Q Is there any magic to doing a brake job -- pads and rotors all around -- on a 1998 Oldsmobile Aurora? The parts at the auto parts store are about $280 with tax. The brake shop wants $1,000 or so. I figure I'll save some on this one.
A The only magic is a willingness to try, the right tools and the patience to make sure the job is done correctly. I reviewed pad and rotor replacement in Alldata, and the only potential trap is if you find it necessary to bleed the brakes.
With the Teves Mark IV ABS and traction control systems on this vehicle, you might have to use a special "auto bleed" procedure if you suspect air is trapped in the secondary circuits in the brake pressure modulator. If no air is trapped in these circuits, which are normally closed during non-ABS/traction control operation and bleeding, you can bleed the brakes in a routine fashion.
Replacing the pads and rotors involves raising the vehicle safely on jack stands, removing the wheels, siphoning most of the brake fluid from the master cylinder reservoir to prevent overfilling, unbolting and removing the caliper (here's where you might need a special socket), compressing the caliper piston back into the caliper with a large C-clamp, then removing the old pads and retainers and installing the new set.
Before remounting the freshly loaded caliper, slide the old rotor off the wheel studs and hub, clean any rust off the surface of the hub and slide the new rotor in place. Remount the caliper, top up the master cylinder reservoir, apply the brakes several times to move the new pads into contact with the new rotors, recheck the fluid level ... and you're basically all set.
If you have a dial indicator or some type of run-out gauge, check the new rotor for run-out, or "wobble." You can use the wheel nuts to secure the rotor to the hub, rotate it by hand and check to make sure there's no more than 0.002 inch of run-out. If there's more than that, you can try reinstalling the rotor in a different orientation.
If the new rotor still has excess run-out, it will require the special equipment at a professional shop to "true" the rotor. But you can use your electric drill with a light sanding disk to scuff the new rotor surfaces to aid in bedding the new pads -- this will help ensure quiet brakes down the road.
Q I have a '96 Chrysler Town and Country with a 3.8-liter V6. It will not start. I am getting no spark and no fuel. The fuel pump is running, and I have pressure in the line, but the injectors are not firing. As far as I can tell this vehicle does not have an ignition control module, so the only thing I can think of is that the PCM is shot.
A While it might be a PCM problem, it's more likely an issue with something that influences PCM operation. Start by checking the ASD (auto shutdown relay) in the power distribution panel behind the battery. This relay supplies voltage to the injectors, ignition coil and oxygen sensors. If it has failed, the engine won't have ignition or injector function.
Next, check for output signals from the cam and crankshaft position sensors. Any loss of signal from either of these two key PCM inputs will prevent the PCM from "knowing" the engine is cranking.
Q I have a diesel semi that has several batteries. The truck has room for four batteries but has only three installed. Someone gave me an almost-new battery that I would like to add for winter. Do they all have to be the same size, or can they be different?
A Well, 12 volts is 12 volts, regardless of battery physical size. The issue is how the four batteries are employed in your tractor-trailer. If they are all connected in parallel, then adding a fourth battery would increase the total amperage capacity of the battery system. As long as you can securely mount the new battery so it doesn't bounce around, I don't see any problem with installing it.
Again, the key is how the batteries are employed. If they are paired in series to provide 24 volts instead of 12 volts, they should be matched pairs for equal charging and full service life. If they are wired separately to power different systems on the truck, or they're connected in parallel as described above, the extra battery should work just fine.
I received a helpful e-mail from Kevin Bohrer: