Hi everyone, first time poster. I have a 98 Legacy 2.2 and the coolant fans won't come on no matter how hot it gets.  I disconnected the pigtail from the temp. sensor to check for voltage at the plug and when i turned the key to the "on" position the fans both came on. When I plugged it back in,  both fans shut off. The volt reading was 5 volts on one side of the pigtail plug, and 10 volts on the other contact. Does this mean the temp sensor is bad? Thanks for the help.

Make sure you check the coolant level in the radiator when it's cold.

Do you have good heat from the vents?

 

I've never checked the voltage at the sensor but yes it sounds like a bad temp sensor.

Yes, the radiator is full. The heat would sometimes turn cold so I changed the thermostat and now it puts out heat when it should.

Sounds like the sensor is telling the computer the engine temp is lower than it really is. When you unplug the sensor the computer sees a circuit fault and runs the fans continuously as a fail-safe. 

GD

Does it sound like the relays are all working then? I checked the fuses but didn't trace down all the relays and check them yet, I figured checking for voltage at the temp sensor would be enough. I remember reading somewhere the voltage at the sensor plug should be 5 volts which I have on one side, but wasn't sure about the 10 volts I read on the other side of the two-terminal pigtail. Is this cooling system designed to turn the fans on in case of a circuit fault? I couldn't find a decent schematic of this cars rad. fan system. Thanks

green connectors under the dash should test the fan circuit.

 

but maybe we're past that?

I hadn't heard about the green connectors. Where exactly, and what part of the circuit are they for?

Thanks

they will cycle the fans, various relays, for the evap system, etc..... as a test. I've never used them yet, but most Subarus have them, not sure about the 'modern' ones . They are small, green connectors tucked away under the dash somewhere - I think I have read of them sometimes secured to the steering column with tape?

 

 

 

Edited April 15, 20178 yr by 1 Lucky Texan

I'll check that out, thanks.

Anyone know where I can get a wiring diagram for this cooling fan system? Thanks

Fans work when you unplug the sensor. Wiring/relays/fuses for the fans is fine. Sensor is dead.

Thanks. Gonna change it today.

Now it's dong something different. Had my mom bring the car over so I could change the temp sensor (it's about a 30 mile drive) and when she got here the fans were both running and the temp gauge was halfway between H and C. So I didn't bother changing the temp sensor. I figured either I didn't get the engine hot enough to turn the fans on when I was first troubleshooting it, or by taking the elec. connector off the sensor (to check the voltage) and then putting it back on it fixed what had been a loose or dirty connection. Then when she left and was about 5 miles from her house ( a 25 mile drive) she went to turn the heater on since it was a little chilly and the temp. gauge immediately jumped up from half- way to full hot. This doesn't make sense at all since I always thought that turning the cars heater on can help to cool an overheating engine, but in this case it caused it to overheat. When she got home and called to tell me about it, the temp gauge had gone back to middle and the fans were running. Any thoughts?

did it overheat when she was at a light, waiting for a train, or parked idling? fan could be intermittent

 

have you checked the coolant level in the radiaotor? is coolant being pushed into the overflow?

 

do you KNOW the car has a Subaru style thermostat?

 

It started overheating while she was driving and as soon as she bumped the temp setting on the climate control from halfay to about 3/4. Not sure if she changed the fan speed or not though. I recently topped off the radiator but I noticed that when I took the radiator cap off it wasn't full to the top and the overflow bottle was will above the full level. I replaced the thermostat earlier and used an aftermarket model. Are those unreliable?

I'm also wondering about a head gasket issue. Although there's no oil in the water or water in the oil. Would a blown head gas cause coolant to be forced from the radiator into the overflow bottle?

Low coolant in radiator is bad. Excess coolant in overflow is bad. Cheap aftermarket thermostat is not good.

 

Failing headgaskets typically do NOT mix coolant into the oil on subarus unless they are very fully blown. If run for a long while with the beginning failure, the continual slow leak of exhaust gasses will leave traces of black stuff in the overflow tank.

So with the fluid low in the radiator and high in the overflow, does that mean it's a blown head gasket? I haven't noticed any black stuff in overflow but will check.

So with the fluid low in the radiator and high in the overflow, does that mean it's a blown head gasket? I haven't noticed any black stuff in overflow but will check.

 

 

I would say 'quite likely' . But, personally, I'd have enough doubt to try a quality rad cap and a soob-style t'stat  (there ARE aftermarkets with the larger capsule so, depends on what you actually installed) before condemning a 2.2

 

often, when the car is overheating from a bad HG, there will be visible bubbles in the rad or overflow.

 

if it was an early 2.5, yeah HGs.

 

 

there are other guys here though that could guide you better I think.

Edited April 20, 20178 yr by 1 Lucky Texan

Will you see bubbles in the radiator and bottle the whole time the engine is running, or is it off and on? And would a faulty thermostat cause excess water in the overflow?

The black stuff takes months to build up. And getting one to run for months with the beginning failure takes very close monitoring of the coolant level. Like checking before every drive.

 

99 % of my experience is on the older ea82s. It Takes a good few days of close monitoring to determine for sure if it's the headgaskets pushing the coolant onto the recovery tank. A recent thread seems to have semonstrated that a bad radiator cap can cause similar symptoms on some models. There are other similar threads with the details.

thanks, I'll try replacing that cap.

Do the aftermarket thermostats quit working completely , or just sometimes?

The aftermarket ones have smaller valves. Probably restricting flow more than stock ones. The cooling system is the weak link in these cars, so I don't mess around. Oem or high end Stant only.