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Thursday, July 23, 2009

issue with the brakes. The pedal is soft and tends to go to the floor

I am in Australia and we have a 97 Chevy Silverado that has been converted to right hand drive. We have an issue with the brakes. The pedal is soft and tends to go to the floor. We have changed master cylinders, pads, discs etc. etc. and now have bypassed the ABS and find that they work much better, but still a soft pedal. Our mechanic is wondering if there is a specific way of bleeding the ABS as this is where there seems to be some air that cannot be gotten rid of. Normal procedures are not working (normal in Aus anyway...) It is not an uncommon problem I believe in converted vehicles, but aside from being unsafe, our truck is now unsaleable until the ABS is reconnected and the pedal is firmer. Any suggestions would be appreciated. Already Tried: Bleeding brakes new master cylinder new discs new pads bypassing ABS
The ABS system on this vehicle has always been problematic. There are a couple of things that will help when you bleed this system. This is a two person procedure and may require a pint or more of brake fluid per wheel. The old fashioned manual method with modification is best here, starting at the right rear wheel use a clear tube on the bleeder in a small glass of brake fluid crack the bleeder, have the person in the cap depress the brake pedal halfway never more and hold, the other person closes the bleeder and you both wait 15 - 20 seconds then the pedal is raised, the bleeder is cracked and the pedal is pressed, bleeder closed, pedal held halfway down etc. until all air stops coming out of that corner. Continue around to all the wheels in the same manner. Once you have run a gallon of fluid through use a Tech2 scanner or a scanner that allows you to operated the automated bleed procedure in the ABS computer. After doing the automated bleed procedure once go back and re bleed the wheels manually. There are accumulator pistons in the ABS hydraulic unit that may be leaking, pull the small rubber cap from the two at the bottom of the unit and slide a small screwdriver in the hole until it bottoms on the piston and have a helper step on the brake pedal if the screwdriver is pushed out the piston is moving and the hydraulic unit is junk and must be replaced. These systems are soft low pedals when they are working properly and have been the bane of many a mechanic over the years I will be glad to see the last of them in the junkyard.

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