By now, it's obvious to most service shops that cooling system service is an absolute "must-do" on any nameplate. Once a cooling system suffers long-term neglect, it turns into an ongoing source of problems for the owner and his service technician because, when corrosion starts to take place, the effects can't be reversed. For that single reason, it's especially important to sell your customers the "Complete Cooling System Service."

Last month, we addressed some radiator clogging issues (see "Ending Coolant Flow Restrictions," July Underhood Service). This month, we look at all of the remaining components of the vehicle's cooling system.

The first step to a cooling system check is to look for corrosive influences. Remember, ethylene glycol-based coolants incorporate a considerable additive package that's designed to control the extremely corrosive tendencies of the coolant itself. The additive package not only prevents corrosion, it also prevents electrolysis, which is the tendency of different metals to dissolve and migrate throughout the coolant. This migration is caused by a mild electric current flow that is caused by dissimilar metals being suspended in a water-based liquid. Thus, when the additive package is depleted, critical gasket sealing surfaces become eroded and coolant passage tubes in the radiator become clogged. In addition, sediment caused by rust from iron cylinder blocks settles to the bottom of the...