Q: My car runs hot, then cools down, and then heats up again

Hello. Your attention should be turned toward the fact you are going through a lot of coolant. If you can not visibly see a leak spraying or any evidence of a leak on the ground, then your engine is consuming the coolant. You should check your oil and see if there is any milky looking fluid or residue there. This is going to tell you whether coolant is mixing in with your oil, and the cause in this case would likely be a failed head gasket. These are easy to replace, but very hard to access, making for a tricky repair. Not that we recommend inhaling exhaust fumes, but if you smell a sweet odor coming from the vehicle, that too is a sign you are burning coolant. A cracked head will also cause this symptom. Further testing and an inspection by a certified technician, such as one from YourMechanic, is needed to properly diagnose your coolant level problem.