I have a big problem with the brakes on my 90 4x4. I've recently started getting the 'brake' warning light and 'rear antilock' warning light at the same time. When this happens, the pedal feels different. My rear drums are grabbing when I hit the pedal and not releasing. The truck will actually come to a stop from the friction on the rear wheels. Front brakes are fine.

I can let the truck sit for a while, start again and the brakes have released. Today they locked up so tigh that I could not drive the truck. I was able to slowly get it home (less than a mile) and I am not going to drive it until I get this fixed. It's just not safe.

Anybody know what is causing this? Is this the Master cylinder?

 

It sounds like you have two problems. The brake light is from a low fluid level in the resevoir. The ABS problem sounds like the ABS valve itself is gummed up inside. I've seen this happen on a ranger. The rear brakes would engage, and the ABS valve was so gummed up that it wouldn't let the shoes back off enough. They would heat up and fade. It sounds like your problem is a little worse.

The ABS valve may be leaking which would cause the low fluid, you may have a leak elsewhere in the system, or your front pads may need replacing.

You're right not to drive it until it's fixed. If you're not comfortable tackling this problem, I'd take it someplace you can trust. Either way, it's likely to cost a few bucks to fix.

 

I don't know if this holds in all cars with ABS but a mechanic once told me that if you change brakes on an ABS vehicle, you should not push brake fluid backwards through the brake lines. You know how you do that when you have to plunge the hydraulic cylinders in order to make room to get the new pads on the disk? He said to open the bleeder valve and then plunge the cylinders. That way the fluid exits the vehicle versus going back through the brake lines. He said that would damage the ABS somehow. It's an easy enough thing to do. Just thought I'd throw that in there.

 

Thanks for the response guys. I don't have low fluid though.

Can you tell me where the ABS valve is? If it is gummed up can it be cleaned or does it have to be replaced?

 

Can you get any codes from the ABS test connector? I've had the red Brake + amber ABS warning lights illuminated on again-off again for nearly a year, and picked up a code 4 ( I think its the ABS valve itself - I'd have to check the Haines manual again).

Since my braking is Ok other than the loss of ABS I'm living with it for now.

-rlp
1989 F150 XLT Lariat, shortbed 351w, C6 auto trans.with RABS I

 

The ABS valve is usually a big ole thing with a bunch of brake lines running in and out of it mounted in the engine compartment on the drivers side fenderwell. I know nothing about it though.

 

I've also seen it mounted on the inside of the frame near the bellhousing under the master cylinder. Just follow the brake lines.

You can *try* taking it apart and cleaning it, but results will be much better if you replace it. And then take it to a shop and have them powerbleed it. Old fluid is the reason it failed to begin with.

 

It sounds like it could be rabs valve mounted on frame under drivers side. You can get codes out of this system by grounding out wire and counting flashes of abs light in dash and go to shop manual for proper pinpoint test. I don't think it is making rear brakes grab possibly wheel cylinders or ebrake hanging up.
BB1

 

well BB1 got it right - it is called a rabs valve - you will have either rabs 1 or rabs 2
rabs 1 has the test socket on the driverside firewall under the dash and rabs 2 has it hidden behind the glove box ( usually ) the rabs valves are notorious for failing and not cheap to replace, since you have the red brake light on also it means that you had a loss of pressure at some point - hows the master ,did the pedal ever hit the floor when you were braking ,does it sink with steady pressure applied .

first i would pull the rear drums and see what you notice , if nothing is obvious then pull the codes .

you could also try pulling the fuse for the anti locks and see if this helps if so chances are its the rabs module and not the valve -since pulling the fuse wont disable the valve it will just work like a standard proportioning valve- if it works better - now decide if you really want anti locks i have a f350 w/suspension upgrade to 6800 kg gvw - we all have pulled the anti lock fuse becuase it tended to increase stopping distances when we didn't want it to - and when loaded on gravel roads it was terrible - always setting off the abs at the slightest movement - we all feel safer driving without the abs

 

Russt:

Hey--could I trouble you to go read my dissertation under the '87-'96 forum, entitled "Spongy Brake Pedal?" Because I have a question about the RABS valve. Is that right inside the frame rail, just about directly under the Master Cylinder? Because I don't have the "bleeder rod" in what I thought was the proportioning valve on my '88 F-150. It just doesn't have one.

I'm thinking that what I thought was just the proportioning valve MUST also be the RABS valve as well, because I replaced the hyd. line to the rear, and there IS no other valve that would/could activate rear ABS.

So the RABS must also incorporate the standard proportioning/differential valve which would normally be found on a truck with no abs, right?

What's beginning to concern me more than the spongy pedal is the fact that the red BRAKE light is not coming on when I turn the ignition on, though all the other idiot lights do, including the ABS light. Yet the red BRAKE light comes on when I push the E-brake, at least, most times it does, so the bulb can't be bad.

Shouldn't the red BRAKE light come on with the other idiot lights, then go off after two seconds?

Also, I bled the bleed nipple on the RABS/proportioning vavle (if that's what it is). Was I not supposed to do this?

Re: the order, I did it first, before going: RR, LR, RF and LF. Actually, in the very first bleed, I also came back to it again, I believe, after doing the RR, but I only got air out of it the very first time I bled the nipple on the proportioning valve.

Just wondering if my MS is bad, and why the red light isn't coming on, and WTF I'm supposed to do with the bleed nipple on the proportioning valve, and in what order, wheelwise. Oh, and what I'm supposed to do since there's no "bleeder rod" on my proportioning valve-lol.

My Haynes manual is supposed to cover 1980 - 1991, but it NEVER mentions ABS of any sort, and shows only a proportioning vavle with a bleeder rod--arrgghh!!

Thanks in advance.

Peter

 

Hey--just wanted to shamelessly "bump" this post, in the hope that I will get answers here, or in my much more detailed post (that I started, myself) called "Spongy Brake Pedal". The g.f. is taking her car out of town, for the holidays, and I must repair my truck to go ****** my old boat, before the River freezes, so HELP! LOL1

Peter

 

yeah thats a rabs valve , it is (except for some electrical switches )the same as a standard proportioning valve,the rabs module under the dash controls it - they fail more oftenn than a standard valve and usually fail by either allowing your rears to lock hard or they activate the antilock feature too early and prevent the rears from doing thier job under normal or light braking - that will give you some excess travel in the pedal becuase your now pushing harder to compensate for the lack of normal stopping power .

red light needs to be fixed though so that you can see if you indeed have some kind failure ,the park brake and brake pedal are on 2 different switches so that would explain why it lights on one and not the other - check the wiring back to the valve. also do your brake lights work and do they come on at the lightest touch of the brake pedal or do they come on at like half pressure - check with the truck running and e brake off ,the timing of the brake light switch plays a big role in the rabs system.

to check your master step hard on the pedal - does it hit the floor , keep holding pressure and notice if it drops at all .either of these /change the master


old dirty black brake fluid means water and that cuase spongey brakes - bleed it til its gone,

check rear brake adjustment - do a manual adjustment and pull the drums off to see if the self adjusters are working and that the adjuster cable hasn't snapped .

other problem areas for these trucks are firewall flex -around the booster too ,the booster itself / master if they are origonal , ford had some recalls on wagner brake products in late 88/89 -components would partially fail giving a flase pedal feel - not that usuall ford solid feel on the brakes -

other than that looks like you did everything right , all i can say is i own an 88 302 4x4 ,and have driven friends -same years etc. and they all don't have that solid ford braking feel - probably becuase alot of these trucks never went in for those recalls - something to consider if nothing else corrects it.


holler back if u have any more questions

 

Hey Dog :-))

I had a simular symptom on my 94 f150 with the rear seeming to grab for no reason but only when I went forward about 10ft then it would kick in. It was very perplexing and it wouldn't do it all the time but maybe 3 out of 5 times and would seem to go away when I drove it for a bit. So I suspected tranny, rear end, or ABS.

In testing I waited until I had a good day to climb under the truck and when it did it I drove it for about 20 minutes to get things good and warm, Climbed under the truck and felt the rearend. It didn't seem bad, warm but not hot. Felt the tranny, again it seemed ok and the fluid was fine. Checked the left rear hub at the tire and it was warm. Checked the right rear and it was warm, but much cooler than the left side. So thats when I took it back home and pulled the rear drum. And what a chore it was to get that drum off...

From what I found was that I had a problem on the rear drivers side where the pad had broken and peices had seperated from the shoe. When I did the brakes (incl all new hardware) when I got to the pass side I noticed that the pads seated much better than the drivers side had. In jacking the whole rear an looking into it I found that the emergency brake cable on the drivers side had not released the last inch or so. You can look on the outter frame, up about 2 ft from the rear axle, and see a metal braket that connect the e-brake pedal wire to the 2 rear drum wires and mine was sitting crocked. it should be straight up and down. I used a crowbar and got it released fully and the pads seated nice like they're supposed to.
Needless to say that this fixed my problem and , for all you odd clunking noise from the front end people, it solved my clunk too - just don't ask me why. I woulda swore that clunk was coming from the front...LOL

I hope this little narative helps!
Popa Tim