Overheated Engine light comes on--but engine isnt overheated

capecodburban

New Member
Joined
Mar 13, 2011
Messages
1
Location
Cape Cod Mass
Car(s)
2001 Chevy Suburban
I have a 2001 Chevy Suburban. Out of the blue, the engine overheated light comes on, but when I open the hood, no steam, no boiling in the resevoir, the hoses are touchable but the temp gauge is pegged at 260. I let it sit in the driveway to cool down went inside for maybe 5 minutes, when I came out and checked the temp gauge was back to normal. There is no way it would cool down that fast from 260. Ive replaced the sensor, but its still happening. I dont know what else it could be. Any help would be appreciated!
 

Ford Prefect

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Dec 10, 2006
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1,872
Location
Bavaria
Car(s)
MINI, E30, GT86
This is just a total and complete guess, as I know absolutely nothing about your particular car, but the "gauge" in a Mini will indicate perfectly normal temperature as long as it's in a certain range. As soon as it goes slightly above that range it will indicate omfg I'm about to friggin explode. Perhaps your chevy is as "modern" as my Mini, and tries to make you completely paranoid.
 
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Spectre

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Feb 1, 2007
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Location
Dallas, Texas
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00 4Runner | 02 919 | 87 XJ6 | 86 CB700SC
Your thermostat or water pump has probably failed - if the radiator is not showing signs of overheating but the gauge is pegging, it is likely that there is no coolant flow. Check for a collapsing radiator hose while you are at it.

Next most likely failure is a headgasket.
 
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Spectre

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Feb 1, 2007
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Dallas, Texas
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00 4Runner | 02 919 | 87 XJ6 | 86 CB700SC
Well, if it wasn't before.... it might be now. :p

More seriously, there have been problems in some truck motors with the coolant used by GM in that era - including sludging and prematurely failed headgaskets due to chemical etching and erosion.
 
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NotLaw

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Mar 18, 2008
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473
Location
Cedar City, UT
Car(s)
'90 Saab SPG, '84 K5 Blazer, '67 Fairlane 500
My parents have a 91 GMC Safari that had a similar problem years ago, spent quite a lot of time and money trying to figure it out. Turned out to be a bad ground that we found while performing some routine maintenance.
We put an after market temp gauge in for a little while, IIRC, it screwed with the computer and the van did not run quite right, but it proved that the engine was not actually overheating. Put it back to stock and used electrical tape to cover up the warning light. Lived with it for nearly a year till we found the bad ground... (it was just a loose ground strap under the hood. why it only messed the dash up I don't know, but we cleaned up the strap and the place it bolted to, tightened it up, and the temp gauge was fixed.)
 
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tquattro

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Jun 18, 2008
Messages
1,089
Location
Transylvania
Car(s)
Audi A3 1.8T
I got a similar problem with my Audi starting about a week ago. The coolant/overheating warning light comes on after 10-15s after I start the engine, cold or hot engine doesn't matter. The coolant level was above minimum and I checked the coolant level sensor: unplugged the connector from the sensor->warning on, i shorted the two pins from the connector just to be sure-> warning still on. In my case, apparently, the Multi-Function Temperature Sensor(MFTS) is the culprit for the warning. This sensor has 3 pins: one for the temp gauge(works fine in my case), one for the ECU and AC control unit to disable AC in case of overheating(AC also works in my case) and a pin that goes to the warning light. I unplugged the connector from this sensor and the warning light didn't came on afterwards, I connected it back and then the warning was on again. I used the car this way for a couple of days and starting yesterday the warning light didn't came on again. Maybe the connectors were oxidized, but I will replace the MFTS this weekend and clean the connector just to be sure. In all this time the engine cooling system worked ok, except the warning light: coolant level above minimum, in stop-and-go traffic if the engine was getting hot the cooling fan started normally, AC worked fine.

I hope it helps.
 
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