recently bought a 1989 hiace an im worried if it is overheating. Check coolant level and it is perfect, but when the radiator cap is opened it is dry inside. Very little driving experience. Is this normal? Also temp gauge is broken on van Thanks
Under the radiator cap should be full - no air. Fill up the radiator and make sure your overflow bottle is filled to the full mark. Check it frequently and look for leaks until you can be sure it is not leaking. It may take a couple heat cycles to get it full, as there are places coolant goes when the engine is hot that you cannot fill (or at least have a hard time filling) when the engine is cold. I will fill the radiator, put the cap on, start the engine, pull the cap off, and top if off. NEVER REMOVE THE CAP WHILE THE ENGINE IS HOT. The coolant is under pressure. If you remove the cap while the engine is hot, very hot coolant will spray everywhere and can burn you.
The overflow bottle serves 2 purposes. The first is to provide space for thermal expansion of the coolant. This allows it to overflow into the bottle when the cap pressure is exceeded, and draw from the bottle once it has cooled down and the pressure has dropped. The second purpose is to provide a 1 way check valve to assist in bleeding air from the coolant system. Air can escape, but it pulls coolant back in.
You mention the temperature gauge not working. The sender for the gauge works by being partially submerged in coolant. With no coolant, it will read cold.