Sounds like youve got steam in the cab from a leaking heater core. Is it a sickly sweet smell like antifreeze? You're losing coolant through the heater core and over heating.
Grab your radiator fan and move the top back and forth (not spinning, but towards and away from the engine). Is it loose? Look at the bottom of the pump, is it leaking from the weep hole (bottom of the casting towards the shaft). Finally, with the motor cold, remove the radiator cap and start the motor. As it warms up you should coolant flowing in the tank.
NEVER REMOVE THE CAP WHEN HOT.
If pump shaft is tight, not leaking, and you have adequate flow, your pump is fine. :Wink:
Monday, January 14th, 2008 AT 8:04 PM