overheating while on highway

[toyo47]

I started driving my 1990 toyota corolla on the highway and the check engine light came on, my coolent temp. gauge started to go up towards hot.
i drove off the highway and temp gauge returned to normal, check engine
light still on. the vehicle only overheats when driven on the highway.
what could be causing this problem?

[mopars&corollas]

Have you verified at all that your gauge is working correctly? Did you check the water pump weep hole? That does seem a little strange, but I would start there if i were you.

[costadragon220]

^^ I agree then check the thermostat, gaskets etc are all good.

[FinalGear]

If I were you get that water pump change!

[gum_agile]

had experienced this problem before, overheating on a highway... check the aux fan for the radiator, the bearing should be spoiled/too loose that when running on a highway with strong external wind it suddenly stalls/stopped which causes the overheating.

try rotating aux fan blade by hand, if it rotates easily, should have problem.

[darcsyde]

the fan shouldn't kick on on the highway, check the radiator cap, make sure it's not loose, check thermostat, check fluid level, check for no leaks.

your car doesn't overheat when your off the freeway cuz your fan kicks on then

[Volksrod]

Check coolant level, then smell it, if it smells bitter you may have a head gasket leak.
Check for debris built up between AC condenser and radiator.
No fan is needed after 30mph.
Thermostat wax pellet may have leaked and no thermostat will no longer open fully.
If coolant is very old and acidic it may have eroded the blades right off the water pump and will no longer provide enough flow.
Check temperature across radiator face, any cold spots indicate a restriction.

[Bitter]

what was the check engine code?

[tashirosgt]

Gum_agile's remarks bring up an interesting question. When driving on the highway, does the force of the incoming air rotate the fan blades (of a fan with good bearings) even when the fan is off?

[midnightmach]

i vote thermostat...