If you notice coolant near the radiator or the radiator cap, then you clearly have leaky coolant. Replacing the cap or checking for other cooling issues can help stop the leak and prevent engine overheating. Many symptoms of a faulty radiator cap can also be signs of another problem, such as the much dreaded head gasket failure
10 Bad Radiator Cap Symptoms In a Vehicle - How to Diagnose It - Motor Vehicle HQ
If you suspect you have an issue with your head gasket (s), it’s not a bad idea to replace the radiator cap first since it’s so quick, cheap, and easy, before throwing more time and money at a potentially expensive problem.
You can tell your radiator cap is bad if you notice coolant leaks or dried residue around the cap or radiator neck, a cracked or hardened rubber seal, or a rusty, unresponsive spring that fails to maintain system pressure
Also, watch for engine overheating or temperature spikes, bulging radiator hoses, and steam emissions These signs indicate the cap isn’t sealing properly, risking coolant. Replace the hose if you find cracks, signs of damage, or wear, even if the hose is not leaking. Coolant leaking from the radiator cap is often due to a faulty cap or high pressure in the cooling system
