My Subaru overheats even with coolants
I drive a Subaru Legacy B4 which overheats badly. I have taken it to a radiator specialist who even had the courtesy to give another radiator while as he was fixing mine.
The vehicle overheated almost immediately with his radiator in spite of putting some coolant. We tried changing the caps on both radiators but that yielded little.
We also realised that the water was sucked back from the reserve tank when the engine didn’t run for a while. What is the problem?
The fact that the coolant is being sucked back and forth from the reserve tank is a good sign that your radiator cap is working perfectly.
It is a two-way valve that should release water and steam from the radiator when it is too hot or boils over and allows water from the reserve tank to replace the vacuum created in the radiator when it cools off.
I suggest that you have your water circulation pump checked. If your fans are working, I suggest that you have other areas of the cooling system checked for leaks.
If there are no leaks and the pump is working properly, the thermostat is failing to open for the coolant to circulate through the radiator. Get these items checked as they are the most probable cause of overheating.