I have a '00 F-150XLT 4x4, 4-wheel disc brakes. when crawling to a stop, my pedal gets hard, if I let off and re-apply, the brakes are right there. Sometimes going down a steep hill the same thing happens. The ABS light never comes on. Contacts look all tight and are clean. I figured if it's ABS related, the light would definitely come on. Speed sensor? Hoping for some insight, as local dealers here are very expensive, especially if I can do the fix myself. Is it a possible master cylinder or power brake booster problem? Air in the system? Thanks in advance for any insight.

 

Tighter is better. If you have air in the lines, your pedal would be mushy. But you say they're to tight? This is just a guess, but that to me sounds like a stuck caliper piston not fully retracting when you let off the brake pedal.

Take your calipers and pads off and spray the heck out of the caliper pistons and all the contact points on the pads and calipers where they slide back and forth. (ie. the caliper slides).

If that doesn't help, you problably need new caliper(s).

 

When say "coasting" out of my yard, and hit the pedal, its hard, and there is no brake impulse, let off the pedal and reapply, and theres lots of brakes. Coming down steep hills to a complete stop it will do it too. I know this sounds like a weird situation, and in reality it is. I did the pedal test for the booster, and checked the check valve for the booster, they are fine, at least to my knowledge. It seems only at lower speeds it happens, I even pulled the hose off while the truck is running, and there seems to be lots of vacuum. When I say the pedal gets hard, its like the pedal fetches up, and no braking takes place, let off, and reapply and I have brakes. I don't want to go to my local dealer, because in the past, they seem to throw lots of parts on before they find the problem. My rotors all seem to be wearing evenly, and the truck doesn't pull side to side, so I would think it wouldn't be the caliper. I'm just a very basic do-it-yourselfer, but can do mechanical stuff with guidance. I appreciate the insight. Maybe I'll try bleeding the system, it couldn't hurt

 

check ur booster vac line it might be cracked! also take apart all the brakes and clean them make sure the slider is spotless or go buy a new slider (their cheap) well your in there check your rotors for damage since you have to wait for the parts to dry anyways! i would also bleed the brakes since it is a half an hour or less job with 2 ppl working together. if that aint the problem i would have the brakes looked at by a professional if your not comfortable. me personally dont tear in to brakes too much so i would rather have a friend or shop look deeper for me.

 

Definatley check your booster vac line. Also it kinda sounds like you've got glazed pads and rotors. But the booster vac line leaking sounds more like the culprit since it happens at low speeds when the vacuum pressure is the highest.

 

Gentlemen, thanks for the replies, Peacemaker, that really makes sense, as that is when it happens probally 95% of the time. I really appreciate the insight, you've all been very helpful. I'm going to check everything I can this week

 

Don't thank me, thank racerf150 man. He told you first.

 

Thanks to you all! Hopefully I'll get it figured out this week

 

Did you find out what it was?

 

I needed a rear line replaced, so I got it to my mechanic, as I didn't have the time to do it myself, I asked that he would take it for a drive to he what he thought, and when my wife picked up the truck yesterday, he said he thought it may possibly be ABS related, and he said it seems like its acting before it should, and only at low speeds. He said he turned it up on a straightaway and slammed on the brakes, and it was perfect, just at that crawling speed does it do it mostly, or on a hill. Sadly he doesn't have a diagnostic machine, so I assume I'm dealer bound. Is it possible it could be the speed sensor in the rear-end? He looked everything over, calipers, rotors, and everything were in order, and didn't see any brakes in the vacuum line. I pulled the check valve off myself, and it seems to be good. And again, there is no ABS light coming on Is a code reader a wothwhile investment, the ones that automotive stores sell? I may look into purchasing one.

 

That sucks. You've got me stumped too man. The only other thing I can think of is the master cylinder, or brake booster itself is bad. But it sure does sound like your losing vacuum pressure at low rpms somwhere in your braking system, thus causing the problem at slow speeds. If that's what it takes, I guess take it to the dealer.

 

The OBDII readers are for engine/emmision related issues. Seperate readers are used for ABS and are rather expensive from what i understand.

If you need a new brake line chances are there is air in the system. If air got in the abs system you need the scan tool to bleed the brakes properly (it cycles the abs on and off while bleeding).

I'd bet on a booster problem (I'm no pro). Vacuum is only half of how a booster operates. The other half is atmospheric pressure entering when the pedal is applied.

Great brake related articles.

Good luck and let us know what you find.

 

Seems Like Im having the same problem. Did you ever find out what the problem was?