79 F250. Dual piston calipers.

The brakes on my truck have been squealing ever since I bought the truck. Not when going down the road just when braking. So I thought I would change the brake pads. The pads I took off had a lot of life left in them but I thought I would change them anyway. I took the cap off my master cylinder and got out my big C clamp to push the pistons back in. Both sides would not go in any farther. So I thought "ok, that is as far as they will go" since like I said earlier, the old pads were almost as thick as the new ones. So I put my new pads on and getting everything back on the rotor was tight. They fit but both sides I had to tap them on with a hammer. Last night I am headed to an event about an hour away so I decided to drive my new prized truck!! I get about 10 miles from the house when I notice that burning brake smell. So I stop and I notice that the drivers side front is smoking, white smoke. It isn't bellowing smoke, and I only noticed it when I crawled under the truck but there was a little white puff of smoke coming off the rotors. So a friend that was on his way to the same place was coming up behind me. I parked my truck and rode with him. After the event he dropped me off at my truck and I drove it back home. When I drove it home I did not notice any smell at all. I am headed out to church in the truck now so we will see what it does.............My main question/concern is that I couldn't push the pistons back in with a c clamp. I would say that the pistons are sticking out about a quarter on an inch, like I said, the old pads weren't much skinnier than the new ones, I just changed them to see if it helped the squealing.

 

Stuck calipers?

 

I would have to agree when the OP hammered in the new pads and used the c-clamp one of the cylinders or both became bound in the bore is a more likely scenario .. To fix it you'll have to free the piston and this would be best done with the caliper off ..

 

I think you are both right. I think new calipers are the answer. There are two things that makes me thing the calipers were already seized up before I changed pads. Obviously the first is the fact that neither of them would go back in with the C clamp and the other is in my driveway I did some hard braking and the only set of tires I could get to lock up is the back. So I am thinking that my front brakes may not have been working ever since I bought the truck. But, the truck stops good so I am second guessing that theory since most of the braking is coming from the front. I would think that if I only had back brakes I wouldn't have much stopping power. I also don't think there is any reason that I should have had to tap the calipers back on with a hammer...................

 

Sounds like you are getting it figured out. My '78 with (original) twin piston calipers had a bad pull. One caliper was "frozen" and not operating. A set of Cardone reman calipers fixed that. I also changed the front flex hoses... they can collapse internally and hold pressure on the caliper causing a drag. Even with new calipers it was a snug fit with new pads. I did have to give a little push to get the calipers on. They also ran warm for a couple hundred miles until everything seated... no smoke but a bit warm.

In general, an empty PU has excessive rear brake bias so dragging a rear wheel in low traction situations is not always a sign of trouble... if you put 500# on the tail and it still does it and/or brakes feel weak when loaded that's strong indication of a problem with the fronts.

Last comment on bleeding... a little air in the front circuit will make it weak. These are tricky to bleed with the prop valve. I did not know the "pull the pin on the prop valve" trick and went through lots of fluid, ~2 qt, getting the job done.

 

I am going to take it out for a drive this afternoon and see if they heat up again. This morning as I went to church I went out of my way to get a few more miles on the pads and they did not heat up or smell. I made it about 12 miles or so last night when this all started. So I am going to take it out on the highway and see if they heat up again. Best situation is that I am just being worrying about it to much and it was just the pads burning off a little bit. Last night was the first time driven with the new pads. I could smell them and I saw just a hint of smoke when I crawled under the truck. Also, I didn't have to beat the brake caliper back on, just had to tap them on so maybe that is normal?

As for the hose, I had a buddy tell me the same thing. His wife almost burned their vehicle down with brakes sticking. He changed calipers and it didn't help. Come to find out the inside of the hose had collapsed.

 

After the last two posts with more info from the OP there could be more to it ..

Blue and whites point is a likely scenario
Also if the master cylinder was replaced and not bench bled and possibly the adjustable push rod that is at the back of the master cylinder may be out of adjustment ..

 

Also, is there a way to "check" the caliper? If I pull the brake pad that sits on the pistons and press the brake pedal can I check to see if it pushes the pistons? I don't want to do something stupid and push the pistons out!!

 

You can take a piece of wood that covers both pistons and using 2 c-clamps clamp it in place just so it begins to hold ..Then put some hydraulic pressure to it (not a lot but enough) .. Then let some off on the c-clamps if both pistons move outward then your good .. Relieve pressure at brake bleeder before taking off the c-clamps .. You should be able to tell if one piston is stuck and not the other also ..

 

10-4

I am hoping that I am just being a worry wart and it was just the new pads burning a little bit. Like I said before. I only changed pads because there was some squealing when stopping and the "old" pads looked pretty new and almost the same thickness as the new pads. So hopefully it was just those new pads burning off a little bit!!!

 

Alright, The drivers side was the side that had a little smoke coming off of it. So I started with that side. I put a 2x4 up there with my C clamp and gave it some brake pressure. I didn't have my 2x4 in there real snug and it pushed it out. Both pistons pushed out a little bit. I pushed them back in as far as they would go with my C clamp. So apparently they are functioning. Hopefully it was just me worrying too much and just was the new brake pads burning off a little because of the snug fit. I will put it all back together and take it out for a test run and see if they start getting hot again.

 

Well, after all that messing around I put the old pads back on! After pushing the piston out a little (note I said piston and not pistons as the bottom piston didn't come out any) I couldn't get the top one to go all the way back in. The new pads have a thickness of 9/16 and the old ones were just right around 7/8. The new pads wouldn't fit but the old ones did. Very snug, had to use the hammer again. Took it for a 12 mile trip average speed of 55 and got no heat, no smoke and good braking. So, I bought this truck to restore and here next week it is getting all new universal joints so while I am spending $$ on that and having the front all torn apart I think I am just going to put new calipers on. At the end of August it is getting a new motor. Might as well go through it and replace stuff like calipers that are probably original to the truck!!

 

I agree ..

 

Be a great time to inspect .... and replace if any question at all .... the rubber lines ..... all of them.

First few posts I was thinking the flex line from frame to axle if 4WD .... lines will do that sometimes, develop a flaw inside that closes and blocks the brake line so no relief.