njb73

Hi guys,

I have a Grand Cherokee overland 4.7 v8 2002

Just had a problem where i was coming to a stop from about 10mph, put my foot on the brake, the engine revved , felt high tension on brake peddle and as it was not slowing down pressed harder but brake did not do anything...Jeep went straight into my house wall...

After much head scratching and wondering WTF... Took it out for a test in the field at the side of the house and all working well..

No my foot was not on the gas at the same time... I was literally full weight onto the brake pushing back in the seat to no effect...

Just no movement in brake peddle

Any ideas Guys

wingless

Welcome to the forum.

That sounds scary. Glad nobody was hurt.

The NHTSA has a spot to report this type of problem.

The campaign number 06E022000 is the only one currently listed for that vehicle's braking and doesn't appear to be applicable.

Use your insurance company and the dealership to address the problem.

The most common root cause that is identified is driver error. A driver under duress presses the gas pedal harder and harder, thinking they are pressing the brake, wanting more and more to brake, so they press harder and harder, until the vehicle is stopped by an object.

The best solutions to this problem are to use the ignition key to turn off the vehicle or the gearshift selector to move it into neutral.

njb73

Hi, if i had been pushing the gas pedal to the floor a) It would have went through the wall instead of coasting into it b) The peddle would be on the floor instead of having a high tension on it

I am thinking more along the lines of the brake booster

dave1123

That was going to be my assumption as well. It sounds like a sudden vacuum dump which caused the engine to increase rpm and the loss of brake boost. If the diaphragm had ruptured, it wouldn't act normal later. It's probably the seal around the pedal rod. With that, the harder you press, the more it leaks. You should be hearing a whistle from under the dash when it happens and it may not leak unless it's a panic stop with a LOT of pedal pressure. BUT that's when you need brakes the most! Using that much pressure should have activated the ABS system.

In my opinion, replace the brake booster.

njb73

Just ran through a few checks for checking vaccum hose,check valve and to see if the booster can hold vaccum. Found the engine picks up slightly when brake cleaner sprayed over the check valve going into the booster.

So i maybe looking at loss of vaccum on the brake side with the vaccum and the hyd pressure causing such high tension on the pedal side.

njb73

But... on the drive home the brakes were working fine with many junctions upto the house... probably about 100yards from when i last used the brake until it happened...

dave1123

delete, irrelovent.

njb73

I would rather soften the rubber to prove something than have the brakes fail at 60

dave1123

Oh, I agree completely. I just thought you did that after you had the problem and it solved the sealing problem.