2002 Windstar Jackhammer noise under the hood

After 3 months of complaining my wife finally got me in the van to do some errands. We came to a stop at a stop light and I hear this jack hammer noise start, lasts about 3 seconds and trails off. I am looking around the instersection, which is underconstruction, looking for a jack hammer and my wife says that’s the noise that I have been talking about. This noise only occurs when the car is at a standstill after braking and recently happened twice when my wife stopped, released the brake and applied it again. The problem is getting progressively worse.Our mechanic’s opinion is that is is a rpm sensor on one of the wheels which is sending a false signal to the ABS system to activate. Another opinion is that the master cylinder has moisture in it and needs to be flushed.This car has about 125m miles. What so I try first?

I would go with the ABS theory. If the fluid has never been flushed, I would take care of that too.

Where does the noise seem to be coming from? Do you feel the brake pedal pulsate when you hear the noise?

The Exciter ring for the ABS sensor came loose on both CV axles on my wife’s 98 Windstar. Check underneath the van to see if the Exciter rings are in place. It was cheaper to replace the CV axle than to replace the Exciter ring on the original axle.

Ed B.

Thanks for the replys. The noise is coming from inside the engince compartment, up against the firewall, near center of dash. We had the CV joints redone on this car about 100K. Everything looks tight. No leaks or anything loose. My wife drives this car 99% of the time and she says there is no pulsating from the brake pedal. The noise is getting very regular and is starting to last the whole time the brake pedal is engaged. There is no metal sound to the noise, just a very loud knocking.

When you brake, are these normal or hard stops? What happens when you just slightly press the brake pedal, without really trying to decelerate at all?
I wonder if some sort of engine or transmission mount is loose or maybe just something that’s mechanically attached to the engine but is located close enough to the firewall.
Maybe that’s what’s clanging when it is trying to get to a stand still…

Isn’t the ABS unit mounted (attached) to the brake master cylinder? That would put it on the firewall, right in front of the driver. Sounds have a tendency to travel on solid metal, and be hard to locate. Since this is an '02, has the brake fluid ever been changed? Start with that. It’s an easy enough fix. If the ABS unit is getting mad at you (e.g., just dirty/old/contaminated fluid - which you can’t always tell just by looking), this may sort it out. If it’s not that, then you’ll have done the vehicle a necessary service, anyway.


problem with the torque converter? ie, when the wheels can’t move the engine is fighting the torque converter…

maybe try putting it in neutral as you are stopping and see if it doesn’t make the noise. that would tell you it’s not the ABS and that it is in the drivetrain.