C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Running hotter now. Why?

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Old Jan 19, 2005 | 07:41 PM
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Default Running hotter now. Why?

1985 Coupe.
Installed the short throw shift kit today. (Thanks LD85! Works great!)
I have been trying to stop some oil leaks, and have fixed most of them.
While trying to look at the front intake mainfold seal, I noticed a sensor plug(the one in the intake right above the block seal) was off. After much effort, I got it back on. That took care of the SES light
I head home, and after a mile or two, I notice the temp is around 205. It usually runs between 192 and 200. It got as hot as 212 while at a stoplight, but once I got moving it came back down to 200 or so. I don't recall whether the fan was running or not, but before I believe it ran all the time. I do know it came on as soon as I started the car.
My question. Does that sensor control when the fan comes on? I do have a service manual, but it is at the shop. Thought I would give you guys a shout before I head back down there.
Thanks,
Mitch
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Old Jan 19, 2005 | 07:50 PM
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Well with the coolant temp sensor disconnected, the ecm was probably in "limp home" mode and running the fan all the time. Unless the '85s has no ecm interaction with the fan.
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Old Jan 19, 2005 | 08:12 PM
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Originally Posted by MaxLean
Well with the coolant temp sensor disconnected, the ecm was probably in "limp home" mode and running the fan all the time. Unless the '85s has no ecm interaction with the fan.
The ECM DOES control the main fan on an '85. There are two connectors, side by side, where you described. One is the temp sensor for the ECM, as addressed. The other is the cold start switch for the 9th injector.

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Old Jan 19, 2005 | 10:33 PM
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Originally Posted by MaxLean
Well with the coolant temp sensor disconnected, the ecm was probably in "limp home" mode and running the fan all the time. Unless the '85s has no ecm interaction with the fan.
In other words.... Its running normal now.
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Old Jan 20, 2005 | 12:02 AM
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And even if the "elevated" temperatures weren't from the disconnected sensor, 205 degrees is nothing to worry about. Neither is 212. I'd start to worry when you hit temperatures in the 230's and up.
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Old Jan 20, 2005 | 12:32 AM
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Originally Posted by 85 500 horse
And even if the "elevated" temperatures weren't from the disconnected sensor, 205 degrees is nothing to worry about. Neither is 212. I'd start to worry when you hit temperatures in the 230's and up.

Yeah, I knew the C4s ran hot.
I did change my radiator not too long ago, and the tubes are a little wider than the original. I just figured that was why I was getting a little lower temps.
What exactly does "limp home" mode do? By the sound of it, it would curb the performance of the engine until whatever problem was fixed and the ECM reset. I haven't had any performance problems with the car. It has always run like that scalded-a$$ed ape.
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