OK guys, sorry about the non-Vette question, but I've never seen or heard of this and I'm guessing someone out there in C3VR-land has.  Problem just recently started with my '95 Chevy Tahoe.  Sometimes when I have just started it up from cold, the first time I touch the brake pedal, the power brakes kick-in big time and I come to a SCREECHING halt.  After maybe 1 - 2 minutes and pressing the brake pedal a couple of times, everything is OK.  Any ideal what is going on?

Thanks! 

This often happens with brake contamination.  Dirt, water, brake fluid, axle fluid etc on the lining all can cause this.  Water is a common one.  In very wet weather the rotors/drums and semimetallic linings rust a bit.  After a few stops it cleans the fine rust off, and they are okay again.  If the brakes have been recently replaced it can be a compatibality issue between the type of lining and the metal of the rotor/drum.  Inexpensive aftermarket rotors and drums are bad for this.  Aftermarket linings are also noted as a wet weather cause for rust.  This varies a lot on brands. 

Years ago GM had a problem with moisture getting into the power brake booster and creating a similar problem.  That is why our cars often have the filter in line to the booster vacuum supply.  That should not be a problem on your Tahoe.

About a month ago my Celebrity started doing this same thing very badly.  I cleaned the rear drums and linings, and lightly sanded all friction surfaces.  Problem cured.  The first time the Celebrity it did it about a year ago, the wheel cylinders were seeping brake fluid onto the linings.  That time was all new cylinders, lines, linings, drums, and hardware.  They were just worn out.

Thanks Ken.  In fact, it was a damp, rainy day here yesterday.  I'll have to note the weather conditions whenever it happens again in the future (hopefully never, but that's obviously wishful thinkin'.)

However, it doesn't feel like the pads are grabbing to me.  It feels more like the instant I first touch the pedal, the booster is somehow going into "overdrive" and locking up the brakes.  Is that the symtom of the booster problem you described?

Thanks!

It's possible the valve in the booster is overreacting.  In reality, when you have power brakes, you are not applying the  brakes.  You are operating a valve that controls the booster, which in turn applies the brakes.  There is a reaction disc or rod to give the feel of pressure on the pedal.  This also allows you to operate the brakes when there is not vacuum.

Having a valve overreact is fairly rare.  But I have seen it happen.  Usually it fails to apply, and the brakes are very difficult to push.  Pay close attention to the pedal feel when it does this.  If the pedal has normal resistance, then seem to go down much easier when the brakes are acting grabby, you could have a valve overreacting. And yes, moisture could affect it.