[Jermo]

So Saturday my upper radiator hose blew off at a stoplight. Made it the rest of the way home without over heating. Decided to replace radiator hose, thermostat, and coolant temp sensor. All changed, cooling system bled, and now my fan won't come on. Checked fuse, its good. Fan comes on with a/c and defrost, but at an idle, no fan. Cars not overheating while I'm driving, and I never really sit for very long in traffic. Any suggestions would help, going to put relays in tomorrow, but not real sure what else to do
Please help.

 

[Gamer92]

So Saturday my upper radiator hose blew off at a stoplight. Made it the rest of the way home without over heating. Decided to replace radiator hose, thermostat, and coolant temp sensor. All changed, cooling system bled, and now my fan won't come on. Checked fuse, its good. Fan comes on with a/c and defrost, but at an idle, no fan. Cars not overheating while I'm driving, and I never really sit for very long in traffic. Any suggestions would help, going to put relays in tomorrow, but not real sure what else to do
Please help.

What year and what motor do you have?

 

[Jermo]

96 lx 1.9l

 

[Gamer92]

96 lx 1.9l

Do you have access to a scan tool with live data capability?

I'm not sure how OBD 2 2nd gen cars are but on the third gen cars the fan comes on right around 220 degrees Fahrenheit.

 

[denisond3]

If the fan comes on with the a.c. or defrost on, then the fan - and at least one of the relays is good. (I think the fan comes on 'high' with the a.c. being on, but not sure if that means the low speed relay is working.) And its the PCM that tells the fan to run, when the a.c. or defroster is working - and the same PCM tells the fan to come on when the coolant temp sensor (on the metal tube on the line running back to the heater inlet) thinks the water is above 215 or so. So I would check the contacts in that sensor and its connector & the wires disappearing into the harness. The sensor is sort of hidden below the large rubber air inlet duct going to the throttle body.
There is also a relay inside the fuse box beside the air filter housing, but if that relay and the fuse near it are bad, the fan wont run at all.

 

[Jermo]

I changed temp sensor (the one with 2 wires, not the gauge sender). And if I run a jumper wire from one side of temp sensor harness to the other three fan comes on. Which relay is low and which one is high, ones blue, others black.

 

[FordMan59]

Is the engine overheating at idle? Sounds like the engine isn't getting hot enough for the ECU to call for fan operation. Either checking engine temperature with a live data scan tool or with an infrared thermometer should give you a good indication whether there's a problem or not.

 

[Jermo]

Hooked it to scanner at work car never gets above 212 and still no fan. But it idled, for almost 2 hours, not over heating just, chillin, never over 212 degrees. Do I have an overcooling issue, or a bad pcm?

 

[Gamer92]

Hooked it to scanner at work car never gets above 212 and still no fan. But it idled, for almost 2 hours, not over heating just, chillin, never over 212 degrees. Do I have an overcooling issue, or a bad pcm?

What brand was thermostat

 

[FordMan59]

As long as the engine temperature isn't getting any hotter than that, I think that it's just not getting hot enough to activate the fan. You know the fan works with the a/c on or when you run a jumper across the the wiring harness terminals for the coolant temperature sensor. Seems to me the only possible problem would be a bad ECT and you just replaced it, so I think the engine just isn't getting hot enough that you need the fan. 212* is boiling point for water, once 50% coolant is added it greatly increase boiling temperature.

 

[ShakeZilla19]

Plus you have about 16psi, over atm, in the cooling system. Could easily hit 300*F before boiling.

Running Escorts on the cold side is not a bad thing. The fan should kick in at 217*F. Next time you have it up to temp give it some gas to heat it up.

 

[FordMan59]

According to the aftermarket temperature gauge, I've seen my '88 Pony run as high as 240-250* on 100*+ days in city/stop and go driving, that was with the fan running and it didn't overheat. In my previous post I didn't even think about this being a pressurized system.

 

[Jermo]

I think the thermostat is a murry

 

[zzyzzx]

Murry thermostat?? Never heard of it and wouldn't use it either. Are you sure it's not a Motorad? Those thermostats suck.
Can you put the old thermostat back in? Was it broken too? A thermostat is not a PM item.

If I understand you correctly, you go the thermostat housing off without breaking a bolt???

 

[Jermo]

Yup, this is the second time I've changed the thermostat in my wagon. Helps alot to anti seize the hardware when you have it out.