91 s10 
I think I have a couple issues.  one its leaking coolant on the bottom right corner.  however, it doesen't do it all the time.  second, when it dosen't leak I fill it up with water but it still over heats.  it over heated the other day and I went to add water.  took the cap off and the pressure was crazy.  water went about flying everywhere.  that mean the water pump is not working?  thanks.