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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

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Old 08-23-2013, 03:25 PM   #1
brlabrune

 
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Smile Faulty Temp Sensor...Or Not?

I've been experiencing an issue with my 91 LX 5.0 with a fresh 347. I have an Autometer Temp Gauge ILO the Factory Gauge. I can start my car and once it gets to normal operating temperature, it will continue to creep up to overheating temps (as the gauge would show) but there's one kicker, my flex-a-lite black magic electric fan (on-board thermostat controlled) doesn't kick in and my 185 degree engine thermostat isn't opening thus leading me to believe its truly not overheating. I have used 2 different temp sensors with the same result. The one thing I haven't ruled out is the method of connection to the temp sensor on the intake. The original black rubber boot connector was severed and I used a butt connector and crimped an extension to an eyelet connector and fastened it to the sensor with 2 nuts. Could this be the culprit? Anyone else experienced this?
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Old 08-23-2013, 03:39 PM   #2
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Where is your fan thermostat taking it temp reading at.

If you have the controller themostat pushed into the radiator and the engine thermostat is not opening then engine temp will climb with out the fan kicking on because the radiator is not hot enough.
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Old 08-23-2013, 06:39 PM   #3
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The fan sensor is pushed in next to the upper hose outlet. Its odd because the temp gauge will creep up to 220 and then the engine thermostat will kick on along with the fan. I have also burped the system to make sure all the air pockets would be gone from the coolant. Any ideas?
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Old 08-23-2013, 06:55 PM   #4
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If you are sure that your 185 thermostat is not opening then that is the problem.

If it don't open fully it will take a lot longer for the radiator to get to the temp to kick the fan on.

The gauge in the car gets up to 220 because it is taking the temp directly from the water jacket of the intake . So the engine temp is much hotter than the radiator because the thermostat is not opening.
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Old 08-24-2013, 09:41 PM   #5
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The engine thermostat does open after it hits about 220 on the temp gauge. I've used 2 new thermostats now with the same result. I'm on my second temp sensor as well.
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Old 08-24-2013, 10:29 PM   #6
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Go with after market gauge it will never let you down mine would go up and down for no reason
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Old 08-25-2013, 09:01 AM   #7
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Quote:
Originally Posted by oREDNECKo View Post
Go with after market gauge it will never let you down mine would go up and down for no reason

He has an after market gauge.



Op are you sure you have the thermostat in correctly and not backwards?

If seen pple put the thermostat in back wards caus they forgot witch way it was when taking it out

That would cause the engine to get much hotter that 185 befor it opens because the part that is supposed to be toward the engine pointing out in cooler water.


End with black arrow facing radiator , end with red arrow facing intake.

Click the image to open in full size.
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Old 08-25-2013, 09:03 AM   #8
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Also op if your getting thermostats from autozone , get one from NAPA ,

Ive blown through 3 thermostats from autozone before I got a good one.
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Old 08-25-2013, 12:27 PM   #9
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Well, I thought I put the t-stats in correctly but it can't hurt me to double check. I have been getting my sensors off ebay so will also give autozone a shot. Thanks for your help, I do appreciate it.
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Old 08-25-2013, 01:12 PM   #10
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stant ...t-stats, if el vatozone doesn't sell such, go elsewhere
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Old 08-25-2013, 01:12 PM
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