Wierd brake problem '96 ford windstar

I have a '96 ford windstar (3.0V6)the brakes have worked fine in the 6 mo. i’ve had it but now after driving on the hiway for a few miles,the brakes ‘self apply’. they will start to drag until there is absolutely no free play in the pedal. driving around town they’re fine, but hiway driving without using the brakes seems to cause them to self apply…the calipers aren’t stuck. any ideas would be a great help, thanx

Have you taken this vehicle to a mechanic?

I’m going to suggest a problem in the brake master cylinder, possibly the vacuum booster. This assumes all four brakes are working correctly and not dragging.

Are there any other symptoms that go along with this?

Do you use the parking brake? If so, does it function normally and release completely?

I haven’t taken it to a mechanic, as this type of problem is well beyond the realm of most local wrenches, so a dealer & a proper scan may be in my future. My suspicions were first with the vacuum booster or perhaps a lack of pushrod clearance between the booster & master cyl. Other symptoms lead me to think the problem is only with the front discs, and when this problem happens, it almost seems like the brakes are ‘pulsating’ leading me to believe that perhaps the problem lies in the ABS system. I have yet to scan the ABS. but the light has always been on, the previu=ous owner had it checked & they told him it was a rear wheel sensor & not to worry.Other than that, the brakes work superb, and no i never use the parking brake on automatics, because they do tend to ‘stick’ after non use. but thanx for the info mc

Oh. You didn’t mention the ABS light in your original post. That changes everything. You need to find out why the light is on. I would NOT take the previous owner’s word for the cause.

Yes, it seems like a scan of the ABS is next,and depending on the results,i will replace the defective parts (within reason) or possibly disengage the entire unwanted ABS if that proves to be the problem.///thanx again MC