hi i am new to the forum! Read some threads but would like some advice.

Scenario: 94 honda civic sedan 1.5, runs hot when it wants to, never let it get over halfway mark without turning off and cooling down so I dont mess up the head. The water is boiling into the reservoir when it wants to. It overheats with the AC on/off and is sporatic. Sometimes you can drive 10 miles and it will happen or drive 40 miles then it will happen. Have let the car sit idle, in 104 degree weather for 2 1/2 hours and it wont run hot at all, then drive it for 12 miles and it starts bubbling in the reservoir. All of a sudden started!

Things we have tried: changed the water pump and timing belt, thermostat, and radiator cap....bled it out....checked for blockage....

No signs of water in oil, smoke or water out of exhaust, no leaks, no smell of anitfreeze, no coolant around the spark plugs..

we are about to go outside and straight wire the fan, fill it up, then test drive it...

 

1. Make sure it's full with Coolant in radiator and the reservoir.

2. Make sure the fans come on.

 

Sounds like bad head gasket if it is going into resivour. Air is getting in system causing pressure which causes overflow to prevent exploding raditor. Head gasket is the most common place for air to leak in. Run car with radiator cap off (carefully), do bubbles keep coming up? Then it is head gasket. Hard think to accept but the more i look around the more i am convinced that this is becoming a common problem with old civics.

 

Yes both fans are running and no there are no bubbles coming out with the radiator cap off and the car running.

 

If it overheats only when sitting still or in slow traffic, it could be that the fan is not always coming on. The fan switches can get flakey. Unplug the switch and jumper the wires in the plug to force the fan on all the time the key is on.

On that model the A/C condenser and radiator are completely separate, only the radiator fan works to cool the engine.

 

you might want to try replacing the thermostat if the fan is working

 

Has anything been done to the radiator? What's the condition?