Magazine for the auto service professional
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59 | February 2016 The Tech Bench Tech tips From brake service to crank pulley bolts SUBARU BRAKE CLICK If you experience a one-time tap or click noise from under car after a cold start, the cause could be a metal brake line con- tacting the underbody. The ABS performs a self-test on start-up about 10 to 15 seconds after the engine start and speed sensor input is detected. The actuation of the internal ABS valving during the self- test sends a pulse of brake fuid pressure throughout the brake system. The tap or click noise may be caused by brake line contacting the underside of the foor when this pulse occurs. Insulating or slightly repositioning the brake line to gain added clearance will eliminate the noise. SQUEAKY SAAB If the owner of a 2005-2009 Saab 9-7X complains about a squeaking brake pedal, Saab says that the problem may be con- taminated brake fuid, which can swell the master cylinder's piston seals. Raise the hood and place an ear near the master cylinder while someone applies and releases the brake slowly. If you hear the squeak, fush and refll with fresh DOT 3 brake fuid. Then apply the brake a number of times slowly while listening for the squeak. If the squeak is still present, replace the master cylinder. FORD'S A DRAG If you experience a 2007 Ford Edge or Lincoln MKX with dragging brakes and premature pad wear, raise the car on a hoist with the engine running and the transmis- sion in park. Try to spin all four wheels. If all four wheels are dragging, the brake switch could be the culprit. Try removing the switch by turning it clockwise. If the brake pedal rises and the brakes suddenly release, replace the brake switch with an updated part number 8T4Z-13480-A. When installing the new switch, make sure that the brake pedal is in its normal rest posi- tion. The problem can be verifed with a scan tool and monitoring brake switch input while turning the wheels. The IVD light on the dash may be on due to pres- sure in the hydraulics with no actual switch output. If only the rear brakes are dragging, the problem lies with the parking brakes. With the brake pedal fully released, adjust the equalizer until both rear wheels turn freely. There should be no slack in the park- ing brake cable. Also, since the rear parking brake shoes are located inside the rotor hat, yank the rotor and check for debris that could be causing the pads to drag. MAKING LIFE EASIER If, for whatever reason, you need to remove and reinstall the crank pulley on a GM LS engine, you must replace the pulley bolt, as the original is torque to yield and should not be re-used. However, the OE bolt spec requires a tedious torque-plus-angle tightening procedure. Instead of dealing with this, use a new ARP crank bolt. The bolt is reusable and ARP specs a straight torque value with no angle tightening required. Granted, the spec is high (around 240 ft.-lbs.) but it will last and avoid the headache of tightening in tedious stages. ●