View single post by Mark Rosenbaum
 Posted: 04-25-2007 04:47 am
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Mark Rosenbaum

Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
my75jh5 wrote: [...]At idle it will stay about half way, but driving and especially on the interstate it will climb to about 3/4 or a little more.[...]

Depending on the exact temperatures involved, that sounds to me like normal behavior for a JH engine in warm weather.  Under normal street driving conditions, coolant temperature will be about 100°F above the surrounding air temperature.  

Engine operating temperature is also sensitive to ignition timing.  If you set the timing at idle to somewhere between 8° BTDC and 12° BTDC, and plug the hose to the vacuum retard capsule, your baseline coolant temperature may decrease by as much as 20°F.

Some of the post-JH water pumps used in Lotus cars have improved impellers that offer much greater coolant flow.  One of these, and a bit of smoothing to the rectangular coolant opening in the engine block, should eliminate virtually any cooling problem not caused by a mechanical fault or gross mis-tuning of the engine.