Savvy, special tool needed to fix rearview mirror
Dear Mike: My rearview mirror fell off the glass of my windshield. It doesn’t have a setscrew to tighten the base plate into place — instead it looks like it has some sort of spring mechanism.
I need to get the base plate off so that I can reglue it to the glass.
— M.P., via e-mail
A: The use of a spring clip is a production shortcut — it allows the line workers to simply clip the mirror on without using any tools. This means that you and I do need a special tool, or at least some savvy. KD Tools, at www.kd-tools.com, offers a special tool for Ford rearview mirrors. There are other special tools for other vehicles available from KD and from other manufacturers as well.
I’ve always managed to remove these things with nothing more than a small screwdriver or a short piece of welding rod and an assortment of blue language. You need to depress a small tab in the mirror base and then clear the button from its rails.
Dear Mike: When I go up a hill or accelerate smartly in my Dodge Dakota, there’s a thumping noise when the doors inside the heating/defrosting system bang shut. All the air goes to the defroster and none to the heater or air conditioner.
As soon as I reach the top of the hill and relax on the gas pedal, there’s another thump and all is back to normal.
I’ve checked all the vacuum lines and put a new check valve in the line, but nothing has helped.
— E.E., via e-mail
A: You’re correct to start looking for a vacuum problem. Blend-air doors in the HVAC system are controlled by small, vacuum-powered motors. Release their vacuum supply and they return to their relaxed state against spring pressure. The check valve is supposed to maintain a vacuum in the system when the intake manifold drops under heavy throttle application.
You’ve got a small vacuum leak in the system, on the HVAC-control side of the check valve. It’s big enough to let the system slam doors shut when you punch the throttle, but small enough that the continuous supply of vacuum under high-vacuum conditions, such as idle and cruise, allows the mechanism to work normally.
Get back under the dash and hunt for the hiss of the leaking hose or fitting. A 3-foot piece of heater or garden hose makes a good stethoscope. A hand-held vacuum pump may also be useful, because the engine may make enough noise to mask a faint hissing.
Check all the rubber fittings that connect hoses to hard parts. The rubber tends to dry out and leak, even though it may still look fine.
Dear Mike: My 1987 Chrysler New Yorker takes on speed by itself, without my touching the gas. If I touch the brake pedal, though, it’s normal. It’s scary.
— S.R., no address given
A: Your car is old enough to have deposits inside the throttle body that can hold the throttle blade slightly open. Or maybe the accelerator cable or pedal are slightly sticky. Clean and lubricate these items. The procedure for cleaning the throttle body isn’t trivial — either get a mechanic to do it or look it up at www.popularmechanics.com under “Car Care.”
On the other hand, from your brief letter I’m not sure if you have a sticky throttle or a true case of unintended acceleration. If the vehicle is actually self-accelerating, a mechanic with a scan tool and a good head on his shoulders needs to check your cruise control and idle-speed controller for proper function.
The idle-speed controller can admit only a small amount of air into the engine if it is completely open, but that may be enough to maintain speeds of 25 mph to 30 mph. It may be dirty, or a malfunction of some other sensor may be causing it to open at the wrong time. Ditto the cruise control.
A longer shot might be a manifold vacuum leak.