Possible Causes:
* Radiator: A clogged radiator or a damaged radiator core can significantly restrict coolant flow, leading to overheating, especially in hot weather. Inspect the radiator carefully for debris or damage. You can try flushing it again with a radiator cleaner, but a replacement might be necessary.
* Radiator Fan: The radiator fan might not be turning on when needed, or it might be malfunctioning. Check the fan's operation – does it turn on when the engine reaches a certain temperature? Verify the fan clutch (if applicable) and the fan motor itself. A faulty fan relay or a problem in the electrical wiring to the fan could also be at fault.
* Head Gasket: A blown or leaking head gasket is a serious possibility. This allows combustion gases to enter the cooling system, pressurizing it and causing overheating. Symptoms of a head gasket problem include:
* White smoke from the exhaust.
* Milky or foamy oil.
* Loss of coolant without visible leaks.
* Sweet-smelling exhaust (due to coolant leaking into the combustion chambers).
* Pressure build-up in the cooling system (radiator cap might pop off). A pressure test of the cooling system is a must here.
* Cooling System Leaks: Although you've checked for obvious leaks, there might be a small, hard-to-detect leak somewhere in the system – a tiny crack in a hose, a pinhole leak in the radiator, or a leak around the water pump gasket. A thorough visual inspection with a pressure-tested cooling system is essential. Dye in the coolant can help locate leaks.
* Low Coolant Capacity: Ensure the cooling system is properly filled and the coolant level remains stable. A small leak that only appears under pressure might not be easily detectable when cold.
* Timing Chain/Belt: A stretched or broken timing chain or belt (depending on the year and engine) can cause severe engine overheating.
Troubleshooting Steps:
1. Pressure Test the Cooling System: This is crucial to rule out leaks and head gasket issues. A mechanic can perform this test quickly.
2. Inspect the Radiator Carefully: Look for clogs, damage, or leaks.
3. Test the Radiator Fan: Verify that the fan turns on when the engine reaches its operating temperature. Check the fan relay and wiring.
4. Check for Leaks: Carefully inspect all hoses, clamps, connections, and the radiator itself for any signs of leaks. Look for dampness, discoloration, or coolant residue.
5. Exhaust Gas Test: A test that checks for exhaust gases in the coolant can definitively determine if the head gasket is leaking.
6. Check Coolant Level: Make absolutely sure the coolant is at the correct level, both hot and cold.
Recommendation:
Given that you've already tried the most basic fixes, it's highly recommended to take your S10 Blazer to a qualified mechanic. They have the tools and expertise to properly diagnose the overheating problem, especially if a head gasket or more complex cooling system issue is suspected. Ignoring overheating can lead to serious engine damage. The pressure test and exhaust gas test are key diagnostic steps that need to be done.
