I have a 2002 van that will over heat, but not throw any heat out the vents. Other times, it will run perfect until you stop, at which the temp willl climb a little and the air coming out if the vents will get cold. Increase RPM to 1000 and it will throw heat again, let off the throttle and it will throw cold. Again, intermixed with this is that fact it will start to overheat.

Do I have an air bubble in the system, bad water pump, or blown head gasket?

Thanks,
Todd

 

Low coolant level. Likely a leaky intake or head gasket. Or maybe water pump if your lucky (relatively easy fix) -could also be a stuck thermostat. Sometimes (as in my 98) the coolant evapourated on the block before it hit the ground). I loosened the rad cap off to remove the pressure and it didn't overheat as long as I kept the coolant up. Ran it this way for a year before I scrapped it -got another vehicle.

 

sounds like possibly weak water pump or restriction in hose flow somewhere check all hoses for a kink etc also the heater hoses above engine more towards driver side under cowl panel under hood see if any are kinked restricted

heater core may have corrosion dirt restriction as well

are both engine rad hoses same temp?

if not then stuck thermostat or non working water pump or plugging up radiator are there any hot and cold spots in it at the same time anywhere?

 

You are describing my cavaliers behavior. I documented my trials on this site to a successful end. The short version is i did all the usual stuff to no avail. I bypassed the heater core and it stopped over heating. BACK FLUSHING the heater core solved all my problems.