I was driving around at lunch and started to notice that my brakes were loosing presure and had to push the pedal to the floor to get it to stop. I typically drive to a shady tree and eat lunch in the truck while its idling.

After letting it set for an hour or so I went out at 2pm break and checked the fluid level then started it up. The brake level was full and good pressure. Weird.

Its a 2003 4.6L V8.
Its very hot and humid here today almost 100 degrees so I had the A/C running too.


Any ideas on what it could be?
Its hard to fix something intermittently.

Thanks for any info.

 

Might outta look at your brakes for uneven wear. I've had cars do the same thing when the hardware sticks.

 

could be some contamination causing occasional internal leakage in the master cylinder.

If something gets under the seal it can cause a soft pedal, but then that "something" moves out from the seal and your pedal feels fine.

Perhaps try bleeding with fresh fluid to get it cleaned out.