Rear wheel blocks, however RABS should prevent it. Why? - Ford Truck Enthusiasts Forums



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Rear wheel blocks, however RABS should prevent it. Why?

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Old 07-07-2014, 03:16 PM
E150 4.9 1990 E150 4.9 1990 is offline
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Rear wheel blocks, however RABS should prevent it. Why?

It's a 96 E250. ABS light is not on. After ignition 2 sec. and light goes out. So the unit thinks it is everything alright. But it's not. When Braking hard, rear wheels block and I have to keep the van straigth not to come off the road...Sometimes funny, sometimes it's not.

How irt began: Rear drum was warped. Corrected by a machine shop, new pads and cylinder mounted. I thought it's ok. It was good for a while. Then it started to seize. I got off the brake but the van doesn't start to roll. Only if I pushed the throttle. Ok I check the rear axle, it is hot. Fine. Drum controlled it is warped again. Fine. Cold no seizing. Logical. The diameter differences became too big at different points of the drum and the self adjuster adjusted himself to the biggest diameter of course. So at the smaller diameter areas the pads rubbed the drum = overheating again. But where comes the diameter difference? I think the rear brake works with too big performance. The front brakes should do 70% of the braking job. If so the rear drum never overheats. We rebuilt then the front brake because we thougth there can be some mechanical problem with it ( there was, the pistons where disgusting ). When I brake hard the rear blocks still. Tomorrow I will check the front and the rear brake performance so we will know how they perform. Maybe the result will be good and the rear drums won't be overloaded in future and no warping will come but the blocking wheels still make me nervous.

There is the damn ABS and it blocks. No codes. No ABS light on. What's going on there?
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Old 07-08-2014, 06:14 PM
jimandnena jimandnena is offline
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Quote:
Originally Posted by E150 4.9 1990 View Post
It's a 96 E250. ABS light is not on. After ignition 2 sec. and light goes out. So the unit thinks it is everything alright. But it's not. When Braking hard, rear wheels block and I have to keep the van straigth not to come off the road...Sometimes funny, sometimes it's not.

How irt began: Rear drum was warped. Corrected by a machine shop, new pads and cylinder mounted. I thought it's ok. It was good for a while. Then it started to seize. I got off the brake but the van doesn't start to roll. Only if I pushed the throttle. Ok I check the rear axle, it is hot. Fine. Drum controlled it is warped again. Fine. Cold no seizing. Logical. The diameter differences became too big at different points of the drum and the self adjuster adjusted himself to the biggest diameter of course. So at the smaller diameter areas the pads rubbed the drum = overheating again. But where comes the diameter difference? I think the rear brake works with too big performance. The front brakes should do 70% of the braking job. If so the rear drum never overheats. We rebuilt then the front brake because we thougth there can be some mechanical problem with it ( there was, the pistons where disgusting ). When I brake hard the rear blocks still. Tomorrow I will check the front and the rear brake performance so we will know how they perform. Maybe the result will be good and the rear drums won't be overloaded in future and no warping will come but the blocking wheels still make me nervous.

There is the damn ABS and it blocks. No codes. No ABS light on. What's going on there?
Hi,
My '88 E150 doesn't have ABS but my '92 F150 did, might be similar.
I sounds like pressure in the rear brake lines might be holding pressure on the rear drum? If I remember correctly (always a danger), there is a proportioning valve on the master cylinder. It may only be on the pickups? I replaced the master and got that valve in wrong and it locked the rear drums. If that valve is malfunctioning, it could hold pressure.

Sorry I don't know more about it, just that small bit of experience.
jim
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Old 07-12-2014, 01:18 AM
OSHS OSHS is offline
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I don't know about the earlier vans, but on my 2001 15-passenger, even with the V-10 up front, the rear is significantly heavier than the rear. I have never weighed it (each axle, that is), but the effort to raise it via a floor jack is 2x for rear.

As for your van with rear drums, there is a valve, either part of the MC or in the rear lines that is designed to keep a little pressure on the shoes. This is a feature of rear drums. I'm too young to remember where it is located.

If you jack up the rear axle and cannot turn either wheel, you have a problem. That valve is suspect, especially if you cannot freely turn both wheels. Before you go hunting for that valve, make sure the emergency brake is adjusted properly. Beyond that, a flexible brake line could be collapsed (read: old) and causing drag. Drag causes heat, heat causes warping.

On the plus side, I just did a friend's rear brakes on a 2005 Buick Park Ave. She had worn the rotors paper-thin and required new calipers. The pistons were over extended and sitting cockeyed. Oh, and she showed up to the house with the brake light on (dash light, meaning low fluid). The rotors were literally paper-thin. Never seen anything like it before. At least not in person. New calipers, new rotors, new pads.
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Old 07-12-2014, 05:26 AM
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Originally Posted by OSHS View Post

On the plus side, I just did a friend's rear brakes on a 2005 Buick Park Ave. She had worn the rotors paper-thin and required new calipers. The pistons were over extended and sitting cockeyed. Oh, and she showed up to the house with the brake light on (dash light, meaning low fluid).
Not trying to sound too sexist or disrespectful to the other gender but they can and do occasionally run a vehicle long past time to have it repaired or even inspected. In fact I've heard a few more colorful mechanics cite "wimmen---could screw up a junk yard with a Q-Tip.................." I can't disagree, having once owned a body shop.

It would seem some believe the warning lights are merely suggestions, not necessarily all that important. Of course some men are just as guilty of the same thing.
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