Source: Snap-on

Few people welcome that first bead of sweat that runs down your back while driving home from work during summertime. Likewise, your car's engine likes to keep cool as well. Snap-on Tools Company offers these tips for keeping both yourself and your vehicle cool during the hottest summer months.

Yourself (A/C System)

Locate your A/C compressor (see manual) and trace the entire path of the two hoses leading out if it. Look for two things:
Any cracks of decay in the hoses or tubes.
Oily substances near the joints where hoses meet parts. Even the smallest leak at a joint can shut down your entire A/C system.
If the inside of your vehicle is not as cool as it has been in the past, it may mean a switch in the system has shut down the A/C -- a safety precaution engaged when your refrigerant level is too low. If this happens, have your local service technician test it.

When you're not getting much air flow out of your vents with the A/C on, it does not necessarily mean you have a problem with the A/C. It may be the result of a blown fuse, which is an indicator of a problem elsewhere in the car.

Your Car (Coolant System)

Check your engine coolant fluid level and make sure it's full. Over time, it's natural for coolant to become contaminated, so have your system flushed and replenished about every three years or 36,000 miles -- or as recommended by the manufacturer.
Overheating is often the result of poor air flow through your radiator. When your car is cool, check under the cap of your radiator for crystalized residue formed around the top or on the cap. It's a sign of restricted air flow and may lead to overheating, so have a technician replace or "flush out" your radiator.

Your car is just as likely to overheat during stop-and-go traffic as it is during highway travel, so keep an eye on your temperature gauge (or engine light). If you gradually notice an increase reading, immediately check your coolant level; then take your car to the nearest service shop for testing.