I have a 97 Express with a 4.3. In November, I noticed very little heat was coming from the vents.
First thing I figured was the heater core. Checked it, OK. I noticed the engine temperature was only
going upto the second large line on the temperature gauge (the one between 100 and 210 - there's
no number). Must be the thermostat. Bought a new one, flushed the system, new coolant. No change.
The air door for the heater core moves, so I know its not that. I then checked the hoses, they do not
get that hot. I use the van daily, as well as driving approximately 300 miles each way every few
weeks to get my son from college (just did it this weekend), and the engine temperature does not rise
above that line. I believe the gauge and sensor are working because the hoses do not get hot. Any
ideas? Thanks for any help.
Check your mechanical fan. It should be spinning much slower than your engine, or even staying still, if the clutch is performing correctly. If the fan is constantly on, this will limit coolant temp, not to mention rob fuel economy. Also check that your electrical fans are off unless commanded on by the AC system or when cooling is needed. If theyre always on, your ECT sensor is likely sending the wrong input to the computer and commanding the fans on too soon.
Which hoses are not that hot? If it's the heater core hoses, the core could be plugged. If it's the radiator hoses that are not hot, the thermostat could be stuck open.
You can back flush the heater core with a water hose, one way then the other, until the water comes out clean. Try not to let the water pressure going into the core get much over 20psi.
Thanks guys, I will check and let you know.
Ok I checked the fan, thank you Michael. Before I started the engine (it was cold) the fan was somewhat stiff. I could turn it, but when I let go, it would immediately stop. When I started the engine, it turned quickly - I could not stop it with my hand. After 15 minutes, the fan was rotating the same (fast -could not stop it) and the hoses are all still cold. after shutting the engine off, the fan stopped, and was the same as when I started (stiff). Should the fan spin freely, or is this normal?
With the engine off, you should be able to spin the fan easily by hand, but there should be slight resistance. It should stop spinning after one full turn or so. If it spins with no resistance and keeps going several turns then the clutch is bad.
I have changed the fan, it spins freely but there is no difference in the engine temperature. What else could it be? Thanks
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