Weird Brake Pedal Sensation

[tate]

When I apply the brakes in my 06 explorer the pedal does not descend smoothly. Its almost like the piston in the master cylinder is chattering as it moves. Has anyone ever experienced this? Does anybody know what could be causing this? What are the fixes?

 

[matsavol]

I believe I'm having same or similar issue: When the car is hot the brake pedal makes "snaring" sound, like if there was a piston with a dry rubber O-ring forced to move in cylinder. If I press the pedal completely to the floor and then release, the sound is gone for a while. I applied some CRC to the brake pedal rod that enters to the firewall through some foam cushion. I think this did improve the situation, while not completely gone.

 

[tate]

Exactly

The symptoms you describe are exactly what I am experiencing. I will try getting some silicone in there.

 

[matsavol]

That's what it was

OK... after driving few more days the situation has improved so that I call this issue fixed in my car.

 

[midiout]

Inside or outside of the car ? I would presume in the driver's compartment, not the engine firewall ?

 

[tate]

A little of both

The sensation is felt through the brake pedal.

When you go to lubricate the pedal I passed a tube between the foam and the rod the connects the brake pedal to the head of the piston and sprayed silicone lubricant in there.

The vibration seems to be taking place in the engine compartment where the brake piston is chattering on the inside of the cylinder as it is depressed.

 

[matsavol]

It's back...

This issue has come back after a year... but that's not much a surprise considering the quick fix. It seem certain that the brake fluid temperature has big effect on this since if the car is cool the brake pedal feels smooth. If the car has been driven a while and the engine compartment (and brake fluid) is hot, the issue comes up.

I'm pretty sure the issue is with the master cylinder and the hot brake fluid not acting as good lubricant. Maybe if I let a shop replace the brake fluid with new better quality one it should help? Any suggestions? Or is it waste of time/money to even try this?

I think there was some service bulletin for this. My X is already out of warranty, so I doubt they will fix it for free. (Maybe have to wait if they ever recall this?)

 

[matsavol]

Brake fluid change: feels better

This issue has come back after a year... but that's not much a surprise considering the quick fix. It seem certain that the brake fluid temperature has big effect on this since if the car is cool the brake pedal feels smooth. If the car has been driven a while and the engine compartment (and brake fluid) is hot, the issue comes up.

I'm pretty sure the issue is with the master cylinder and the hot brake fluid not acting as good lubricant. Maybe if I let a shop replace the brake fluid with new better quality one it should help? Any suggestions? Or is it waste of time/money to even try this?

I think there was some service bulletin for this. My X is already out of warranty, so I doubt they will fix it for free. (Maybe have to wait if they ever recall this?)

Quoting myself... I did today the brake fluid change myself. I was shocked that how black the old fluid was! I have never changed the brake fluid on this X, so it was about time? I have less than 30K miles on this but I guess not only miles but time too takes its toll.

I haven't driven anywhere yet but at my parking lot. First impression on the brake pedal feel is much smoother... I'll post back after few days.

 

[matsavol]

Problem solved!

OK. So after couple days of driving I can tell the brake pedal feel is now butter smooth. Seriously, I couldn't have believed the brake fluid change could have made such a difference.

Anyone with the same symptoms I highly recommend this simple and inexpensive fix. Good luck with yours.