Russell Kent wrote:

Jerry Hey wrote:

Slightly off topic, but I just bought a l988 normally aspirated RX-7
which has a newly rebuilt engine and a clean radiator. It is
exhibiting cooling behavior which I don't understand, in that the
water temps are fine at freeway speeds but go up to near the redline
in stop and go traffic.  Fan seems to working properly--no bugs on
the rad.      Jerry

Paul responded:

That is strange Jerry. Check the thermostat. Somebody may have put in the wrong
kind. Mazda thermostat are unique. They close off a bypass passage when they
open. If the wrong kind is used they will not close the bypass passage and
at low RPM water pump speeds much water will be merely bypassed and not
routed through the radiator.

Easy test: while the engine is heading towards redline, try holding engine RPM up
around 3,000 with tranny in neutral.  If the engine temp falls, then Paul's theory
might be true.  If engine temp stays high, then it isn't the bypass thermostat.

Russell Kent

 
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