Troubleshooting Troubleshooting – Cooling System Estimated reading: 3 minutes Contributors Overview This troubleshooting guide is designed to help diagnose and resolve cooling system issues specific to the 16v engine Porsche 944 S / S2 (1989–1991). The cooling system is critical for maintaining optimal engine performance and preventing damage due to overheating or coolant loss. This procedure addresses common symptoms such as overheating, overcooling, coolant loss, and improper cooling fan operation, tailored for the S / S2’s 16v engine and late-model alloy control arm configuration. Pink and blue text represents links to additional resources, tools, parts, and partner websites. Engine Overheats 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, 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 on the water pump shaft. Remove the top timing cover, mark the shaft and pulley with a paint pen, and verify alignment after starting the engine. 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 pressure stamped on it (typically in millibars). Test at a radiator shop if a pressure tester is unavailable. N/A Radiator issues Remove radiator using COOL-04 and have a professional radiator shop test and clean for blocked passages or external debris. COOL-04 Engine Overcools Possible Causes Checks Procedure Faulty thermostat Remove and test the thermostat using COOL-08. COOL-08 Engine Loses Coolant Possible Causes Checks Procedure External leak Pressurize the cooling system while cold using a coolant pressure tester to locate leaks. Check coolant hoses (radiator, heater control valve, return from heater core), and water pump (may require removing upper timing cover). N/A Internal leak Check for head gasket leaks (white smoke from exhaust, wet spark plug smelling of coolant, compression/leakdown test), oil cooler seal leaks (oil in coolant), or rare cracked cylinder walls. N/A Cooling Fans Do Not Operate Correctly Possible Causes Checks Procedure Cooling fans Check cooling fan operation and troubleshoot using COOL-01. COOL-01 Sources Clark’s Garage Pelican Parts Porsche 944 Workshop Manuals YouTube Tagged:Cooling SystemCooling System Troubleshooting Troubleshooting – Cooling System - PreviousTroubleshooting – ClutchNext - Troubleshooting – Cooling SystemTroubleshooting – Engine
