Why is Temp Gauge Pegging? - JeepForum.com

 
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post #1 of 5 Old 04-15-2017, 04:49 PM Thread Starter
Skerr
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1985 CJ7 
 
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Location: White Springs
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Why is Temp Gauge Pegging?

I have a '90 Cherokee with a '98 4.0. I installed the motor. Swapped everything over to Renix. It has a new, aluminum radiator, triple electric fans, 190* thermostat, new water pump, new hoses. Temp gauge in the cab is pegging at 260* when you put it into gear. Put it back in park and it immediately goes to 230*. My infrared thermometer is showing acceptable temperatures all over under the hood, hoses, thermostat housing (which is hottest at 230*), engine block, radiator. All of these areas, with the exception of the Tstat housing is at, or below, 210*. Running down the road, at highway speeds, and the temp comes back up to 260*. What should I be looking at?


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post #2 of 5 Old 04-17-2017, 09:07 PM
ou2mame
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Could it be a ground or other electric issue? My temps were reporting overheating when I put the headlights on, ended up being a corroded temp sensor plug.

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post #3 of 5 Old 04-18-2017, 08:35 PM Thread Starter
Skerr
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I've been all over under the hood and can't find anything amiss. I'll have a closer look at the temp sender plug though. Thanks for the idea.

Kerrdog
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post #4 of 5 Old 04-24-2017, 02:23 AM
oIIIIIooIIIIIo
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1988 MJ Comanche 
 
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Water temperature senders are poorly engineered. Is this the factory gauge? The trouble with factory senders is that they are variable resistance units and not thermocouple devices. Manufacturers use them because they are cheap and simple but accuracy leaves slot to be desired. The other thing I had with my 1988 Comanche is that the sender is next to the exhaust manifold. So what the gauge is reading is affected my the exhaust heat.


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post #5 of 5 Old 04-24-2017, 10:42 AM Thread Starter
Skerr
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Quote:
Originally Posted by oIIIIIooIIIIIo View Post
Water temperature senders are poorly engineered. Is this the factory gauge? The trouble with factory senders is that they are variable resistance units and not thermocouple devices. Manufacturers use them because they are cheap and simple but accuracy leaves slot to be desired. The other thing I had with my 1988 Comanche is that the sender is next to the exhaust manifold. So what the gauge is reading is affected my the exhaust heat.


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Glad you said that. It is the factory gauge, and I adapted the tstat housing for the sensor. The brass fittings make the sensor sit up higher, and the brass gets hotter than any other part of the cooling system. Maybe the exhaust is impacting it? Dang good info. Thank you.

Kerrdog
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