Anti Lock Brake Problem

Ramblin Wreck · #1 08/05/07, 05:31 PM

I have a 99 Dodge Dakota that is mysteriously engaging the front brakes while travelling down the road. This happened first when Son #2 borrowed the truck, but since I wasn't in the vehicle (and he breaks things...a lot) I just assumed he had abused something. After the first episode, I replaced all the brakes, the master cylinder, and the calipers. It worked fine for a few weeks, but the same problem happened to me yesterday. It just started engaging the brakes and lugging the truck down. My guess is that something is wrong with the anti lock brakes, but that is just a guess. If any of you are aware of how I could confirm this, one way or the other, I'd appreciate the pointers. Also, if it is the anti-lock brakes, can they be easily disengaged or would this affect the rest of the braking system?

cfabe · #2 08/06/07, 02:59 PM

Pull the ABS fuse and that will disable the abs system... but if there is a mechanical problem in the ABS pump (sticking check valve etc) that may not resolve it. But that would the first thing I would try.

Does it engage the brakes suddenly or does it just gradually happen? Are there any sounds like you hear when the ABS is working during a stop on slippery surfaces (whirring, clicking etc)?

Rocky Fields · #3 08/06/07, 03:43 PM

Hey.

Here's a pdf that should be helpful:

http://www.i-car.com/pdf/upcr/procedures/br/br51.pdf

RF

Ramblin Wreck · #4 08/07/07, 08:58 AM

Thanks. I copied off the materials in the link, but I think I'll start with disconnecting the fuse. The problem occurs while traveling down the open road. You notice that the engine starts to lug down, and its due to the brakes engaging themselves. No warning lights come on when this happens, and I'm pretty sure there is an ABS light on the panel.

If I could be sure it was the anti lock brake control module, I'd just replace it and be done with it. But without a sure diagnosis, it could be like the master cylinder I just replaced, money spent to replace a part that was probably OK in the first place. And I'm still just guessing it is the ABS. I don't know of anything else on the vehicle that would engage the brakes while going down the road.

Thanks again for your advice.

Beeman · #5 08/09/07, 07:49 AM

I would just unplug the ABS control and see what happens. If it "fixes" it I would be tempted to just leave it unplugged and operate on non ABS braking but that's your call.

farminghandyman · #6 08/09/07, 09:44 AM

Is the return spring on the brake pedal intact, and hooked up?

Ramblin Wreck · #7 08/10/07, 08:29 PM

Quote:

Originally Posted by farminghandyman

Is the return spring on the brake pedal intact, and hooked up?

Yeah, the pedal seems to be working fine. The darn brakes just engage out of the clear blue sky while you're driving down the road. I'm going to see if disconnecting the fuse to the ABS solves the problem.

Beeman · #8 08/11/07, 12:07 PM

Quote:

Originally Posted by Ramblin Wreck

Yeah, the pedal seems to be working fine. The darn brakes just engage out of the clear blue sky while you're driving down the road. I'm going to see if disconnecting the fuse to the ABS solves the problem.

I have seen brakes stay applied due to a bad power brake booster. See if you can feel the brakes applied especially after braking and then remove the hose from the booster and see if they release. Apply brakes on a slight downhill and then place vehicle in neutral and see if it rolls freely, if not have someone remove the vacum hose from the booster and see what happens. Do the same test and see if pulling up on the pedal with your foot makes a difference, you can also try doing the test and shutting off the vehicle and see if the loss of vacum causes brakes to release.

Most ABS systems don't create pressure on their own, they can only pulsate the pressure that you have applied with your foot to the base brakes.

fixer1958 · #9 08/12/07, 10:04 AM

What about the hoses to the calipers collapsing.
Which brake location is the hottest after they start to drag.
I have personally had that happen to one of my vehicles
driving down the highway.......out of the blue.

Ramblin Wreck · #10 08/13/07, 01:25 PM

I disconnected the two fuses (one in the cab and one under the hood) that controls the ABS. The speedometer went out by doing that, so I replugged the one back in I had taken from the cab. That made the speedometer work again, and now I have warning lights about brake failure, which is what I expected. I'm going to drive it only for short trips in the near future to see what happens.

I'll keep in mind some of the other advice above. If it happens again (with the ABS disabled), I'll shut the engine off and see if that releases the pressure. That might mean the brake booster is going bad. If it were the hose collapsing to the calipers, would that "heal" itself when the truck is shut off? Any time there's been an episode, the problem has gone away after shutting the vehicle off.

Thanks for all the pointers.

Beeman · #11 08/14/07, 06:19 AM

Quote:

Originally Posted by Ramblin Wreck

I disconnected the two fuses (one in the cab and one under the hood) that controls the ABS. The speedometer went out by doing that, so I replugged the one back in I had taken from the cab. That made the speedometer work again, and now I have warning lights about brake failure, which is what I expected. I'm going to drive it only for short trips in the near future to see what happens.

I'll keep in mind some of the other advice above. If it happens again (with the ABS disabled), I'll shut the engine off and see if that releases the pressure. That might mean the brake booster is going bad. If it were the hose collapsing to the calipers, would that "heal" itself when the truck is shut off? Any time there's been an episode, the problem has gone away after shutting the vehicle off.

Thanks for all the pointers.

Yes, the pressure held by internally collapsing brake hose will relese eventually.

See if you can get the problem to happen. When it does you can try loosening a brake line at the master cyl. and see if there is pressure in the line. If there is pressure in the line then your problem is most likely the booster. If there is no pressure then open a bleeder screw, if there is pressure at the caliper and opening the bleeder screw releases it then look towards hoses. Be sure to start upstream first.

DrippingSprings · #12 08/14/07, 08:11 AM

If your brake rotors are below spec or the hoses are collapsing it can cause the brakes to do this

Ramblin Wreck · #13 08/14/07, 11:16 AM

Son #2 used the truck for several trips to the dump yesterday with no recurrence of the problem. Maybe disconnecting the anti-lock system worked, or maybe it is a renegade problem that will pick the worst possible moment to reappear!

foxtrapper · #14 08/15/07, 10:30 AM

Anti-lock systems don't provide pressure to the brake circuits, they release it. If the actuator were to turn on all by itself, the results would be nothing happening, as it released the non-existant pressure in the line(s). Remember, anti-lock brakes work by releasing the brakes when a wheel locks. They don't engage the brakes at all.

Now as I recall, wasn't there a problem with that era Dakota having a very similar brake pad to something else? Vendors got clever and started listing the brake pads as compatable with both, but they wouldn't work right on the Dakota. They would drag, heavily. Ford had this problem as well, with the F150 as I recall.

You say the brakes are engaging, but you haven't exactly described the symptoms. Do they gradually drag, worse and worse? Do the front brakes suddenly engage, slaming you face first into the dash? What are the symptoms?

Ramblin Wreck · #15 08/16/07, 07:40 AM

Quote:

Originally Posted by foxtrapper

You say the brakes are engaging, but you haven't exactly described the symptoms. Do they gradually drag, worse and worse? Do the front brakes suddenly engage, slaming you face first into the dash? What are the symptoms?

As you drive down the road, you notice that the vehicle begins to slow even as you apply gas to accelerate. The truck starts to lug down considerably, and it's due to the brakes engaging on their own. This happens on open stretches of road, not when you first start off from a stop. The problem has not reocurred since the ABS pump was disabled, but I understand from all the posts above plus yours that this may not be the cause of the problem.

cfabe · #16 08/16/07, 01:05 PM

Ramblin, from your description, I don't think it's the ABS. I had a similar problem on a chevy caprice. One caliper was hanging up slightly, and it would drag and get hot, which would cause it to drag more, get hotter, etc. Eventually I'd have to pull over and let it cool off, once had the rotor get glowing red hot and smoking.

When you replaced the calipers, did you take care to lubricate the slide pins and make sure they operated smoothly? On some vehicles they tend to get corroded and can seize up.

When it does it agian, get out and feel (carefully, might be really hot) the wheels so you can find out which break is dragging. Does the truck pull one way or the other when it happens?

Ramblin Wreck · #17 08/17/07, 01:35 PM

Quote:

Originally Posted by cfabe

When it does it agian, get out and feel (carefully, might be really hot) the wheels so you can find out which break is dragging. Does the truck pull one way or the other when it happens?

With me, it seemed to pull ever so slightly to the left, but just a little.