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My sons 2000 Outback
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Discussion Starter #1
My son tells me that he starts his car and waits a while for it to warm up a bit, not to full operating Temperature. He puts it in Drive and as he accelerates he watches his Temp gauge rise into the red zone.
He has opened the hood at this point and does not get the sense that it is overheating. No HOT HOT smell, he can touch the radiator and other parts of the engine that would indicate Overheating.
I wonder if a faulty Temp Sensor would be Voltage critical and maybe the acceleration raises the Voltage a bit over an idle driving the sensor to give a high reading. Any thoughts?
P.S. no coolant in Oil or oil in coolant so the Head gaskets seem happy.

Where is the Temp Sensor on the 2.5?
 

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2008 Subaru Outback 2.5XT, DDM HID 5000K, K&N, Yokohama Avid TRZ, Curt Hitch, Subaru All Weather Mats, Sirius
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Tony - I don't know exactly where the temp sensor is.

I would check out 2 things

1) Thermostat - when was this replaced?
2) Water Pump - Was this done at all?

If the system is not opening or fully allowing all coolant into the radiator you may see the radiator fel 'normal/ not too hot' while the engine itself it getting quite hot from the trapped or restricted coolant.
 

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2001 VDC/SC One of a Kind
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The temp sensor is on the crossover pipe under the intake manifold. Look to the right side of center. There are two sensors. A two wire sensor for the computer and the single wire for the gauge. Both screw in with a 19mm.

It is possible an electrical spike could cause the gauge to act irrational with a failing sensor.

Also check your coolant level and insure its full.
 

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DIY-Turbo 2.2l OBS 12.89s 1/4mile @ 106.17MPH
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The temp sensor is on the crossover pipe under the intake manifold. Look to the right side of center. There are two sensors. A two wire sensor for the computer and the single wire for the gauge. Both screw in with a 19mm.

It is possible an electrical spike could cause the gauge to act irrational with a failing sensor.

Also check your coolant level and insure its full.
+1 coolant temp sensors are on the x-over pipe under the intake manifold.

If the overflow bottle rises when car is hot & drops back down to the base level when the car is cold you should be OK
BUT
If the coolant in the overflow bottle rises until it overflows / engine is not pulling coolant back from the overflow bottle when it is cold = a sign of a blown HG.
 

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My sons 2000 Outback
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Discussion Starter #5
Tony - I don't know exactly where the temp sensor is.

I would check out 2 things

1) Thermostat - when was this replaced?
2) Water Pump - Was this done at all?

If the system is not opening or fully allowing all coolant into the radiator you may see the radiator fel 'normal/ not too hot' while the engine itself it getting quite hot from the trapped or restricted coolant.
Coolant, Thermostat and waterpump changed about 6 K miles ago when I did the Timing Belt
 

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My sons 2000 Outback
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Discussion Starter #6
The temp sensor is on the crossover pipe under the intake manifold. Look to the right side of center. There are two sensors. A two wire sensor for the computer and the single wire for the gauge. Both screw in with a 19mm.

It is possible an electrical spike could cause the gauge to act irrational with a failing sensor.

Also check your coolant level and insure its full.
I see a three contact Coolant sensor.. Funny how they do not require Coolant Draining. I must have to drain it off a bit so it doesn't come out with teh sensor out.
 

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DIY-Turbo 2.2l OBS 12.89s 1/4mile @ 106.17MPH
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I see a three contact Coolant sensor.. Funny how they do not require Coolant Draining. I must have to drain it off a bit so it doesn't come out with teh sensor out.
Coolant bridge is nearly the highest point of the coolant system (radiator filler neck is only area that is higher) + the coolant temp sensor is small enough that there should not be much coolant lost if you have the new sensor ready to go on the car as soon as the old sensor comes off.

Removing the upper radiator hose & draining the coolant in the bridge/x-over / upper rad tank will allow you to remove the cts with no coolant spilling on the block.

Note: Your PDF is showing the coolant temp sensor that goes to the ECU there is also usually a 1 wire sensor that is for the gauge - may be worth taking a look @ your coolant bridge/x-over to make sure this is the only coolant temp sensor on your car
 

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newer (what years?) have a single 3-wire sensor.
 

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My sons 2000 Outback
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Discussion Starter #9
Coolant bridge is nearly the highest point of the coolant system (radiator filler neck is only area that is higher) + the coolant temp sensor is small enough that there should not be much coolant lost if you have the new sensor ready to go on the car as soon as the old sensor comes off.

Removing the upper radiator hose & draining the coolant in the bridge/x-over / upper rad tank will allow you to remove the cts with no coolant spilling on the block.

Note: Your PDF is showing the coolant temp sensor that goes to the ECU there is also usually a 1 wire sensor that is for the gauge - may be worth taking a look @ your coolant bridge/x-over to make sure this is the only coolant temp sensor on your car
YES... I am looking for the one for te gauge since the car is running fine, no false cold running messages sent to the ECU.
Did some years have the two sensings combined? I'm wondering because that seems to be teh onlt sensor that pops up when I query "Coolant Sensor"
 

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2001 VDC/SC One of a Kind
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There are two sensors. One is for the computer, 2 or 3 wire, the other is a single wire thermometer that is in close proximity to the one for the computer. I've attached a wiring diagram.

As for the location, it a bugger to get at with the PCV hoses attached.
 

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Discussion Starter #11
Thanks for the diagrams... very helpful
 
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