Q: How to perform an operating check of the power brake booster system on 1997 through 2001 Toyota Avalon?
A: At first, press the brake pedal repeatedly a few times when the engine is off to test the power brake booster system. In case that it remains the same in terms of pedal reserve distance, it means that everything is functioning properly. And then lower the pedal when the engine is running and if it moves down insignificantly so this means normal operation. To check for air leak by starting and switching off the engine after one or two minutes. Therefore, if this happens each time one depresses the brake pedal, with each cycle being shorter than before, then there is an evidence of seal on the booster. Still while running car engine press brake pedal and hold down even as you switch off ignition. The booster is airtight if no change in pedal reserve travel occurs after being held for 30 seconds. Remember that power brake boosters should not be dismantled during removal but have to be replaced with new or rebuilt ones depending on their condition and availability of these units together with special tools necessary for disassembling them. Consequently take out rear brakes master cylinder, charcoal canister and air cleaner assemblies after removing charcoal canister and air cleaner assemblies from throttle body upper cover as shown in procedure titled air cleaner assembly replacement. Take away steering column cover pad located inside vehicle and find clevis connecting booster push rod to brake pedal; remove clevis pin retaining clip next pin. Lastly detach four nuts and washers securing power brake booster to firewall then pull it out. Once you have done this, do everything in reverse order tightening booster mounting nuts as well as clevis locknut firmly. Also check pushrod clearance specified for new power brake booster unit while measuring dimensions A-B-C to adjust pushrod length accordingly. After installing master cylinder braided hoses together with fittings adjust height of brake pedals also free play of them before bleeding system.