Help Brakes slowly engaging on their own. 1994 Ford Ranger Xlt 4.0 2wd

[Tyler Hunn]

I have a small problem. My trucks front brakes start slowly grabbing after about like a half hour to an hour of driving in the city. I had no dash lights on in my truck until about a month ago and it is the parking brake light and the abs light. (I'm not sure my truck even has abs). Right at this time my brakes failed on me and
I couldn't stop. I ended up changing the master cylinder and all the rotors and pads. I bled the master cylinder with the included instructions. I then bled both the front calipers. It seems to me it is a chain reaction. Something like the master cylinder starts pushing more than its supposed to when im not pressing on the pedal. then it starts to heat up the caliper and the rotor. This then also heats up the brake fluid and it expands. Right when it happened I pulled over. I noticed my rims had alol of heat coming from them and the pedal was very firm right up at the top. I jacked it up and was not able to spin freely either one of the front wheels. I waited an hour and it was fine. It starts doing this roughly a half hour of driving in the city. If I hop right on the freeway it does not do it. until I start stopping at stop signs, etc. I would also like to note that I had a good 3 weeks of driving with no problem when I first put the master cylinder in. Also the truck sat for a long time and it has no back brakes whatsoever. I dont know why but on the ice I can hold down the brakes and the back wheels are still spinning. I think i just need to put new shoes on it and oil everything up. I did drive the truck like this for two years without a problem. This just started happening when I had the master cylinder issues. My brake problem lights are still on next to the speedometer.. Please help me nobody knows whats wrong. could it be a bad master cylinder or maybe I installed it Wrong or I'm having an abs problem or I dunno. this is weird.

 

[KARMAN]

It sound like sticking calipers.
How old are they ?
You made need to rebuild them.

 

[Tyler Hunn]

I first thought that but both tires are locked up evenly. its the same on both calipers. I dont think they could both be going out evenly at the same time. Im sure its something with the master cylinder. but im not sure. lol

 

[robertc1024]

I had the same problem. It's apparently quite common on Rangers. The pistons in the calipers get frozen. Just go to Rockauto.com or somewhere and buy new calipers. They're cheap. While your in there, re-grease your front wheel bearings, the grease tends to turn to coke when the rotors get that hot. The only tricky part is getting the slide pins out. They have retaining tabs on them. I pinched mine in with a pair of long nosed vice-grips and knocked them out with a 3/8" socket extension.

 

[adsm08]

Well, I don't think you have a caliper issue. I think you have a seal issue. Sounds like the rear seal for the brake booster. The one that lets atmospheric pressure in to push on the back of the diaphragm.

Easy test, if you can find a cap that will fit, remove the booster hose from the manifold and plug the connection. Then go for a drive. If your problem goes away with the booster unplugged, then you need a new booster.

Last time I saw one like this it was on a brand new Focus with a mirror with temp gauges installed. The joker who installed it drilled through the fire wall to run the wires for the sensor outside. He also drilled through the back of the booster.

 

[robertc1024]

OOOh - first time I'd disagree with you ADSM, sounds like a classic caliper sticking issue to me. If you're right I'll bow and scrape.

 

[xr75er]

I had a 1980 cheby luv pickup that would do this. I would be driving and then the brakes would just load up. had to pull off for a while so they could cool down. then drive for awhile longer. changed out everything but the brake hose's befor I got it fixed . It was the brake line hose's swelling closed.

 

[bobbywalter]

yeah...with the initial heat...its a viscious cycle...whether hose or caliper


as the heat builds the fluid expands.

 

[Tyler Hunn]

Im almost positive both my calipers and my high temp hoses are fine. Ill tell you why. As soon as it was so hot that it was grabbing I took the front wheels off. while it was still hot. both tires had the same amount of pressure on each individual front wheel. I tried to remove the caliper. I took the slide pins out. It was still grabbing. I tried to compress with a c clamp thing. they wouldnt budge. But..... I let the pressure out through the valve and it went in with my finger. Same on both sides. the pressure is coming from up top before the fork in the line. because of equal pressure on each caliper. I highly doubt both calipers or both high pressure flex tubes would go out evenly at the same time. and....... If i go drive my truck now its perfect. no rubbing ... nothing....but after about a half hour of city driving it starts to slowly grab on its own then it starts to heat up and that in turn continues to expand the fluid.

So last night i bled my front brake lines again and sure enough it was quite a bit of air in the lines. so I must not have bled them right the first time or my truk was on an inline or something... I dunno. butt.... well I drove it with no problems last night but im not sure if i drove it long enough for it to happen.

The weird part is I ended up having no brakes one day. I ended up deciding it was the master cylinder. I replaced it and everything was fine for three weeks. Now Im all of a sudden having this problem. and I dont know if your right about the rear seal either. I still have full brake power. Except when It gets hot. And there is absolutely no brake fluid leaking anuywhere. Im thinking I might have a bad master cylinder. Im going to drive my truck around to today and take note on exactly what its doing. Because this is strange. Me and my dad seem to think its the valve ion the master that isnt letting the fluid recirculate. so The piston isnt sliding back far enough to release the small pressure so that keeps a slight amount of force on the brakes which then heats up yada yada.....................

Ill keep you all informed. oh and I even called the dealer and they said they are not even sure. but to check my calipers. I already did that they are fine.

 

[Tyler Hunn]

I had a 1980 cheby luv pickup that would do this. I would be driving and then the brakes would just load up. had to pull off for a while so they could cool down. then drive for awhile longer. changed out everything but the brake hose's befor I got it fixed . It was the brake line hose's swelling closed.

just for shits Im gonna go buy them right now and change them. I hopoe ur right. but why would they both do it all of a sudden now.
?????

 

[Snoranger]

I run into the same problem once in a while on forklifts. The brakes will start to "stick" after being used. Let it sit and they will be fine. It almost always turns out to be the master cyl adjustment. If the master is slightly over adjusted it will never let the pressure completely return from the lines. Every time you push the pedal it gets a little tighter, as it leaves a little more pressure each time. Try unbolting the master and adjusting the pushrod in the booster.

 

[Tyler Hunn]

I just drove about ten miles and right when i got around my house i could feel them starting to grab again. I do believe this is my problem. I will be adjusting this tonight. So how do I adjust it. do I turn it clockwise? counterclockwise? Unscrew something move it then retighten it? I dunno Ive never done that. I dont want to have to trial and error. since I have to bleed the lines every time i take off the master.

oh and I unplugged my vaccuum lines to check if it was the booster and when i did this i noticed tranny fluid in the lines. I dont think this is good. I have a leaky seal. but i just put a quart a week in. My driveway has a little character. lol

 

[dasfinc]

oh and I unplugged my vaccuum lines to check if it was the booster and when i did this i noticed tranny fluid in the lines. I dont think this is good. I have a leaky seal. but i just put a quart a week in. My driveway has a little character. lol

I can think of no circumstance under which transmission fluid would be IN your vacuum system....

 

[Earl43P]

A4LD auto trans shift modulator is fed vacuum.

 

[adsm08]

OOOh - first time I'd disagree with you ADSM, sounds like a classic caliper sticking issue to me. If you're right I'll bow and scrape.

The only reason I'm not suspecting the calipers is because it is both sides. I admit that this is a very common symptom of a caliper just starting to get stuck. It's not quite as common for it to be both sides.

oh and I unplugged my vaccuum lines to check if it was the booster and when i did this i noticed tranny fluid in the lines. I dont think this is good. I have a leaky seal. but i just put a quart a week in. My driveway has a little character. lol

Trans fluid in the booster could damage it.

A4LD auto trans shift modulator is fed vacuum.

And ^that^ is where it came from.