Ok im seeing 2 problmes with my 00 4x4 4dr. First off i never make the 195degree mark (which i believe is operating temp.) I can be crusing 70 on the interstate up and down hills for 30 min and barely break 155 degrees. Could this be my t stat? Also I think i have a vaccume leak because A. My dad swears he can hear it and B. when i change the climate controled air from face level to the floor or defrosters it still comes out the top (face level) too. I believe the acuators run off of vaccume if I'm corrrect. Any suggestions on where to start looking? Or jusk grab a can of break cleaner and have at it? Also could any of these things contribute to my spectacular 10-12 mpg city. Thanks
Michael

 

I would say best bet would be T-stat for the not reaching operating temp. I had the same problem and was stuck at the same temp about 160. T-stat fixed it for me. Plus the T-stat is easy and cheap to replace.

 

If your not up to operating temp, your puter doesn't control fuel to air mixture and your gas mileage will suck.

vacuum leak, yep. Check for a link in the Self-Help section on 4x4 no worky.

 

Both of these things will contribute to your lower than average mileage. It definitely sounds like your t-stat has failed open. When it is cold out, your engine will never produce enough heat to over come the heat dissipation of the radiator.

And it definitely sounds like you have a vacuum problem that is causing the HVAC system to not function properly. Notice I didn't say leak, although a leak could definitely be that problem. Being a 4wd vehicle, the vacuum source for the HVAC system is shared with the front axle actuator.

Does your 4wd work?

Here is the vacuum schematic for the engine:


For schematics of the dash vacuum routing and functions:
Manual HVAC Controls:

Automatic HVAC Controls:

 

Thanks guys, I picked up a T-Stat this afternoon. Swartlkk Thanks a ton for the schmatics. My 4x4 Does still work though. So i guess this eliminates a few possibalities.
I'll start checking tomorrow
Michael