Crown Vic antilock brakes

[rlauzze]

93 Crown Vic with only 50k miles. Really nice car, but... After warming up, and about 20 miles, car vibrates severely, like severely out of balance tire, or missing lug nuts. Car is nearly undrivable when vibrating (starts slowly, then builds till cowl shakes severely). Only does it after warmed up; goes away after sitting approximately an hour. Seems to require more gas pedal to keep up speed. Does it whether brakes applied or not. Suspect antilock brakes or traction assist pulsing on one or more wheels while cruising? Just spent $1400 for brake flush, new rotors, etc, and misc other stuff, but didn't help. Any ideas?

[dcolemanslaw]

Originally Posted by rlauzze

93 Crown Vic with only 50k miles. Really nice car, but... After warming up, and about 20 miles, car vibrates severely, like severely out of balance tire, or missing lug nuts. Car is nearly undrivable when vibrating (starts slowly, then builds till cowl shakes severely). Only does it after warmed up; goes away after sitting approximately an hour. Seems to require more gas pedal to keep up speed. Does it whether brakes applied or not. Suspect antilock brakes or traction assist pulsing on one or more wheels while cruising? Just spent $1400 for brake flush, new rotors, etc, and misc other stuff, but didn't help. Any ideas?

I have a 92 Crown Vic and I have a problem with the front brakes not releasing. Your problem sounds like mine. Check and see if you can pull back on your brake pedal with your foot the next time this occurs. Sounds like your brakes are not releasing. I replaced the front calipers, master cylinder, and turned the rotors with no sucess. It worked fine for a little while after I replaced the master cylinder. I don't have a clue what is causing this. If you find out something, please let me know. I do know this, because the front brakes aren't releasing the rotors are getting warped. Because the rotors are warped you will get vibrations. And over a period of time, this will result in other problems. I had to replace the lower ball joints. There is a power booster that is left for me to replace. I guess I will do that next.

[jimmytroanoke]

Originally Posted by dcolemanslaw

I have a 92 Crown Vic and I have a problem with the front brakes not releasing. Your problem sounds like mine. Check and see if you can pull back on your brake pedal with your foot the next time this occurs. Sounds like your brakes are not releasing. I replaced the front calipers, master cylinder, and turned the rotors with no sucess. It worked fine for a little while after I replaced the master cylinder. I don't have a clue what is causing this. If you find out something, please let me know. I do know this, because the front brakes aren't releasing the rotors are getting warped. Because the rotors are warped you will get vibrations. And over a period of time, this will result in other problems. I had to replace the lower ball joints. There is a power booster that is left for me to replace. I guess I will do that next.

Brakes not releasing is not a booster problem. Have you ever replaced the rbber hoses at the ends of the brake lines to the calipers? The rubber brakes down internally and it will quite often act like a one way valve, IE: not allowing the fluid to flow back and release the brakes. Remember your vehicles are 12-13 years old. They may look fine on the outside, but rubber deteriorates! These are one of the most often overlooked components of a car until they burst and cause a no brakes situation and accident. I recommend replacing them on any car at 10 years or 100k miles. They aren't expensive and easy to change. Bleed your brakes thoroughly after. After driving the car and getting stuff hot to where the brakes seem to be binding, pull it in your driveway, jack up the car, and see if the wheels spin freely. If you find a wheel that is binding, loosen the hose at the frame end. If it loosens at this point it is the master cyl. If not, then break the line loose at the caliper or the bleed nipple. If the wheel immediately loosens and spins the problem is the hose. If the wheel does not loosen then, it is the caliper.

[dcolemanslaw]

Originally Posted by jimmytroanoke

Brakes not releasing is not a booster problem. Have you ever replaced the rbber hoses at the ends of the brake lines to the calipers? The rubber brakes down internally and it will quite often act like a one way valve, IE: not allowing the fluid to flow back and release the brakes. Remember your vehicles are 12-13 years old. They may look fine on the outside, but rubber deteriorates! These are one of the most often overlooked components of a car until they burst and cause a no brakes situation and accident. I recommend replacing them on any car at 10 years or 100k miles. They aren't expensive and easy to change. Bleed your brakes thoroughly after. After driving the car and getting stuff hot to where the brakes seem to be binding, pull it in your driveway, jack up the car, and see if the wheels spin freely. If you find a wheel that is binding, loosen the hose at the frame end. If it loosens at this point it is the master cyl. If not, then break the line loose at the caliper or the bleed nipple. If the wheel immediately loosens and spins the problem is the hose. If the wheel does not loosen then, it is the caliper.

Thanks, I haven't thought of that. I will try this out and see if the brake line is the culprit. I would think that this is the problem because I have changed the calipers and master cylinder already. I will let you know!

[rlauzze]

I hadn't thought of that either. Mechanic said valve body may need replaced because code set in computer pertaining to left front ABS inlet valve reference voltage signal. Also said very expensive! Had brake system flushed also because of soft brake pedal AND pedal approached floor when pumped. Never failed to stop the car, just too near the floor. Pedal approaching floor somewhat better, but still a soft pedal, in my opinion. The rubber hose end issue fits with the soft pedal. I had master cylinder replaced last year, with no change. Tried today to get it to vibrate, but it was just fine. Never acts up when you need it to. Thought I'd pull the ABS fuze when it was vibrating to see if that made any difference. Gonna look into the rubber brake hose issue - someone bound to make stainless ones.

[jimmytroanoke]

Also beware that if you have had your master cyl. replaced, the shop better have had the correct diagnostic scanner to bleed the brakes. Without a scan tool that can manually operate the ABS unit, you will never get the air out of it no matter how many times you bleed it at the wheels.

[dcolemanslaw]

Originally Posted by jimmytroanoke

Also beware that if you have had your master cyl. replaced, the shop better have had the correct diagnostic scanner to bleed the brakes. Without a scan tool that can manually operate the ABS unit, you will never get the air out of it no matter how many times you bleed it at the wheels.

I replaced the master cylinder myself. I just bled the brakes. I didn't use a scanner. What and how does this diagnostic scanner work? Is there a way to get around using the scanner? Maybe disabling the ABS system? I have never heard this. Thanks for the info.

[jimmytroanoke]

This is the service manual procedure for a 95 model. I am sure yours is similar. Basically the unit needs to be commanded to open all the valves so no air gets trapped. No way around it.

With Antilock Brakes

The master cylinder and hydraulic control unit must be bled using ABS test adapter T90P-50-ALA. If this procedure is not followed, air will be trapped in the hydraulic control unit which will eventually lead to a spongy brake pedal.

To bleed the master cylinder and HCU, disconnect the 55-pin plug from the ABS module and install the ABS test adapter to the wire harness 55-pin plug.


Place bleed/harness switch in bleed position.
Turn ignition to ON position. At this point the red OFF indicator should turn on.
Push motor button on adapter down to start pump motor. The red OFF indicator should turn off and the green ON indicator should turn on.
Pump motor will run for 60 seconds once motor button is pushed. If pump motor must be stopped before 60 seconds, press abort button to turn motor off.
After 20 seconds of pump motor operation, push and hold valve button down for 20 seconds then release.
Brake lines may be bled in the conventional manner. Ensure lines are bled in the following sequence:



Right Rear.
Left Front.
Left Rear.
Right Front.

[rlauzze]

Now I'm confused. Don't have a Ford CV manual, but using a Clymers. I thought you could bleed the brakes conventionally if you were careful not to let air enter (thru the master cylinder). That means I have to take the car to a dealer or a well equiped garage to get the brake hoses replaced? (That's why I took it to a garage to get the brake system flushed, I suspected air in the hydraulic controller - soft pedal and severe vibration when driving after 20 miles or so. That didn't fix the problem, and that's why it makes sense that brake hoses could be the problem.)

[jimmytroanoke]

Originally Posted by rlauzze

Now I'm confused. Don't have a Ford CV manual, but using a Clymers. I thought you could bleed the brakes conventionally if you were careful not to let air enter (thru the master cylinder). That means I have to take the car to a dealer or a well equiped garage to get the brake hoses replaced? (That's why I took it to a garage to get the brake system flushed, I suspected air in the hydraulic controller - soft pedal and severe vibration when driving after 20 miles or so. That didn't fix the problem, and that's why it makes sense that brake hoses could be the problem.)

The procedure above is for replacing the master cylinder or abs unit. For working at the wheels you can bleed conventionally. Just don't let the master cyl go dry! And don't leave lines disconnected for an extended period as air could migrate upwards to the ABS unit.