, Salem, MA

September 7, 2013

Auto Scanner: Mustang’s power brakes are slow

Auto Scanner
Larry Rubenstein

---- — Q: I have a 1996 Ford Mustang that I just purchased with a six-cylinder engine and 106,000 miles. The problem is that the brakes are not functioning well. They are supposed to be power, but when I try to stop, the pedal is hard, but it will not stop right away. It slows down but will not panic stop. I’m afraid to drive it over 25 mph. Almost as if rotors are greased. It has been sitting for a while. Is there something I can do to fix this? The car is in excellent condition, plus it is a convertible.

A: From the way you describe the problem, I would be looking at the power booster for the power brake system. One way to check for power booster operation would be to turn off your car, pump your brake pedal about a half-dozen times. Next, with your foot on the brake, start the engine. When the engine starts, the brake pedal should drop down at least 25 percent. If that happens, then your power booster is working; if it does not, then the vacuum source and check valve need to be checked, as well as a torn membrane inside of the booster. If all checks out well there, then the caliper and caliper slides need to be checked. Beyond that, the wheel cylinders at the back wheels may also have to be checked for frozen pins. It’s a pretty simple system on your Mustang and shouldn’t take more than an hour to diagnose.

Q: There is a problem with the air conditioner in my 1998 Mazda 626, which has a four-liter, four-cylinder engine, five-speed manual transmission and 204,000 miles. This summer, especially during the heat waves, the air conditioner provided and continues to provide cold air for 10 to 20 minutes of driving (depending on how hot the day). During that time, the air-conditioning relay can be heard to cycle in the usual manner, and air-conditioning system load can be felt coming in and out of the engine. After 10 to 20 minutes, however, the air-conditioning system ceases to go on and off, and the air from the vents gradually loses its cool. I conclude that the system has reached the limits of the amount of its refrigerant. The air-conditioning system has never been serviced in the 204,000 miles we’ve put on the car since buying it new. Is the behavior described indicative of the need for a refrigerant recharge? If so, given that summer is ending, I’m willing to live with it and recharge next spring.

A: There may be moisture in the air-conditioning Freon. This will cause the expansion valve to freeze up and increase the high side pressure, which will end up turning off the air conditioner earlier and earlier until the pressure is so high the air-conditioning unit will not turn on again. That being the case, the expansion valve and the receiver drier should be replaced before the recharge of fresh R-134.

Car Care Tip: It is important that your air conditioner works year-round because it acts as a dehumidifier to defrost your windows quickly and safely.


Larry Rubenstein is a master technician who owns a North Shore service station. His column appears every Saturday. Write to Larry at The Salem News, c/o Auto Scanner, 32 Dunham Road, Beverly, MA 01915, or send an email to