Brakes seem to give out when cold

[2000blackxlt]

Whenever I start and drive my Explorer, within the first 5 minutes of driving and stopping (for stop signs, red lights, turns) when I press the brake pedal to stop, I hear some type of "click" and the pedal goes almost to the floor, and I have to press hard to stop. Once that happens, it's fine...I can get my brakes back to normal. At first it always happened when I started the truck and drove, making a left turn and applying the brakes, then recently it happens when I'm coming to a stop from a straight away. This happens once after I start and drive the truck from a cold start it seems.

I checked the master cylinder reservoir and it was not low, although I topped it off (very small amount) and do not notice any brake fluid leaking from the engine or any of the wheels. I plan on checking around the master cylinder this weekend, but was wondering if anyone has any thoughts as to what could be causing the problem. I did have the dealer look at the brakes a few months ago (in for a non-brake related problem) but they said the brakes were fine.

When the truck is warm after being driven on the highway, it seems to be fine when I hit the brakes, or slow down and stop. Only seems to be when I initially start off in the truck and appy the brakes.

 

[Donner]

Welcome! Have you tried changing the relays/fuses?

 

[MustangP51]

Did you have the speed control switch recall fixed yet? If not it could be the switch leaking internally. This also could cause an under hood fire, even while parked.

 

[2000blackxlt]

problem found

appears when I disengage the speed sensor from the wheel, problem goes away. Reattach speed sensor cable - problem appears. Sounds like I need a new HUB (speed sensor not replaceable unless you swap out whole entire hub I'm being told)