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View Full Version : Temp gauge reads hot with thermostat and runs at 210 w/o thermostat


CTRacing
April 16th, 2012, 18:12
Is my gauge bad? I checked with a IR meter and it read under 200 when the gauge was reading a little above 210. How can I check that the water temperature gauge is still good?

Tim_MN
April 16th, 2012, 18:56
The gauge on the dash is not a calibrated scientific instrument, it's just a dash gauge. The difference between about 200* and about 210* is about 5%, which is within reasonable expectations for a dash gauge. Is your IR temp gun calibrated or certified ?

The Coolant Temperature Sensor can be tested, or for about $25 you can replace it.

Talyn
April 17th, 2012, 06:09
You don't state your year, but there could be two sensors. Also, it depends on where you are checking the temp.

O-Gauge Steamer
April 17th, 2012, 07:21
Also, if you checked it at the T-Stat housing, there is a lossdue to the aluminium radiating the heat off. The housing tends to be slightly cooler than the probe.

CTRacing
April 17th, 2012, 18:40
I have a 94 with a 4.0

I checked several points on the head. All came up with about the same temp, but still reading under what the gauge said.

Pelican
April 17th, 2012, 19:44
My gauge was reading high. Replaced aftermarket sender (in the driver side rear of the head) with an OEM sender to correct the problem.

CTRacing
April 20th, 2012, 16:16
Well I've replaced the sender twice with OEM style and it still doesn't seem to be right.

Tim_MN
April 20th, 2012, 16:39
Cheap crappy OEM style parts from IdiotZone/Advance/O'Reilly's, or genuine Jeep parts ?

Is you IR gun calibrated and certified ?

O-Gauge Steamer
April 21st, 2012, 06:49
DO not waste your hard earned bucks on Sensors from BozoZone or, for that matter, other "cost effective" parts sources. Go to either NAPA or better still, the Dealership. By the time you actually find a working sensor from the cheap outfits, you have more than paid full list price from the Dealer.

I have a friend, here in the Springs, that purchased an Oil Pressure Sender for his 97 from the local O'Really?. He instantly had wonderful oil pressure. Idled, hot at better than 40psig. Ran up to near 70psig when driving. I suggested that the part they sold him is an incorrect one... He has since replaced, with a Dealer sourced part, it and the gauge reads where it should.

FYI on the Dash Gauges. In the case of my 98, the PCM and the Dash both agree with an IR thermometer. One of the things I verified when chasing my "ultimate cooling system" was the "is the Jeep accurate" question. At least on mine, it is.

How very strange. Mostly, factory dashes are "For Reference Only" in nature.

CTRacing
April 22nd, 2012, 19:56
I have been buying the sensor from Auto Zone. I'll pick one up from the dealer and post the results.

Thanks for all the help!

hubs97xj
April 22nd, 2012, 20:31
DO not waste your hard earned bucks on Sensors from BozoZone or, for that matter, other "cost effective" parts sources. Go to either NAPA or better still, the Dealership. By the time you actually find a working sensor from the cheap outfits, you have more than paid full list price from the Dealer.

I have a friend, here in the Springs, that purchased an Oil Pressure Sender for his 97 from the local O'Really?. He instantly had wonderful oil pressure. Idled, hot at better than 40psig. Ran up to near 70psig when driving. I suggested that the part they sold him is an incorrect one... He has since replaced, with a Dealer sourced part, it and the gauge reads where it should.

FYI on the Dash Gauges. In the case of my 98, the PCM and the Dash both agree with an IR thermometer. One of the things I verified when chasing my "ultimate cooling system" was the "is the Jeep accurate" question. At least on mine, it is.

How very strange. Mostly, factory dashes are "For Reference Only" in nature.

The 97+ dash gauge is driven by the PCM, so the PCM and gauge will always agree.

I will agree with the advice to buy anything but cheap parts store sensors/senders. I'm 1 for 3 on aftermarket sensors in the last 2 years...

O-Gauge Steamer
April 23rd, 2012, 07:15
^^ Yes, the PCM and the dash should agree as there is only one sensor and the PCM sends the data to the cluster to display. Does not mean the factory sensor is accurate which is why I verified the actual temperature with the IR gun. Not surprisingly, there are temperature differences across the head. If you will, hot spots. Nothing drastic and once the engine has had time to soak, most of them average out.

It is my opinion that if you are going to chase a problem, you need to verify the data set with which you are working. Saves time in the long run.

CTRacing
April 23rd, 2012, 20:10
So bought a sensor from Napa and put it in tonight and.....it works! Stupid Auto Zone parts. What else do I need to not buy from them? Or should I avoid Auto Zone like the plague?

Tim_MN
April 24th, 2012, 00:28
Buy NAPA or genuine Jeep, especially for sensors.

Cheap crappy "lifetime warranty" parts are cheap for a reason.