First check the top radiator hose. Is it hot when the engine is hot.
If not you have a sticking t-stat.

Second, unplug the radiator fan behind the fan and go directly from
the battery to the leads on the fan connector (the one connected to
the fan) and see if your fan turns. If not that is your problem,
replace the fan motor. With a car that old, the brushes in the fan
motor may be worn out. Recently happend to me.

But if it turns then you should check the thermoswitch. Trace the
wires from the fan motor to the t-switch and you will find it. should
be close to the t-stat housing, at least it is on the accord.

Frank

On 18 Jul 2005 12:14:40 -0700, "Bruce" >
wrote:

>I drove my '90 Civic EX sedan 1.6L (180k miles, 5spd) on a 65 mile trip
>last week (averaging 75mph, 3.5-4k rpm, no AC, ambient temp 85) and
>about 5 mins after I pulled off the highway, the temperature gauge
>slowly climbed to 2/3, up from its normal position at just under 1/2.
>Once I parked, I heard gurgling coming from the coolant overflow
>bottle. After about 4 hrs, I opened the radiator cap to check coolant
>level, it was still topped off even though about a cup leaked out of
>the top of the OF bottle. OF bottle was empty, however. I
>trepidatiously drove home, this time keeping my speed at 60mph or
>below, and had no problems.
>
>This was the first time since buying the car last fall I drove it at
>this speed for a prolonged time, have driven several 1/2 hr trips at
>less than 60mph since and no problem at all.
>
>There's no oil or HCs in the coolant, no coolant in oil, so I'm
>relatively confident there's not a head gasket problem, but who knows?
>This car's so old and only cost me $1000, so if that's the case it's
>junkyard time anyway. I plan on changing the thermostat, coolant hoses
>and rad cap this weekend, and possibly the thermal switch that controls
>the fan... don't recall ever hearing the fan run so that might be the
>problem right there (anyone know off-hand where this switch is
>located?). Perhaps the airflow at 70mph was enough to cool the engine,
>but after heavily taxing the engine for over an hour the flow at 30mph
>wasn't enough since the fan wasn't working? Maybe a collapsed lower
>hose? I changed the timing belt this spring and did water pump change
>then too... also, radiator is relatively new (according to previous
>owner).
>
>One other problem (maybe related, maybe not): I have noticed an
>intermittant squeal coming from the front left wheel that is in time
>with wheel rotation, and is more pronounced when I turn left. It's
>quiet during right turns, and whenever I apply even light brake
>pressure. This noise was very pronounced when it was running hot after
>the first half of my trip last week (only after I got off the highway
>and was driving for 5 mins at ~30mph on city streets). Possibly coolant
>leaking on brake pad/caliper?