Watch for leaks or stains under the car. If there is a persistent oil leak that you are sure is coming from your car, determine if it is coming from your transmission or possibly from your power steering system. Fluid coming from either place is an indication of a hydraulic valve failure.

Check your car for proper transmission fluid color.

Check your car's transmission fluid for the proper color by pulling the transmission dipstick out of the transmission. Transmission fluid is a transparent red oil, and should not be cloudy or muddy. If the fluid is cloudy or muddy, or it has a burned odor, it may be an indication of a valve failure.

Unusual noises when shifting are indicators of hydraulic valve failures.

Listen and feel for new noises, vibrations and shift behavior when you are driving. If shift points are erratic or you hear noises when shifting, you should have your car checked immediately. Unusual noises, vibrations and shift behaviors are indications of hydraulic valve failures.

Metal erosion is one of the chief identifiers of hydraulic valve failure.

Check the car engine for metal erosion. Metal erosion is a chief side-effect of cavitation, which occurs when the hydraulic fluid supplied to a particular hydraulic circuit falls short of the amount it actually requires. Cavitation often causes hydraulic valve failure.