Honda Accord engine coolant temperature high

I have a 1990 Honda Accord. The coolant temperature, if normal, is
right at the middle of the gauge. Recently, it has been as high as
4/5 of the gauge. I took it to a mechanics, thinking I might need
a new water pump. He checked it, told me the water pump was not
leaking, and did not change the water pump.

The thermocouple is fairly new, less than two years.

What might be wrong?

 

It would help to know how it behaves. Does it warm up in about 5 minutes but
climb steadily to 4/5 scale instead of half scale then level off? Does it
warm up to half scale, level off, then rise more slowly to 4/5 scale? Is the
reading steady or does it waver, and if it does, how much and how fast? Does
it read higher at idle or at cruising speed, or doesn't matter?

And although it may sound like a dumb question, I suppose the coolant level
is okay and the coolant isn't disappearing? And the heater does still work?

All these things help rule out some possibilities and identify the most
likely suspects.

Mike

 

and don't check the coolant by looking at the expansion bottle!
/always/ look inside the radiator after removing the cap.

 

did you replace the thermostat with a honda or oem equivalent one ?
most aftermarket place tend to sell the "regular" thermostat vs honda
failsafe.
"regular" version ususally failed closed so the engine can get overheat.
failsafe die open

if it is a failsafe version than i have no idea other than the coolant might
be low

 

I agree with the other posters that told you that the thermostat needs to
be changed--use a thermostat made by Honda. You should also check the
radiator water level--when the engine is cold. When I was very young--I
made the mistake of checking the radiator water when the engine was hot
and I have NEVER made that mistake again. I only check it in the morning
before I start the car.