Brake Bleeding with All-Wheel ABS (2000 Z-71 OBS Tahoe)

[Wardi]

Hey All! Do I really need a Tech 2 scanner to bleed the brakes correctly on an "all 4 wheel" ABS brake system on a 2000 Z-71 OBS Tahoe? I see some differing opinions here and elsewhere. Seems getting a Tech 2 scanner could get kinda pricey. Seems some say if you just brake real hard a couple times after the initial bleed, air will "cycle through" system and then you just need to re-bleed. Attached is a pic of my brake system -both just FYI and to see if I could up-load a pic! Been a while since I've been on here, but the Truck is still awesome!

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[delta_p]

My answer is....no.

You really only need to activate the ABS if you broke into the ABS system. Like replacing the combination valve, or the Brake Pressure Modulator Valve (the thing under the black cover in your photo with Kelsy-hayes on it). The lines go from the master cylinder, to the combination valve bolted to the BPMV, through the BPMV and then to wheels.

In normal mode, there are valves in the BPMV that are blocking the ABS pump and accumulators from the normal path which provides a route to the wheels straight through from the master cylinder, to the combination valve, through the BPMV, and to the two front wheels and to the rear wheels. All you are doing when using the scanner, is cycling the valves, and running the pump, in the BPMV which does eject fluid and any air into the normal route which you can bleed away. But if you haven't broken open the BPMV it shouldn't have air in it, only old fluid in the accumulators.

When I replace master cylinder, wheels cylinders, etc. I usually don't use the scanner. But occasionally when I replace the brake fluid, I use the scanner to get all the fluid.

You can activate the valves and pump by braking hard on gravel too. but the scanner is much more convinient.