Nissan Repair: over heating engine., courtesynissan, radiator cap

Question
QUESTION: my engine over heats after ten minuets in my 300z.  the cap leaks,  but is that enough to boil over the radiator? or should the thermostat or water pump be removed?  what else could cause this?

ANSWER: Cameron,

Yes, if the cap leaks off pressure it will allow the car to overheat.  Water boils at 212 degrees at sea level.  With a pressure cap the boiling point of the coolant increases and keeps the car from overheating.  I would first replace the cap and check the radiator and hoses to make sure all are good and tight and that the fan is working correctly.  If the waterpump leaks it would be bad.  I would also replace the thermostat if it has been a few years since it was replaced.  Buy a factory thermostat and radiator cap since they are the best.  courtesynissan.com or rockauto.com are good on-line resources if you have time and want to save a couple of bucks.

---------- FOLLOW-UP ----------

QUESTION: thank you for the information.  I still am having trouble though.   I replaced the radiator cap and thermostat.  the engine heats up to about 220 degrees when I shut it off.  what should I do?  I back washed the radiator out the drain plug , no sludge.  could the water pump cause this behavior?

Answer
Cameron,

The possiblity of a defective waterpump is remote since it usually will leak on the ground when the seals go.  The impeller usually does not come off the shaft.  I would have the system checked for exhaust gas in the coolant which would mean a leaky headgasket or an internal crack.  But, usually it is a leaky headgasket if there is exhaust gas in the coolant.  The parts store sells a do it youself kit for this for something like $30 bucks.  It will cost over $100 at a shop to have it checked unless you get a deal.