The title says it all.

I have a 98 DX Hatch and at speeds anywhere from stopped while idling to about 20 mph, the radiator fan won't come on. It will let itself overheat until I speed up to 20+ mph. Sometimes will really act up and not come on until I hit 45+ mph.

I have replaced the:
-Fan Relay
-Fan Switch
-Thermostat
-Engine coolant temperature sensor

And nothing helped.

One thing I notice sometimes is that the car will vibrate for about 1-2 seconds (as if the fan came on) and then I can actually watch the temperature gauge go up semi-quickly.

Anybody know what's up?

 

Have you tried running power directly to the fan to see if it works?

Have you tried jumping the fan switch to see if it works?

 

Bleed the air out of the system
Ensure thermostat is operating correctly and nit on backwards.

 

I have, yes. It works fine that way. Also note that I replaced the radiator and flushed the system and re-filled it as well. (for other reasons)

 

How do I bleed it properly? I flushed it, refilled it, ran it hot, let it cycle then filled up it the rest of the way the next time it was cold.

Thermostat only goes in one way and the built-on seal has 2 notches that line up with the housing to ensure it only goes in the right way. It is also only a few months old.

 

Works which way? Those are two different tests.

 

Oh umm, it worked when jumped. Never ran power directly to it.

Forgot to mention in original post: fan switch is new too.

 

If it works when jumped at the switch, either the switch failed or you have a break in continuity between the fan and the switch. Given that it sent power if you bypassed the switch altogether (jumping the switch) you should be able to assume the wiring is fine and that the problem is the switch. The circuit is simply an on/off switch. Either it sends power or doesn't. If you want to verify you should pull the switch and see if there's any resistance when its probe is at operational temperature (simulate by placing it in boiling water like you would when testing a thermostat).

EDIT: Grammatical

 

I'll have to do some testing on the switch then. I'll look into it.

Also, I added a small detail into my original post if it makes a difference.

 

you said the fan is coming on at 45mph ?? the fan is useless at those speeds, i believe the cooling your seeing is the actual airflow through the rad, only way to test the fan operation is to let the vehicle sit and wait for the engine to get hot enough to trigger the fan, if the fan does not come on, yet you can trigger it by manually jumping the connector, i would suggest trying NEW parts, not new-to-the-car junkyard parts

 

You don't jump the switch, you jump the plug that goes to the switch. Are these oem parts you replaced them with or parts from a pepboys/autozone/advance auto/napa?

 

They are new. Never been used.

They are aftermarket brands but yes, from Autozone.