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Old Apr 22, 2009 | 12:05 PM
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Default C5 Overheated

Had a great trip into work today. About 5 miles from home, the C5 water temp shoots up to 260. I pulled over and waited for the temp to drop to the 200 range then headed back to the house.

Within a mile, temp is back up to 250, so I shut her down and wait again.

Within a few minutes temp is back to 210 or so, and everything is running normal. Head back home, and things are running smooth, then just before I get to the house, temp starts to climb again.

I'm thinking thermostat.
Any other ideas out there?
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Old Apr 22, 2009 | 12:10 PM
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Originally Posted by RENO
Had a great trip into work today. About 5 miles from home, the C5 water temp shoots up to 260. I pulled over and waited for the temp to drop to the 200 range then headed back to the house.

Within a mile, temp is back up to 250, so I shut her down and wait again.

Within a few minutes temp is back to 210 or so, and everything is running normal. Head back home, and things are running smooth, then just before I get to the house, temp starts to climb again.

I'm thinking thermostat.
Any other ideas out there?

I'm thinking plastic bag sucked up into radiator opening or fans not coming on.

Get down on your hands and knees and look up inside the radiator opening - hopefully it's as easy as taking out the plastic bag or paper that got sucked up in there !!

Good luck.
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Old Apr 22, 2009 | 12:33 PM
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Check the ground wire/pack located at the top forward frame rail adjacent to the hood riser. The fan grounds go through that. Mine came lose and caused exactly the same thing. Check fuses and/or verify the fans are running. Both will run at the same time, either in low speed mode or high speed.
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Old Apr 22, 2009 | 03:55 PM
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Small leak somewhere? Check fluid level.
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Old Apr 22, 2009 | 03:57 PM
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Originally Posted by Point & Shoot
I'm thinking plastic bag sucked up into radiator opening or fans not coming on.

Get down on your hands and knees and look up inside the radiator opening - hopefully it's as easy as taking out the plastic bag or paper that got sucked up in there !!

Good luck.
Easy check and I'll do this when I get home, but I think it's unlikely since it appears to be intermittent.
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Old Apr 22, 2009 | 03:59 PM
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Originally Posted by dgrant3830
Check the ground wire/pack located at the top forward frame rail adjacent to the hood riser. The fan grounds go through that. Mine came lose and caused exactly the same thing. Check fuses and/or verify the fans are running. Both will run at the same time, either in low speed mode or high speed.
This is a good candidate, almost everything else electrical works intermittently on that car, so the fans might be too.
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Old Apr 22, 2009 | 04:00 PM
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Originally Posted by MattB
Small leak somewhere? Check fluid level.
Definitely will check but it seems highly unlikely that this would cause an intermittent problem as described above.
Thanks for the input though.
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Old Apr 22, 2009 | 07:04 PM
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Originally Posted by RENO
Definitely will check but it seems highly unlikely that this would cause an intermittent problem as described above.
Thanks for the input though.
have seen it once where it seemed really intermitted, turns out it was just if you caught the thermostat right and it did or didn't open etc. Just needed coolant in that case.. good luck and let us know how it turns out
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Old Apr 24, 2009 | 02:21 PM
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Default running temp

Ok what's a normal runninng temp?
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Old Apr 24, 2009 | 09:31 PM
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Back in the old days I'd say a sticking thermostat...
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Old Apr 28, 2009 | 10:21 PM
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Finally got the chance to do a few diagnostics tonight.

Radiator is clear of debris.
Fluid level is fine.
As the temp goes up, the fans do come on, but the temp continues to rise.

So,
I'm back to either water pump, or thermostat.
When I get some more time I'll pull the thermostat and test it.
I'm hoping it's not the water pump.
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Old May 12, 2009 | 05:11 PM
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OK, after some issues, it turned out it was the thermostat after all. I replaced it then still had some trouble that turned out to be a big air pocket in the cooling system.

Who was the genius that decided there didn't need to be a cap ON the radiator???
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