My wife's 99 Accord radiator needs water once a week. New radiator, radiator cap, upper hose and thermostat. We don't see any puddles on ground and it's not overheating till it get low. Suggestions?

 

Look for milky stuff on the oil cap/dip stick, also steam out the tailpipe.

 

Oil and radiator fluids are clean.

 

most likely a water pump going bad. there is a hole that coolant will come out of on the waterpump housing when pressure gets high and the pump isnt pushing the coolant through.

when my ol'e ladies cavalier snapped her drive belt, it shot half the coolant through those seep holes from the pressure build up.

 

It has to be going somewhere. Rent a radiator pressure tester from a parts store. The system should be able to hold 15 psi. If it doesn't, the you will have to try to find out where coolant is leaking.