A/C, Thermostat, Hose, & Coolant Information
AIR CONDITIONING CONDENSER
With the engine off, check for distortion of the condenser cooling fins on both sides of the condenser. To check the side closest to the radiator, remove the upper fan shroud, and tilt the radiator towards the rear of the vehicle. When performing this procedure, check for air flow restrictions within the condenser cooling fins. Like the radiator fins, the condenser fins can also become plugged by debris. This not only affects the air flow going to the radiator, but also reduces the performance of the air conditioning system. If possible, clean both the radiator and condenser cooling fins with pressurized tap water (garden hose).
AIR CONDITIONING SYSTEM
Check that the air conditioning system is not overcharged. An overcharged system will cause excessively high system pressures. These higher pressures relate to higher temperatures in the condenser. As a result, the air flow moving across the condenser to the radiator is warmer than normal. This warmer condition reduces the ability of the radiator to dissipate its own heat.
THERMOSTAT
Check that the thermostat is operating correctly. The thermostat should open when the engine reaches approximately 195 degrees F. To verify this, connect a scan tool to the vehicle's ALDL Connector and monitor coolant temperature. The coolant temperature should be below 140 degrees F before the start of this test. Start the engine, let idle and observe the coolant temperature. The temperature should rise at a steady rate until the thermostat opens (about 195 degrees F). At this point the coolant temperature may momentarily drop a few degrees, or stay constant for a minute or two. If the thermostat opens at a temperature lower than 190 degrees F or higher than 200 degrees F, it should be replaced.
HOSES
Check that the upper and lower radiator hoses as well as all heater hoses are not collapsed or kinked. Such restrictions can interrupt or reduce the flow of coolant.
COOLANT
Today's vehicles are designed to operate with a 44/56 solution of antifreeze and water for optimum cooling system performance. This gives freeze protection to -20 degrees F. In colder climates a 50/50 solution is recommended for freeze protection to -34 degrees F.
These solutions give the correct cooling system balance of freeze protection, heat dissipation and corrosion protection.
When cooling systems are drained for any reason it is important that the correct concentration of antifreeze be maintained. Increasing or decreasing the antifreeze concentration from the desired mix can have undesirable effects on the system.
Listed here are some useful facts concerning antifreeze concentrations:
^ GM coolant specification 6038-M (P/N 1052103) is recommended for all light and medium duty trucks with gasoline or diesel engines.
^ A 50/50 antifreeze mix increases cooling capacity about 15% over clear water.
^ Maximum freeze protection is obtained at about 69% antifreeze. Higher concentrations actually raise the freeze point.
^ The freeze point of 100% antifreeze is about -8 degrees F.
^ Engine damage from freezing due to very high concentrations of antifreeze is not likely for two reasons.
1. High concentration solutions do not freeze to a solid, but become a heavy slush.
2. High concentrations of antifreeze contract rather than expand at their freezing point.
COOLANT LEVEL
Check the overflow reservoir to see that the radiator and cooling system are filled to the proper level. If the reservoir level is low or is completely empty, check it for leaks.