Wonkie Coolant Temp

Understandable. At some point, wouldn’t it sense the hot coolant?

 

Makes sense. I still wonder then why it actually works sometimes. I do think my ignorance is clouding my thoughts. I’m stuck on it working part of the time, and when it does work, it works great. I can watch the gauge climb until 195ish then stop.

 

I have this

 

That certainly can happen, but usually only after a coolant drain/refill, in my experience. Normally it resolves after a few cycles.

Another remote possibility is gas pockets from a head gasket leak. A sniffer tool at the radiator cap may reveal that if so.

 

might be worth pulling the sensor and testing it with a multimeter (OHMs) in boiling water.

I had a brand new sensor and gauge (new Stewart Werner) earlier this year that was giving me really off readings. SW sent me a chart that detailed what the readings should fall between. I gave them the OHM readings that I got from testing the sensor and they told me that the wrong sensor had been sent to me. It wasn't faulty, it was just the wrong sensor.

Might also be worth checking the wiring, making sure the connections are secure and clean. could do an OHM test on the wires/connections too. The wiring itself should have very low readings.

 

What brand gauge are you using? It’s not unusual to have a “bad” gauge giving unreliable readings… particularly cheaper gauges. Did your aftermarket gauge come with the usual set of thread adapters?

 

Look at the picture of the new gauge sensor. You can not ohm out a mechanical gauge. There are no electrical connection. A boiling water test would be good though.

 

ah, my jeeps have always had electric gauges, I guess they had all been replaced at some point prior to me owning them.

 

I too like mechanical gauges but at times they can cause issues such as what you are experiencing. First, I do not know the water flow characteristics of your intake manifold but, I suspect it is different where you placed the new gauge's sensor versus the factory sensor's location. I have seen your type of issue before. I believe water flow and air entrapment are causing your odd gauge readings. Danielbuck noted his jeep always had electric gauges and that is what your jeep originally came with. If you want to correct your odd temperature reading, I suggest you remove the mechanical gauge and plug the port in the manifold. Purchase a good quality electric (SW, Autometer, ect.) gauge and appropriate sensor for the gauge. Install the new sensor in the factory sensor location and wire it up.

 

Well, an interesting development. I installed a coolant recovery bottle, and, voila…gauge works 100% of the time. Before this, i had the coolant level a couple inches below the top of the radiator, now, at the top. Seem reasonable?

 

I would just monitor the overall content level for an extended time, be sure there is no head gasket leak or whatever causing the vapor bubble.

 

I thought that maybe because it was in a different place, it could happen