Hi all. In reference to a 1991 F-150 2wd w/ 4.9 and M5OD:

Today it was raining, but not frozen. Just like the rest of you I drive in the rain a lot and I know what to expect. Driving through Central NJ today, I noticed what I think is the ABS making a grinding noise that I haven't heard it make before. The rear wheels locked when I put moderate pressure on the brakes, which I attributed to the rain and didn't think about too much. Later I was coming down a hill with a curve on it, and a car comes out in front of me from the left lane and brakes for a right turn. Couldn't stop in time and hit the back end of it at about 45 degrees. Turns out it was a girl I went on a few dates with, and she didn't seem pissed and insisted I hang up when I went to call the police even though it was mostly my fault. Anyway, driving home later (bad damage but still driveable, don't have pics cuz it's dark), I noticed the rear wheels locking up every single time I hit the brakes. I know wet roads are slippery, but they were locking up much sooner and more frequently than I've ever experienced, and were always accompanied by the ABS noise that I never heard before today.

So, is this a bad brake adjuster, or some fault with the RABS? I don't really know how the ABS works on this truck, but there is a small possibility it has an air bubble from when I replaced the brake lines last month. Y'all's thoughts?

 

58 views and no one has any thoughts yet? Rep to the first person who replies, even if it's Club Wagon. I know it's a rather stupid question but just lookin for random thoughts and war stories here.

 

You didn't mention anything about your antilock brake light coming on. Does it light when the ignition switch is on or in the start position?

 

Nope, never came on. I think it works because it comes on for a few miles whenever I mess around with the clutch pedal. Honestly, I forget if it comes on when I start the truck, but I'll check later. I know a lot of my idiot lights are either burned out or black-taped by the PO.

Thanks for the reply, rep has been left.

 

i can not answer ABS questions, because they were bypassed in my 88 when the truck was less than a week old. after getting a face plant on the windshield at a red light and then minutes later running a red light, and face plant at the next light, i went home and cut the abs out of the truck after ford said there was nothing wrong with the brakes.

23 years later, and the only problem in 493,000 miles besides replacing worn out parts was a bad master cylinder at around 250,000 miles.

 

Yeah, I disable the RABS on these trucks as soon as I get 'em. RABS is borderline dangerous IMO.

However, in your case, this doesn't sound like a RABS issue. With RABS, the problem I have is it reacts too quickly and won't lock up the brakes at all. Instead, the pedal drops toward the floor on hard braking, causing a quick rise in my heart rate.

I think yours sounds like a bad proportioning valve or perhaps you have a leak in your rear brakes (wheel cylinder or axle seal) and the brakes are grabbing.

 

The grinding noise suggest to me something isn't right with the mechanical parts of the rear brakes so I'd suggest you pull the drums and have a look.

 

Thanks, guys. Good stuff.

I'll check the proportioning valve. Also the rear brakes, as I don't have any good reason to definitively say they're good. But the grinding noise is definitely not coming from the brakes themselves.