1. Thermostat: This is the most common culprit. A stuck-open thermostat allows coolant to constantly circulate without reaching a high enough temperature.
* Check: The easiest way to check is to feel the upper radiator hose. If it's always cold or only slightly warm, the thermostat is likely stuck open. You can also carefully remove the thermostat (after the engine cools completely) and place it in a pan of hot water. It should open at the temperature specified by the manufacturer (usually around 195°F).
2. Coolant Level: Low coolant means less fluid to heat, leading to a cold engine.
* Check: Carefully inspect the coolant reservoir. Top it off if needed using the correct 50/50 mix of coolant and distilled water. Never open the radiator cap when the engine is hot.
3. Water Pump: A failing water pump may not circulate coolant efficiently.
* Check: With the engine running, carefully feel the upper and lower radiator hoses. There should be a noticeable difference in temperature – the upper hose should be significantly warmer than the lower. If both are cold or only slightly warm, or if you hear a whining noise from the pump, it could be faulty.
4. Radiator: A clogged radiator restricts coolant flow, preventing efficient heat transfer.
* Check: Inspect the radiator for any debris or blockages. A professional flush might be needed if it's clogged.
5. Head Gasket: In rare cases, a blown head gasket can cause coolant to leak into the oil or exhaust, reducing the amount of coolant circulating through the engine. This would typically be accompanied by other symptoms such as white smoke from the exhaust, milky oil, or loss of coolant without any visible leaks.
* Check: Look for signs of a blown head gasket (see above). This is a more involved issue requiring professional diagnosis.
6. Cooling Fan: A constantly running cooling fan can force cold air over the radiator, preventing the engine from reaching operating temperature, especially if it's only slightly warm outside.
* Check: Observe if the cooling fan is running excessively or when it shouldn't be. There might be an issue with the fan's sensor or control module.
7. Air Pockets in the Cooling System: Air trapped in the cooling system can impede coolant flow.
* Check/Fix: This is often solved by bleeding the cooling system. Look up the procedure specific to your 1994 Chevy Suburban in a repair manual or online. This often involves opening bleed valves at high points in the cooling system to release trapped air.
Recommendation: Start by checking the thermostat and coolant level. If the problem persists, it's best to have a qualified mechanic diagnose the issue to prevent further damage. Ignoring a consistently cold running engine can lead to significant problems down the road.
