MX-3.com

Hope you guys can help. 1992 MX-3, 4 cylinder, runs and drives great around town, but when running on the interstate it overheats. As soon as I get off the interstate it quickly returns to a normal temp. Fluids all look good. It has 2 electric cooling fans. Could one of these be not operating when things get hot?

Sounds like it is Head Gasket Time!

I'd almost say waterpump... but then it would overheat all the time.

These cars have issues with OVER cooling. Its pretty hard to overheat the 4 bangers.

Are you sure your fluids all check out? Burning oil or coolant? Any significant drips on the highway?

I have a 4 cyl. also and mine overheats after I get on it a little bit and then I sit at a stop light, or if i slow down and just cruise again it starts to overheat..it then cools down when i take back off...I changed the thermostat and made sure my fans are kicking on...but I am also burning through alot of oil....suggestions?

burning oil is either:

Head gasket/cracked head/leak in general - usually contaminates coolant or leaks on the ground - compression test will help identify this issue
-Valve guides - smokes a lot at startup but not much after that. Visible oil pool on intake valves if you remove the I/M - compression test wil help identifythis issue.
-Piston rings - Burns oil all the time. smokes plenty, lots of carbon buildup, blackened, maybe oily plugs, leads to clogged cat.... leakdown test will help identify this issue.

All oil burning issues should be accompanied by blue smoke in the exhaust. Should smell like oil too, obviously.

PCV valve / crankcase ventilation can also cause lots of oil burning.

Are your waterpump belts intact?
Is the coolant level good? In the motor too, not just the overflow.
Is your rad cap good?
Is your thermosensor good? The gauge on the dash is independently controlled by a single wire sensor.
Clogged passage somewhere?
I can't think of a reason the car overheats when cruising and not when idling.