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

 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.

 Paul Lamar

Check for the following condition:

If coolant level in the engine (not the overflow bottle) gets low, there can
be gas space in the circuit, and the water pump may not have enough
head/suction to get the water moving around the engine-radiator loop at low
rpm.  When you get to higher rpm, the head is overcome and the coolant
circulates.

This condition I have experienced on two different cars (not rotaries), one
with a slow head gasket leak, the other with a slow water-pump leak.

With the head gasket leak, the leaking combustion gases would force the
coolant back into the overflow bottle, displacing it from the engine.  Engine
would overheat at traffic lights, but cool okay when RPM went up.  Highway
was fine, slow up in traffic and the temp would start to rise right away.

Bill Schertz
KIS Cruiser #4045

 
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