Hi, I know that this has been covered here multiple times, but I have read numerous threads and I still cannot solve my issue.
I have a 2001 Screw. It has 175K and I am the original owner.
The air blowing from the heater vent never gets more than ~ 70 degs and I am about to freeze to death.

I have checked / replaced the following:
New water pump - the old one showed no signs of wear
Replacement Blend door - the actuator works and the door changes position like it should
New Radiator - The old one started leaking back in the summer and I replaced it with a dual core model.
Thermostat - original, never changed
Dash Temp Gauge - reads right in the middle while running


I have measured the temp of the input hose to the heater core @ 116 F and the output hose at 85 F.


Any ideas as to what could be the problem? How hot should the input hose to the heater core be?

Thanks in advance.

 

Change the thermostat. Inlet should be a lot warmer than that.

 

The fact that my temp gauge runs right in the middle kept me from suspecting the thermostat. I will change it tomorrow and let you know how it works out.
Thanks for the advice.

 

The temp gauge is not linear, it's an idiot "go-no go" gauge.

 

Hi,
I changed the thermostat (195 deg) earlier tonight. Unfortunately this doesn't appear to be the cause, there was no change in temp or behavior. I drove the truck for 1/2 hour and the temp gauge did not rise past half way. While the truck was still running, I could compress the top radiator hose with just hand pressure. Is this normal?
Anyone have any other ideas?
Thanks.

 

It must not be warm enough for it to build pressure. Your new radiator may be TOO efficient!

I wonder if your heater core is plugged - you can try pulling both hoses off and backflushing it with a garden hose.

 

I flushed the heater core this weekend. It did not seem to be clogged and faucet water pressure flowed right through it. I have also blocked the top 2/3 of the radiator with cardboard. All to no effect.
I am completely stumped.

 

Is your clutch fan constantly running full speed maybe?

 

Thanks for the advice. Could you give me some guidance on how to check the fan clutch?

 

Start a cold engine, get out and open the hood. Watch the fan. On start, it will probably run full speed and you will hear it howl. After a minute or so, it should slow down and significantly get quieter.