It sound like your brake booster is sticking or that could just be me.
Well starting to sound more like you are right.
Got to do a little diagnostic time on it before work today. Engine off I could repeat the problem. It felt like it was in the peddle but you could hear the rear brakes squeak as it ovecame what ever is doing this. Did it 15 times or more. So I started juggling cars to get it up to the garage so I could tinker on it tonight when I get home. Started it and it happend. I pumped the brakes a few time and it stared getting less and less. Did a couple loops around the block hammering the brakes and its gone.
Drive it to work today and see if it comes back.
Basically it feels like your hitting the brakes with the parking brake on. Peddle high and hard because they are already up. Then suddenly it drops with a pop and you hear the rears activate.
Maybe I'll pull the check valve off the booster and see if I can shoot some WD 40 in there at the seals on the shaft and valve.
Any check valves in the load sensing junk?
I'll go through the back brakes Thursday and verify no problems back there and check the linings and adjusters. I plan to add a a leaf to each side that day any way to take care of a sag problem. Its daily hitting the bumps stops on the hwy EMPTY.
