I noticed that some parts stores loan/rent code readers, not sure if the rental ones are advanced enough to read live data. But they could plug one in to do a free code read at many stores, and you may be able to see that coolant temp.

 

1.7 mpg better after 1 tank of gas. Will obviously need to calculate again after a few more fill-ups. Stock fan/clutch absorbs about 12 hp from what I research...the electric I doubt takes 2, but still, this doesn't really translate into any seat-of-pants difference...about like adding a K&N filter; barely noticable, but noticable.

 

Just bought an ultragauge couple weeks ago. Temps hover between 194-206F. Installed 180F thermostat and saw no difference. I have a radiator that's had dexcool for nearly 10 years, so I bought a new one (not installed yet). The fan works great, but it will be impossible to isolate cooling efficiency with all the subsequent cooling mods. 14.9 average mpg around town.

 

Temps are a little on the high side. I'm running a stock cooling system minus a 180 warm weather stat and I never see anything over 197. I consistently run between 188.6 - 194.0 on a 4.0 liter w/ 179,000 miles.

Your 206 temp seems high. Your radiator or heater core may be slugged up. You sure all air has been burped out after t-stat exchange?

 

You can eval your existing radiator. Warmed up, triuck off, measure temp top to bottom on fins. More than 10F spread means lower rows are blocked.

 

I had good results doing just that on my Jeep. The adjustment allows for fine tuning, and there is an override switch that allows you to turn the fan on manually if necessary. Key is to know exactly what the temp is, in the Jeep I had installed a coolant temp gauge, in my Disco I have an UltraGauge. Haven't done the electric fan swap yet, but I may! Only down side to the conversion is the controller. I had one fail on the Jeep not more than a year after I installed it, causing catastrophic failure of the radiator (the plastic tank split, and guysered 250+ degree coolant). Replaced radiator with aluminum, and now (after selling the Jeep) the new owner reports it overheated idling on the driveway! He just removed the controller and runs the fan manually!

 

Not a bad idea. May even add life to the water pump. I've thought about doing this, but never researched it. I may end up trying out this one along with the inline coolant attachment to hook the temp sensor to. All for under $100.
16" Electric Fan 3000 CFM Wiring Install Kit Complete Thermostat 50 Amp Relay | eBay
32 MM or 1 1/4 Inch Water Sender Attachment

 

Not 100% sure, no. Think I'll put the front end on ramps and reaccomplish. I hear that works better/faster. Also, I've not measured the temp of the fins top to bottom yet. Just assuming that after nearly 10 years of running DexCool, it's probably not good but I'll measure anyway. Don't mind hanging on to my new radiator for a few years if the one on there is good.

Can the heater core be flushed if there's build up in there?

 

I've heard the old Mark VIII and 3.8 taurus fans are the best. 2 speed (2500/4000cfm). You can pick one up with a shroud at a junk yard for about $20. Then get a wiring kit elsewhere or make one. This will be my next project. If even 1mpg is gained that is huge considering it would be a 10% increase for me. Thanks OP for sharing. I've been griping about my mpg for awhile and completely forgot about this.

 

I've really been considering doing an electric fan swap too, but the controller failure is the main thing that has me concerned. Would it hurt anything to just have the fan wired to come on when the vehicle is running, or does someone know of a reliable controller?

Not trying to thread jack just thought it seemed like a suitable place to mention it.