if the push rod was the problem. I remember changing out calipers on a couple of my Dodge vans because of stuck nylon pistons in the calipers. I wonder if the bellcrank assy. behind the brake booster could dry up and cause a problem. Been delayed looking at it because of junk that accumulated on and around my shop & lift. While I was sick I neglected my trucks & shop & it's taking awhile to get going again.

[Boog]

The piston can get stuck in the caliper. I had that happen on my 71. And it was a daily driver. I rebuilt that one. Not much to it actually. Once I managed to get the piston out I polished up the bore and piston and put a new seal on it.