Q. My air conditioner and heater on my 1997 Mustang will only blow out the defroster vents. It gets vacuum, but will not blow out other vents. Where are the vacuum lines for the front vents?

A. Vacuum lines can be as complicated as wiring diagrams in today’s cars. Most cars for safety purposes will default to the defroster setting. There is a vacuum reservoir tank and vacuum motor. I would first check the vacuum tank and then the vacuum motors which are attached to the duct system. It is also possible one of the arms that go from the vacuum motor to the ducts doors is broken.

Q. I have a 2001 Ford Windstar with 184,000 miles on it. Recently, I started to hear a ticking noise and was advised by a mechanic to use Slick 50 additive and heavier grade oil. The van still runs good and the noise only appears from time to time. What do you recommend?

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A. A ticking noise is typical of a valve lifter problem. The additive and heavier oil may have helped somewhat, although I have seen better results with an additive to help clean the valve system. You might want to try something such as Marvel Mystery Oil; this will help clean the valve system. Once the engine is quiet then change the oil again and hope for the best. If the noise is related to a worn bearing then additive won’t really help and eventually the engine will fail. Depending on how you drive and if you take it easy the engine could last a long time.

Q. I have a 1999 Caddy with only 36,000 miles on its Northstar engine. The car overheats after about 50 miles of highway driving. I have been told it could be a head-gasket or a blocked radiator. Could there be a problem with the cooling fan? The cooling system does not show any leaks and there is no white smoke out the tailpipe, what do you suggest?

A. Both of these possible problems are fairly easy to diagnose. A technician with a gas analyzer or an engine block leak check kit can easily verify a possible head-gasket problem. A blocked cooling system can also be easily verified. A faulty cooling fan will also cause fairly quick overheating, although this is typical of around town driving.

Q. My 2007 Suzuki with 175,000 miles on it has a slight shimmy between 50-70 miles per hour. I took it to the shop and they checked all the front end parts and everything was okay. I had the shop balance and rotate tires, but the problem is still there. Any ideas what might be causing this?

A. Vibration at speeds over 50 miles per hour can usually be attributed to tire vibration. I would ask the shop to carefully check the tires and wheels for “out-of-round”. The tires should also be checked when they are installed on the car. Also, if there is rust on the wheels or hubs the tires will not run true and will vibrate.

Q. How do you completely clean fuel system after bleach has been poured into gas tank?

A. I’m guessing bleach was added by a vandal and not because you wanted to clean the fuel system. Don’t drive the car. At a minimum you will need to remove the gas tank and completely flush the tank and fuel line and perhaps replace the fuel pump. The chlorine in the bleach is very corrosive to the fuel tank, lines and even the engine. Depending on coverage, this repair may be covered by your car insurance.

Q. I have a 2006 Lexus 250 IS, which runs great and has close to 80,000 miles on it. It’s not due for another major maintenance service until 90,000 miles. In between major services I go to local places for oil changes, tire rotations and other minor service. The interim service list includes one item, “axle shaft flange bolt re-torque”. I’m not familiar with this service and I am concerned it is not addressed by either of these interim service providers. What is this re-torque, and should I also be taking my car to a trusted local mechanic to do this every 5000 miles, as recommended by the Lexus’s servicing schedule?

A. On the Lexus service schedule there is a listing to check/re-torque (check tightness) of the driveshaft flange bolts. Any shop should be able to check and tighten these bolts.