[89IROC&RS]

well, first things to look at, is the cooling system all orignial/?? waterpump, radiator, hoses????? thermostat, all that stuff. if it is, my guess is a part failed.

but heres a test. jump in and drive the car around the block once or twice, then pull over with the engine running and pop the hood. there are pretty much five key parts to the cooling system the block(waterpump), radiator, thermostat, cooling fan system, and the hoses. with it sitting there idling, get out, check if your fan is on, if its not get in and turn your A/C on, then check again, your fan should be running. if its not, the fan is bad. if it is running turn the A/C back off. now, check for heat in the system. naturally the block will be hot, dont grab that. grab a hold of the upper radiator hose. is it warm?????? if it isnt, chances are your thermostat is stuck closed. if it is, move to the radiator and CARFULLY touch the cap, it SHOULD be HOT!! if its not, your radiator is probly clogged or something, if its hot, grab the lower radiator hose, is that hot??? should be if its not, probly also means the radiator is cool. now, if the upper hose is cool close to the radiator, but hot close to the block, you could have a bad water pump, and there is no coolant flow, and the coolant in the hose is being heated by the hot fluid coming out of the open thermostat. but there isnt enough heat transferrence to heat the coolant close to the radiator. if the cooling system is hot everywhere, and the fan isnt running while its overheating, it could be one or more of the following. the fan motor, which you can test by turning on the AC as stated above. the fan temp switch on the passenger side of the block above and in front of the starter motor. or the cooling fan relay on the firewall in front of the driver. hope that helps.