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Old 08-07-2012, 10:36 PM   #1
Bad Noodle
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Default Temperature randomly fluctuates

Just bought a 99 forester. On the way home, the temp gauge started fluctuating randomly. I'd come to a stop, it would shoot up, then drop down. Or it would stay up for a while. Or it would go up when just driving. Tried to turn the heater on to relieve the readiator, but found that it got warm then tuned cold. noticed when it turns cold, the temps shoot up. I've read through the other threads, but wasn't sure the other threads, not sure what the best way to tackle this problem:

Bad Thermostat ?
Bad Water pump?

Probably not a bad head gasket as it would have to be sever and I don't have any coolant in the oil and don't have any white reside on the oil cap.

What would you guys recommend?
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Old 08-07-2012, 11:01 PM   #2
cal_look_zero
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Bad T stat for sure. Cold heater is a giveaway for that. Get a stant xact-stat or OEM. Don't buy a parts store replacement. Not sure why eactly, but Subis hate cheap t stats.
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Old 08-07-2012, 11:48 PM   #3
mod maniac
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When the heater stops working there is no water in it. You either have a leak or a bad hg. subaru's usually don,t get water into the oil when the hg is bad.
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Old 08-08-2012, 07:36 AM   #4
Bad Noodle
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Quote:
Originally Posted by mod maniac View Post
When the heater stops working there is no water in it. You either have a leak or a bad hg. subaru's usually don,t get water into the oil when the hg is bad.
This. I drove 40 miles and lost all the fluid in the radiator. No visible leaks when the car is off or idling, which leaves me with the head gasket.
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Old 08-08-2012, 10:15 AM   #5
Bluefoton
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Well if you lost all fluid while driving there might have been nothing left to leak out
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Old 08-08-2012, 10:49 AM   #6
Bad Noodle
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Quote:
Originally Posted by Bluefoton View Post
Well if you lost all fluid while driving there might have been nothing left to leak out
Checked multiple times with full rad at idle before going on test drive
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Old 08-08-2012, 07:41 PM   #7
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I wonder if your water pump is starting to die. Even if the thermostat is stuck open, the heater should still have hot water going through it. If the water stops circulating, the heater will cool off. But a sure way to tell is to remove the thermostat and put it in a pot of hot/boiling water and observe. It's the cheapest place to start.
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Old 08-11-2012, 05:08 PM   #8
giosoccer20
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I have this problem of a fluctuating temp gauge, it goes from normal to high, then when i drive over 30mph it goes back down to normal -_-. I don't get it at all. But I have actually found a visible water leak, and the CEL is on.
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Old 08-12-2012, 05:09 PM   #9
AWDmonk
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Quote:
Originally Posted by Bad Noodle View Post
This. I drove 40 miles and lost all the fluid in the radiator. No visible leaks when the car is off or idling, which leaves me with the head gasket.
Could be a slow leak not related to the head gasket. It's possible that when you checked the rad, all the coolant was in the block. Fill up the rad and bleed the system a couple times.
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Old 08-12-2012, 11:02 PM   #10
Bad Noodle
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Quote:
Originally Posted by AWDmonk View Post
Could be a slow leak not related to the head gasket. It's possible that when you checked the rad, all the coolant was in the block. Fill up the rad and bleed the system a couple times.
10-4 did that and still the same result before I drove the car I made sure the system was 100% free of air. Then I found a couple service bullitins in the na thread describing this common problem.

Apparently if you have an external leak, it can be fixed with the coolant conditioner according to subaru. But if you have an internal leak, you will see no signs except the symptoms I'm seeing.
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Old 08-13-2012, 01:15 PM   #11
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Quote:
Originally Posted by giosoccer20 View Post
I have this problem of a fluctuating temp gauge, it goes from normal to high, then when i drive over 30mph it goes back down to normal -_-. I don't get it at all. But I have actually found a visible water leak, and the CEL is on.
Check your rad cap or just get a new one, they are cheap. If it can't hold the pressure you will see high temps at low speeds but once you are at higher speed there is enough cooling to keep temps down.

As for the OP I think you may have multiple issues. Start with the cheap and easy and work down.
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Old 08-13-2012, 04:06 PM   #12
mod maniac
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Quote:
Originally Posted by Bad Noodle View Post
10-4 did that and still the same result before I drove the car I made sure the system was 100% free of air. Then I found a couple service bullitins in the na thread describing this common problem.

Apparently if you have an external leak, it can be fixed with the coolant conditioner according to subaru. But if you have an internal leak, you will see no signs except the symptoms I'm seeing.
That is exactly the way I see it all the time. hg's
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