2004 NBS f150 stx 4x4 w/ 133k

i was coming to a stop sign at low speeds(first stop) and the truck would not stop. the pedal felt like it was jammed, i was literally standing on it full force. What could cause this?

the same thing happened to my fiancee and i didn't believe her. fortunately no traffic was coming. this is an accident waiting to happen

recently i changed the passenger caliper, i only bled that caliper. thinking i should bleed all 4 starting with the right rear. sometimes at the first stop the pedal would get what i would call spongy crunchy feel for a second. it usually only happens at the first full stop, and only sometimes. this other thing seems related. is this what air in the brake lines does.

it has only happened twice, other then that it drives fine.

 

Air in the lines causes a spongy pedal, not a solid locked pedal. You could be having an issue with the booster or the ABS, possibly the master cylinder.

You may want to get a pro to look at it, brakes are too safety critical to screw around with.

 

I agree with glc, a "soft" or "spongy" pedal would be air in the system. Your description doesn't sound like that at all. Brakes are far too critical to just take a guess at. If there's a problem with the ABS a parts store scanner won't find it. If it were me I'd take it to a pro, money well spent IMHO

 

thanks guys

i forgot to mention my ABS light is on. it comes on and off sparatically. my passenger front wheel bearings were so bad they ruined the ABS sensor and replacing it turned the light off. the other side might have got to that point. The auto parts store said they can not tell what wheel it is coming from. they didnt scan it though. ordering wheel bearing and sensor today seeing if that fixes it.

i also have a check engine light on for evap control circuit. dont think its related but thought id throw it our there.

 

and that soft crunchy spot only happens on the first stop and its like at the 1/2 pedal mark then goes away. its hard to explain, but the pedal actually feels crunchy. not just soft.

 

also probably unrelated. my truck had the tin can with ball bearing shaking sound. first thougt it might be wheel bearings. i run offet wheels. determined it has the hub actuators. i plugged the vac line at solenoind. so now the front axels always spin. i already replaced the solenoid, check valve and hub actuator years ago. will this hurt anything other then mpg?

 

Offset wheels put an excessive load on the wheel bearings. It sounds like you need to do a a COMPLETE overhaul of your wheel and brake system starting with the wheel bearings. If you don't KNOW what you're doing then you need to take it so someone that does before you kill yourself, your girl friend or somebody else.

It sounds like you have a bad master cylinder and also problems with the ABS AND with the wheels bearings. There's too many things going on with this truck for a novice to try and repair it IMO. And before you decide to ignore my advice, keep in mind that it you get into an accident you could be FELONY liable since you knew that there a multiple problems with your brakes. And if somebody gets killed or injured then you're going to be looking at prison time.

PS that soft crunchy feeling that goes away sounds like another bad wheel bearing to me. But they shouldn't cause the brakes to fail, at least not immediately. You've definitely got multiple problems here.

 

The brakes on a Pontiac Sunbird I bought for my daughter was doing something similar after an accident on the right front. The dealer shop diagnosed it as a bad ABS sensor on the right front wheel.

 

Don't drive it.
That is how one might describe how a brake pedal feels when the ABS is kicking in ..... that's how fast the ABS will release and reapply a brake or brakes. Likely related to the light and a bad sensor.

I agree with those who say the truck needs to be looked at by a mechanic schooled in ABS systems. May have other problems with ABS as well. No way would I be still driving it until fixed though.

A trooper's next door neighbor once had an intermittent brake issue .... and kept driving .... then one day the same trooper got a wreck call and responded and found that the his neighbor's brakes had failed (pedal would go all the way to floor) and that he passed a stop sign running into a 4 lane highway and struck a passing car. He was lucky as he hit the other car in right rear corner spinning it out with both ending up in a ditch in a median and no injuries. The neighbor accepted his RD ticket. Would have been cheaper (and safer ... and no points on MVR) to have just fixed the brakes.

Back in 1991 we got our first police cars with ABS, '91 Caprices. Before then a trooper might be riding along in the left lane and signal and hit your blues momentarily to warn those behind .... and brake hard to dart into a median crossover so as to not back up traffic or slow it .....
.... but the edge of the interstate often has a rough edge to it, maybe pot holes. Tires still bounce and air born tires have zero traction. With the new ABS '91s ... you'd be going along and stab the brake to quickly slow for your crossover at 65 mph, be slowing hard and suddenly as the left side tires dropped off pavement ... you'd feel that roughness for a split second and brakes would release and grab again and sometimes the car felt like it lost brakes. In a learned habit, an old school trooper would release and reapply his foot and many did not like the ABS.
Those cars had a single rear sensor on the differential and rear drums ..... so in reality .... for a split second each time the ABS computer released the momentarily slowed air born left side tires .... it was releasing three brakes and only the rt frt was constantly applied. I was only a third the way through my career .... not as old school as a man who had 25 years under his bat belt. In time, the newer cars got 4 wheel disc and 4 sensors and the guys adapted and learned to love the ABS.

I tell you that not to say that you or your fiancee are doing anything wrong (well ....other than maybe driving it) .... but to illustrate how a sensor can lead to the ABS kicking in and releasing and reapplying as if on a slick surface .... when you aren't. The ABS brain only knows what a sensor does or doesn't tell it. Whether the wheel is really slowed because of loss of traction ... or if it's a bad signal, the ABS brain doesn't know.

 

I get the feeling there is something more wrong with the ABS system. I've had trucks with a bad sensor on one wheel. It meant the abs wouldn't work. Your description sounds like the abs is not allowing any pressure to the calipers, something that requires a professional to look at. I'll repeat that a parts store does not have a scanner capable of reading the abs system

 

if the new wheel bearing and sensor dosnt fix it, i am going to replace the master Cylinder and bleed all the brakes. Maybe check Vacuum. after that ill be forced to take it the dealer with a tube of KY.

the ABS light can only come on for so many things...

Its odd it only happens at the first stop, and only sometimes.

 

Why the dealer? Why not a good independent shop that specializes in brakes and front end work?

 

A dealer is not your ONLY option, many shops have the tools and expertise to diagnose your truck.

 

A agree but no matter where you take it, make SURE that the mechanic that does the actual work (not the slick, front counter salesman) knows what he's doing and it isn't some zit faced kid that's never worked on a car before. Independant shops and the stealerships are both full of unqualified parts changers.

IMHO ABS isn't causing the "crunching" that you describe. ABS shouldn't even being engaging in a normal braking situation. And when it does, you should only feel a pulsing sensation. That's not to say that you may not have a problem with ABS but IMO you have a more basic braking or wheel bearing problem.

 

pretty sad id rather die then go the stealership. they wanted $5600 to fix a head valve and charged me $1700 on an $3 OD band servo snap ring. they dropped the tranny when they probably only needed to drop the valve body. swore they had no idea about the problem when theirs a multitude of reported cases. https://www.f150online.com/forums/tr...roke-pics.html -16 pages
also got burnt on a warranty with them.

pretty confident its Wheel Sensor or MC. when i start the truck the ABS light is not on, its possible that when i do the first stop is when it finds the fault and gets confused. that explains why it only happens within the first minute of driving. i havnt noticed if thats when the light pops up

my bearings and sensor come in tuesday. ill keep yall posted. hopefully it can help someone in the future.