Expert: Brad Sears - 5/22/2008

Question
I have a 1953 Buick Special that I drove recently, parked it in the garage, and then the next day noticed that the top radiator hose had collapsed.  I'm thinking it may be one of several reasons why this happened - bad hose, bad radiator cap, low level of antifreeze, etc.  I'm inclined to start by replacing both radiator hoses and the radiator cap to see if that fixes it (the cap does look a bit worn).  Do you think that's a good first step?  What else do you think I should do?  Thanks so much for your time.


Answer
Radiator caps are pressure/vacuum caps. When the engine heats and the coolant expands it will allow pressure to build to the specified level and then vent holding the pressure steady. When the engine cools the coolant shrinks and causes a vacuum that is supposed to be bred off by the vacuum portion of the cap. When it does not allow air back in or fluid in from the overflow tank then the upper hose will collapse. The reason that the lower hose does not collapse is that there is a spring inside the hose to keep it in shape at high engine speeds as the water pump creates a low pressure that makes the coolant flow.
Brad