1. Does the electric fan engage in low and high speed. (check by removing and jumpering leads on Radiator sensors)

2. Do the rad sensors activate 'on spec'. Check by removing sensor and check w/ ohm meter in pot of warming water on stove. Also, these switches carry the full current load for the electric fan, so over time the contacts become pitted and corroded, and may 'test' fine but not carry the load (slow fan speed).. IMHO, replace both. While you are at it, go to a set of lower switches so the fan activates earlier.

3. There is a small line running from the rad top to the o'flow bottle. Is there a good '4-beer flow' going into the rad overflow bottle. If not the purge nipple on the rad is plugged.

BE CAREFUL !!!!!!!!!!!!!!!!!!!!! whilst removing the small line from the rad nipple. . It gets VERY !!! brittle It is best to slice / trim the hose off ... DO not twist or pull hard !!!!!! A broken nipple canbe repaird. but it ain't fun.

4. Does engine driven fan 'clutch up' at about 180ºF ? if not, replace it.

5. On the coolent level switch in therad o'flow bottle, remove it from the bottle, clean off the crud, test and re-install. Replacements are not that expensive. Check with S*teve Hay*good for a replacement. cheers.. js

Regards

John Stein
edgewater24.com

• Running hot/Coolant light on? (pic) - mbw635 2007-05-23 18:54:39 (644 views)
  • Several things to check.... - johnhstein, 85-M6CSi, 85 745i & 84 633CSi 2007-09-18 07:25:37 (293 views)
  • Re: Running hot/Coolant light on? - downernsp 2007-06-01 17:35:54 (431 views)
  • Re: Running hot/Coolant light on? (pic) - Ken Mc Lean - 85 635CSi 2007-05-26 22:48:54 (517 views)
    • 75 and 71º t-stats are nothing but trouble... - johnhstein, 85-M6CSi, 85 745i & 84 633CSi 2007-09-19 07:40:32 (292 views)
  • Re: Running hot/Coolant light on? (pic) (url) - cwsixer 2007-05-24 00:37:27 (533 views)
    • great link,thx (nt) - dr750 2007-05-27 08:32:12 (455 views)
  • Re: Running hot/Coolant light on? - crovensto 2007-05-23 21:24:09 (477 views)
    • If it's not the gauge do a leak down test for bad head gasket. - bmw635 2007-05-24 00:37:28 (437 views)
      • Thanks - mbw635 2007-05-24 23:13:19 (410 views)
        • Running Hot: Problem Solved - mbw635 2007-09-16 21:03:32 (333 views)
          • Hmm, too simple for too much headache. :-)) (nt) - bmw635 2007-09-18 01:47:55 (307 views)