94 F150: Over-sensitive brakes not tripping brake switch?

Hello all.

I picked up a 94 F150 (5.0 litre, auto, 2wd) this spring and have an unusual situation: the brakes are too sensitive! I barely have to touch them before the pedal goes down. It goes down about half way before there is any resistance. Odd thing is, the brakes work fine. (nice even skid patches on the street) Nice even braking.

At first, I thought air in the lines, so I bled them, twice. (a fluid flush couldn't hurt anyway..) On the off chance that the master is defective, I replaced that. No change. Replaced pads, shoes, drums and rotors. No change. (front calipers and rear brake cylinders were good, no leaks).

Is it possible for the brake booster to fail this way? Any other ideas?

The problem with all this is that the tiny amount of foot pressure on the brake pedal does not trip the brake switch. Thus no brake lites, and since I also tow a trailer with electric brakes, no brakes and brake lites on the trailer either. I'm worried that one day I'll be rear-ended by a semi...

Thanks in advance for your help. Mike

Reply to
Mike
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Dumb question: is it simply that the pedal/linkage is way out of adjustment? What you are describing sounds a lot like the correct behavior for the very top of the motion, assuming you don't get any braking until you feel resistance???

Good luck!

Bill

Reply to
Bill Schwab

I just replaced the booster on my CV for that very reason. At least it started that way and soon did not completely release unless iI lifted it with my foot. It wasn't too long that it would just apply the brakes as soon as I started to push the pedal. Wife damn near burn't the pads off it driving to the store. Called me complaining that car wouldn't move. She took it while I was out of town for a day or two. I guess I should have told her but, who'd have known she would have taken my car to the nursery for compost since she a perfectly good car of her own.

Lugnut

Reply to
lugnut

The brakes work almost right away. At idle and in drive, I need only push about 1/2 inch to stop the truck. If I we to puch till I felt resistance, it would be about the same as doing a PANIC stop.

Another test I tried was with the engine off, the brake is very firm, I could only push about 1/4 inch. I know that this is really just testing the spring inside the brake booster.

Thanks. Mike

Bill Schwab wrote:

Reply to
Mike

Try restricting the vacuum to the booster by putting a clamp on the hose.

Report back.....

Reply to
Teddy Bear

Mike,

Thanks for replying, though based on the later replies to your question, I'm not surprised at the results.

Good luck with the repair!

Bill

Reply to
Bill Schwab

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