ando427

I have a 1991 F150, 5.8L 4x4, and noticed my brakes rubbing and getting hot. I figured since the truck has 200,000 miles and the original calipers that they were the guilty component. Since it was well time to replace some of the other components I threw down and got new rotors, pads, rubber brake hoses and master cylinder as well. So I put it all together, and bled the brakes. Went around all the wheels twice and made sure there were no bubbles coming out. Brake pedal felt firm so I put the wheels back on and drove around the block. Brake pedal now seems spongier than before and when I got back from my drive that was maybe 5 minutes long at neighborhood speeds I popped the front tires off and the rotors were very hot and the wheels were not moving very easily so it appears that it's stuck rubbing again. Could it all just need more bleeding? Any help or advice would be greatly appreciated.

ando427

How critical is it to grease up the caliper guide pins? Does the caliper actually slide on these during operation? I'm wondering if maybe I didn't grease them up well enough.

fltdriver

They don't have to be super lubed, some grease is plenty. Double check to ensure that you have everything positioned properly. When you bleed the brakes, if you have two people, G1 in cab G2 at brake, G1-pedal to floor, g2-open then close bleeder valve, g1-pedal up, then to floor, g2-open then close bleeder valve.

I've seen people pump the pedal with the bleeder valve open and that can introduce air to the line, making brakes spongy.

If you're by yourself then you need a vacuum kit or find someone to help.

Always check pedal firmness and make sure the wheels won't turn when pedal is pushed while truck is stationary, I have also seen a guy doing the Fred Flintstone Stop because he messed something up in the MC and didn't double check before going for a test drive, probably one of the funniest things I've ever seen, too bad this was before youtube and cellphone cameras, I'd really like to see the look on his face when he realized he had no brakes.

ando427

Thanks, that was the method we were using to bleed the brakes. I did notice a small amount of fluid weeping out of the nipple on the front brakes when I would open them and thought that might be the source of some air. I'm definitely going to go back through and re bleed the brakes; this should get rid of the sponginess.

Could the brakes sticking be tied back to air in the system too? I felt as though I was pretty thorough while bleeding the brakes the first time so if there is air in the system it shouldn't be much, could it still cause this?

ando427

Does this truck have a proportioning valve? It doesn't look like it does as far as I can tell.

ando427

Do the guide pins have to be installed in a certain orientation? I noticed there were tabs on one side. Does it matter if those face the caliper side or the mounting side?

fltdriver

Yes, because air compresses so when pedal pressed pressure builds, cylinder will eventually extend after a couple of pushes, yet when retracting the air can just re-expand still creating enough pressure to hold the cylinder out.

No.

Sorry, mine use bolts instead of pins so I can't help on this one.

Crownman

You didn't say whether you bench bled the master cylinder or not. If you didn't then there's most likely still air in the system.

03Mach1

When you bleed the system. After you pumped the breaks and he the brake pedal, when you opened the bleeder valve did fluid shoot our of it like a garden hose or just dribble out?

If you bleed it right the fluid should shoot out not dribble. I usually slap a piece of aquarium pump air lime over the valve so I can contain the spray but it should shoot out not dribble out. Maybe you didn't bleed it enough.

ando427

I did bench bleed the master cylinder before installing it. I just went out and bled it again on the truck, as well as going around at all the wheels and the RABS and got out all the bubbles. Brake pedal feels much better now, still a little spongy relative to newer cars, but I'm thinking that's just how these pedals are.

After about a 10 minute drive around the block, I reached my finger inside the wheel opening to touch the brake rotor and it was quite hot; to the point where I would definitely not want to leave my finger there for more than a few seconds or it would begin to get very uncomfortable. I guess I'm wondering if this is ok. I know that brake pads should always be right on the rotor so you're not wasting pedal travel, and that friction will turn to heat, I'm just not sure if this is excessive.