1992 Honda Civic Hatchback. 1.5 L. Car was overheating. Got home, opened rad. cap (after waiting 5 min), barely any coolant in radiator. Filled up with water and coolant. Turned on car, waited a while, rad fan did not turn on. Brought to mechanic's house and did everything as follows:

Replaced Radiator. Checked fan relay. Relay is fine. Replaced both sensors (one is on front side of eng block across from radiator, other is back of eng block) Both had signs of major overheating. The fan works fine when we jump the sensor switch on the back of the eng block sensor. The only item he hasn't replaced is the thermostat. Could this be the problem? Both the thermostat and the radiator were replaced in early April of 2010. The needle on the instrument panel read at the halfway point during all tests, even tho the radiator and hoses were super hot.
Any other ideas?

On a side note, this car was used for half the summer. not an everyday vehicle. I did, however, take the car roundtrip to Maryland (about 220 miles) 2 weeks ago, before this problem came about, last week. avg speed 70-75 mph to and from. I don't really push this car. I'm not a speed demon.

 

my guess is thermostat isnt opening..

(its new i said!)

it still happens.

take it out and drill the hole open a tad more on the thermostat and try to boil it in water to see if it pops open.

thermostat and fan switch work together....

 

You said you replaced both the sensors but im not sure what you mean on the back of the block? The fan switch is on the thermostat housing on the motor near the top radiator hose on the passengers side of the motor.

 

Ok, Every part of the cooling system has been replaced. This includes the Radiator, Thermostat, Temperature sensor and the Fan Switch Sensor (sits on the thermostat housing). Right now the connector to the Fan switch Sensor is jumpered so that the fan runs when the battery is turned on. my mechanic light tested the wires everywhere and the correct current is going thru. The Relay works. he tested it and found out that it never was the problem. I bought the radiator and thermostat from Adv Auto Parts, partly because they're still under lifetime warranty, so they were basically free replacements. The 2 sensors, I got from Autozone. I"m returning the Fan Switch Sensor and replacing it from one from Bap Geon (specialty Auto parts store). If this does not fix the problem, what else could it be? Any ideas?

 

Bleeding the cooling system:

1) Park the car on an inclined driveway with the front end higher than the rear.

2) Push the dash heater lever/**** to MAX heat.

3) Follow the directions in the diagram below (hint: the bleed bolt is located where the upper radiator hose connects to the engine):

 

oh, yah. We've done all that. I forgot to mention that. he's bled it every time we've had to refill the radiator reservoir. Pretty important forgotten detail. my bad.

 

I think the fan would kick on even if you had no coolent.. guess check your wires for the fan, check plugs and those pins, use some dielectric grease on terminals.. very odd somehow electricity is not getting to your fan so it should be easy to find if you have replaced everything else.