Hi I have a 1989 honda civic Ef hatch. It's an si so the 1.6 engine. Okay so one day when I was driving the car started steaming from overheating ( temp gauge read normal) and when I pulled over I could hear the overflow bubbling like crazy. So I figured out that my thermostat wasn't opening up at the right time so I just took it out completely for now. Then I realized my fan is not turning on. Although it does work because I tested it with some speaker wire directly to the battery. I got a new temp sending unit for the fn and gauge well at least the mechanic I talked to said there's only one temp sending unit that works for both but when I replaced it neither the fn nor the gauge started working. And my car doesn't seem to be overheating at all even though I can't see the actuall temp I check the radiator cap to see if it's very hot and it's never more then warm. But my overflow still bubbles almost Everytime I stop driving the car. Even with a ten minute drive. Any ideas? P.s. It's not a blown head gasket. No coolant in oil and no oil in coolant doesn't pour out blck smoke either

 

already had the same issue with the bubbling, it was the head gasket, there was no coolant in oil and no oil in collant.

the gasket was just leaking air in the cooling system.

 

I also just had a head gasket failure last year on my car. Mine was "bubbling" the overflow tank too.

I also had no discernible oil in coolant or coolant in oil. I drove it for weeks that way and kept having to top the coolant off every few days. One day it eventually filled a cylinder with coolant completely and hydrolocked the engine and it wouldn't even crank. Had to tow it home. At this point I did a full oil pan drain and definitely had milkshake oil. But weeks prior when the car first overheated and had the boiling overflow tank I couldn't detect any coolant on the dipstick.

Thankfully no bent rods or anything

 

There are two temperature sensors as far as I know, one for the guage cluster and one for the fan.

 

I had bubbling in the overflow tank of my previous hatch, during the summer, and it was just a bad radiator cap. To test for head gasket issues, buy the Napa block tester. Everyone was telling me it was the head gasket but that test told me it wasn't.