One of the biggest topics of discussion is coolant temperature. What is discussed much less is the accuracy of sensors. He is some food for thought...

On my P38 (essentially the same engine as the D2) I found an ENORMOUS difference between a Land Rover branded temp sensor and one that arrived in an 'All - Makes' brand package.

The genuine sensor consistently produced an OBD reading 3-7 degrees below what my infra-red thermometer suggested. I was taking the reading on metal tube out of the plenum prior to the rubber hose and the metal tube between the thermostat into the heater core.

The All Makes produced an OBD reading 20 degrees hotter than the same infra-red readings.

All this is to say that the quality and accuracy of temp sensors can be HIGHLY variable. Before embarking on a mission to lower your temps, verify with an inexpensive infra red thermometer first.

 

Good advice, I carry one of these in all my trucks: Also good to not depend on the obd2 temp gauge.

 

Last year I got a new temperature sensor to refresh a P38 engine to be dropped into my D2 and it was off several degrees C (lower). Instead I decided to reuse the 20 year old temperature sensor that came with the D2 engine and it is a off only 1-2 degrees C (lower). I can measure the block temperature with a digital temperature sensor (+-0.25 deg C), which I added to the block just next to the factory one (I deleted the TB heater and used the coolant output for the sensor).

 

Tim, why are you saying not to depend on the OBD2 Temp. gauge? I use my Ultra Gage to give me the coolant temp. I can see the difference when idling. pulling a trailer etc.
I'm following this discussion as for a long time - my Ultra Guage temps. were always consistence 178F once fully warmed up, or so until one day, I turned off the Disco and then 3 hours later, back on. Now my Ultra Gauge will display temps from 167F 169, 173, etc. up until about 179 and then drop down again to around 167F. This "swing" in temps happens withing 60 seconds or so. I've unplugged my Ultra Gauge, disconnected the battery etc., no change, still the "swing" in temp displayed on the Ultra Gauge. Been thinking that it must be the OEM sending unit, but I haven't had a chance to spend any time researching. Open to any comments/suggestions. Thx. Gregg

 

Guessing Tim was referring to a trust but verify type mindset. Especially given the OP posted about inconsistencies within the sensors, which are feeding the OBD2 readings.

 

Yes, I have had bad sensors before as have others, which is why I carry and IR gauge and run mechanical gauges on my rigs. The OEM sensor probably has an accuracy +/- 5%, which can be as much as 10 degrees and when they fail it goes beyond that.

 

Extinct,
what mechanical sensor do you recommend?

 

I run a dual electric fan on my personal rig (kit coming later next month, along with single and dual gauge pods) so I run a Davies, Craig EWP fan control module that has a built in gauge https://daviescraig.com/blog/davies-...BoCD5IQAvD_BwE However before that I liked to run the Innovate Motorsports MTX-D 3913 dual oil pressure and temperature gauge because of the programmable alarm capability. The gauge is supposed to be for oil temperature but the sensor works equally well for water temperature.