Troubleshooting Troubleshooting – Cooling System – 2.5L NA Estimated reading: 2 minutes Contributors Overview This troubleshooting guide is designed to help identify and resolve cooling system issues specific to the Porsche 944 3.0L S2 (1989–1991). Proper cooling is critical for maintaining engine performance and preventing damage due to overheating or coolant loss. This procedure focuses on common cooling system problems, such as overheating, overcooling, coolant loss, and improper cooling fan operation, tailored for the 3.0L S2 variant with its late-model alloy control arms and specific cooling system components. Overheating Possible Causes Checks Procedure Improper coolant level Check coolant level and fill if necessary. N/A Cooling fans, thermofan switch, or fan relay not operating correctly Check cooling fan operation using COOL-01. COOL-01 Air in cooling system Fill and vent cooling system using COOL-02. COOL-02 Head gasket A leaking head gasket can allow cylinder gases to pressurize the cooling system, causing overheating. Perform a compression test or cylinder leakdown test, or have a radiator shop test coolant for exhaust gases. N/A Faulty thermostat Remove and test the thermostat using COOL-08. COOL-08 Wrong thermostat Ensure the correct thermostat and sealing ring for the 3.0L S2 water pump are used, as described in COOL-07. COOL-07 Bad water pump Check for pulley slippage by marking the water pump shaft and pulley, then observing alignment during engine operation. If slipping, tack weld the shaft to the pulley on opposing sides for balance. N/A Faulty coolant reservoir cap Check if the cap holds the correct pressure (in millibars, convert to PSI if needed). Test at a radiator shop if necessary. N/A Radiator issues Remove radiator using COOL-04 and have it tested/cleaned at a radiator shop. COOL-04 Overcooling Possible Causes Checks Procedure Faulty thermostat Remove and test the thermostat using COOL-08. COOL-08 Loss of Coolant Possible Causes Checks Procedure External leak Use a coolant pressure tester to pressurize the system while cold to locate leaks at coolant hoses, water pump, or heater control valve. N/A Internal leak Check for head gasket or oil cooler seal leaks by inspecting for white exhaust smoke, wet spark plugs smelling of coolant, or oil in coolant. Perform a compression or leakdown test. N/A Improper Cooling Fan Operation Possible Causes Checks Procedure Cooling fans Check cooling fan operation using COOL-01. COOL-01 Sources Clark’s Garage Pelican Parts Porsche 944 Workshop Manuals YouTube Tagged:Cooling System Troubleshooting Troubleshooting – Cooling System – 2.5L NA - PreviousTroubleshooting – Clutch – 2.5L NANext - Troubleshooting – Cooling System – 2.5L NATroubleshooting – Heating, Ventilation, and Air Conditioning (HVAC) – 2.5L NA
