overheat only in stop and go

[Chris Covington]

All,

Picked up the 200q20v again after not driving it for awhile, took it to
Boston and all was well until I hit traffic at the 84/90 intersection and
then again outside the tollbooths around the city.  In traffic, the car's
water temp would rise to about the 1 bar away from the top of the heat
range and the red thermometer light would go off on the Autocheck.  It
never went any higher temp-wise, probably helped by my blasting the heat.
Could this be the rad. fan or the thermo, etc.?  How can I determine?  The
problem never happens during non-city driving.

Chris
'91 200q20v