84' F-150 brake/pull question

[FMF300EX]

Hey I'm asking about my 84' F150 w/ the 351w in it.

I've been having a problem for quite some time now that I have pretty much narrowed down to the brakes hanging up, but I have no clue why.

Every now and then the truck will start to pull hard to the right, I can't figure out any particular thing that would be causing the caliper or drum (not sure which one is hanging) since it will do it at times when I haven't just gotten off of the brake pedal or have touched it at all.

I did notice that when I had 36's on, it did not hang up and pull to the right at all- I'm guessing the added weight of the tires had something to do with it. (Note*- I had the 33's on prior the 36's. I had it aligned with the 33's and it still did its pull, slapped the 36's on and it stopped pulling, went back to 33's and the pulling continues)

I do know that I have to replace the master cylinder because it has a slow leak from where it mounts to the booster and will start to drain the back resevoir, but I do not think this is causing the problem since it was doing it before the master ever started leaking.

Tryed to explain the situation the best I could, sorry if it is uncomprehendable. Asked my shop teacher about it since it was previously his work truck, but he has not really given me much more information other then it must one of the brakes hanging up, so not much help there.

[J0R0]

It's probably the flex hoses going to your front calipers they can swell on the inside and hold pressure on the caliper.Replace them as a pair. You also need to try bleeding them real good alittle air can cause this also. Good luck

[autotech2]

[color=black][font=Verdana]Next time the truck pulls jack up the front end and see which wheel does not rotate freely. Then crack open the bleeder screw on the caliper of the wheel that's hanging up. If the wheel spins fine with fluid coming out of the bleeder and pressure relieved, then it's a collapsed hose acting like a one-way check valve. If the wheel is still locked, it's either the caliper piston or sliders hanging up. Like the other gentleman suggested, replace both hoses and calipers in pairs. We deal with all kinds of F-series problems.

[FNA]

I suggest that since you suspect the brakes, you inspect the brakes. Seems to me the natural thing to do.

[dfordski]

Many early to mid 80's trucks had a proportioning valve mounted on the side of the master cylinder that was prone to malfunction from fluid contamination, especially solid particulates. They tend to act up after major brake work &/or flushing. Especially if flushings had been few & far between. The symptom can also disappear if the particulates dislodge themselves. I think they were done away with by 86-87 because of being so problematic . Lacking that item, it"s usually a hanging caliper due to a restriction in those little bastard return hoses as others mentioned. This is also caused by chronic fluid contamination (moisture becoming asidic) & redundant thermal expansion/ contraction. Synthetic cuts out alot of this crap & by law must be compatible w/ all seal materials normally used for their specified application.