That would not hurt much, but you may need to re-fill it and maybe bleed the system. When you fill it with coolant, start the engine cold and fill it. Turn the heater all the way to hot and wait until the temp reaches operating temperature and top it off again. If it looks really foamy, you may have to do it again. If the radiator cap is old, I would replace it since you did everything else. They can cause problems if they won't hold pressure.
Thursday, December 8th, 2011 AT 2:31 AM