87 Prelude runs too hot in heavy traffic

Hi,

I am new to this group and this question may have been asked before.

My'87 prelude SI runs great but in heavy stop and go traffic the water
temperature goes way up at 80% and then the fan engages and cools it down to
50% levels. In normal driving it is stable at 30% of the gage.

This has been happening for couple of years and I am wondering what could be
wrong. In the past the hottest the engine got was at the 50%. My mechanic
friend said that it is the fan switch. I had it replaced and the problem
persists.

Is there a thermostat that needs to be replaced? Could it be a sensor
somewhere else that is broken? I just replaced the vacuum next to the
distributor and oxygen sensor during a smog check.

The car has 190,000 miles on the odometer and I have been the sole owner of
the car.

Thanks for your help in advance.

 

I hope you have replaced the water pump at least once, if not, the
impeller may be worn. If the thermostat is original, try a new one
(Honda). Be sure the radiator is clean, and all the fins are still
strong. Proper antifreeze strength is important also. (50/50) bob