I have asked questions about heat before. I have another question and or observation. My 533i has great heat and control now that I have replaced my mono valve again. Problem is when driving on the freeway at normal speeds the heat turns cold and has no temp control. As soon as I am in the city heat resumes and has temp control. Here is my question and or observation.
The heater has a temp sensor that is vacuum driven(sits under the drivers kick panel). Now I know that an engine has alot less vacuum when accelerating(hence fuel pressure increases via the fuel pressure regulator when vacuum decreases at the engine) So how the heck does your heater temp sensor function when engine speed is increased?
My car has a 3.64 posi diff so freeway speeds rpms are a little higher then stock 3.43 but not much.
Anyone have the answers to this. I have checked and or replaced vacuum lines and I do not have any odvious vacuum leaks and have replaced the inside temp sensor just as a afterthought.
Maybe I should wire in an electric vacuum pump that operates on its own instead of from the engine.
I know your probably thinking my thermostat is malfunctioning but temperature is always below the half-way mark on or off the freeway. Ant thoughts would be appreciated.

Cheers

• HEAT - euro635gas 2005-11-25 14:06:33 (547 views)
  • Just want to say thanks to everyone. This post helped me also. (nt) - cfisher 2005-12-07 13:14:23 (438 views)
  • Re: HEAT - spinedocab 2005-11-25 22:57:05 (455 views)
    • I'll check the valve (pic) - euro635gas 2005-11-26 13:00:37 (537 views)
      • Heat Fixed - euro635gas 2005-11-28 14:20:29 (439 views)
        • now that I have my heat actually blowing now, I think I have the same problem - Andrew Elmore 2005-11-28 17:58:17 (435 views)
          • Picts of valve install (pic) - euro635gas 2005-11-28 19:24:17 (453 views)
  • Have you checked the thermisters in the little housing by your left foot? - Roy In GA 2005-11-25 21:48:52 (445 views)
    • Re: Have you checked the thermisters in the little housing by your left foot? - kraigka 2006-01-10 19:34:15 (349 views)