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91 Taurus Vulcan Temp/Radiator Fan/ECT Issue? Hmmm

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Joined: Sat Mar 24, 2012 1:23 am

91 Taurus Vulcan Temp/Radiator Fan/ECT Issue? Hmmm

Post by GT2AV8 » Sat Mar 24, 2012 2:18 am

Hello, all! I have a '91 Taurus w/ the 3.0 Vulcan. It has about 180k and runs/sounds like it's brand new. It has been sitting around mostly for the past year or so (though started every 2-4 weeks, generally) since a dog hitting accident (he survived... after a ride in the back seat to the emergency vet and an $800 bill that, thankfully, the owner did reimburse). ANYWAY, so I'm getting it back on the road and I have a question about an engine temperature/rad fan/possible ECT sensor issue.

Standing still or in frequent slow/stop/go traffic, the temperature needle climbs (temp sending sensor was replaced a few years ago and gauge follows heat up/cool down/drive temp appropriately). The dash gauge reads with brackets at low and high and "N O R M A L" written across inbetween the brackets. Maintaining speed, the needle hangs around the O consistently. When I get to a stopped (or REALLY slow driving like heavy traffic) it climbs up to around A, then at some point the radiator fan starts (only ever runs on low speed), and it comes back down to maybe around the R area. Then, if I continue idling it kicks back and forth with the fan coming on around A, cooling to R, fan off, climbing to A, and so on.

Radiator is new. Water pump is young'ish. Thermostat is (195 degree) about the same age as the pump, and tested today... works perfectly and looks brand new. Coolant is as clean as it gets and is proper mixture. System is free of air.

- If I pull the plug to the coolant temperature sensor (ECT), the rad fan runs on high. With the sensor plugged in, the fan doesn't start until the dash gauge is at A, and then only runs at low speed until it's down to about the R. I can't check whether the rad fan coems on with the a/c working, as it is the ONE thing that doesn't work on the car.
Multimeter findings (ohms between sensor terminals):
- Engine @ ambient temperature, 31.6
- Running after warmed up without ECT plugged in (around the O on gauge), ranged from 6-10.
- Just after running it WITH the ECT plugged in (gauge on A), 2.2.

- Is the ECT sensor bad? The findings with the multimeter seem fairly on par, without a way to compare them to known temperatures. BUT, could it be that the sensor is functioning, but not relenting resistence at low enough temperatures? Sort of behind the curve. Is that possible for an old sensor? Since the rest of the chain seems to be working (the fan does eventually come on), I'm inclinded to think that, maybe.
- If it's likely not the ECT sensor, what could it be?

- Is there anything wrong at all, or is it normal for it to climb up into the A (sometimes when hot maybe approaches L, though it has been so long, I can't say for sure)? Even if that temperature range is normal (yes, I know it says NORMAL, haha), it seems to me that it shouldn't be bouncing around like that and should be starting the fan earlie to maintain a more constant temperature.

Also, it did has some pinging at low rpm acceleration... but, I have cleaned the MAF, lightly cleaned the throttle body, Seafoamed into vacuum to intake, and that seems to have cleared the pinging, and dare I say, it seems to have more power, but maybe I'm fooling myself.

Thanks for any input!! I just discovered these forums, and am really happy to see them, and so much enthusiasm about the Taurus. I had no idea. It's a great car, truly. I also drive a Jeep, a Sequoia, and a Miata, and I love the Taurus equally, especially for traveling.


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