17 Jeep wrangler 2 temp gauges, which is which

[another Todd]

My 17 Jeep Wrangler 3.6 has a normal 2" round gauge for temperature and runs straight up in the middle or within 1/16 of the middle at all times after it warms up. The other temperature gauge is digital and is located in the dash "information screen", this one, after warm up, is constantly fluctuating between about 200 and 226 but has gone as high as 232. It constantly goes back and forth between the two. Once it hits 200 it takes about 40 seconds to hit the high number of 226-230 then start dropping again to 200 then repeats. The radiator fan cycles higher and lower speeds but not in correlation with the temperature swings or even the AC mode. The engine does not overheat (boil over), but it does always smell "hot"
Is digital gauge oil temperature? Why the constant swings and never stabilizing even when highway cruising.

 

[crashz]

Typically, dash gauges are damped so that you don't see a constant change. Apparently this was a big deal to consumers long ago as they would see wild swings in temp and oil pressure and bring their cars into the dealerships for no reason. The manufactures have been doing it since. Essentially idiot gauges. For your specific Jeep, I'm not sure what the digital gauge is telling you, but I imagine if it was oil temp, it would display that specifically. That temp range seems like it should be water temp in the engine, but oil temps can also swing.

The swings are related to fuel burn rates, engine load, air flow through the radiator (either car speed, fan speed or both), cabin heating, outside temps, and thermostat cycling.

 

[MParr]

That sounds like coolant temperature.
I would suggest consulting the owners manual. They can be found online.

 

[jadmt]

My 17 Jeep Wrangler 3.6 has a normal 2" round gauge for temperature and runs straight up in the middle or within 1/16 of the middle at all times after it warms up. The other temperature gauge is digital and is located in the dash "information screen", this one, after warm up, is constantly fluctuating between about 200 and 226 but has gone as high as 232. It constantly goes back and forth between the two. Once it hits 200 it takes about 40 seconds to hit the high number of 226-230 then start dropping again to 200 then repeats. The radiator fan cycles higher and lower speeds but not in correlation with the temperature swings or even the AC mode. The engine does not overheat (boil over), but it does always smell "hot"
Is digital gauge oil temperature? Why the constant swings and never stabilizing even when highway cruising.

totally normal...the t stat opens and closes. when it opens the temp on the digital drops and cycle starts over.....I have had 4 wrangler JK's with 3.6 and a jl wrangler with 3.6 and that is normal...if you want to get freaked out toggle to the transmission temp and then put your jeep in park and watch the temp rise to match the coolant temp...put in drive and back down it goes.....

 

[another Todd]

That sounds like coolant temperature.
I would suggest consulting the owners manual. They can be found online.

owners manual doesn't state whether it is oil or water temp, just engine temp.

 

[MParr]

owners manual doesn't state whether it is oil or water temp, just engine temp.

It's coolant temp.

 

[another Todd]

totally normal...the t stat opens and closes. when it opens the temp on the digital drops and cycle starts over.....I have had 4 wrangler JK's with 3.6 and a jl wrangler with 3.6 and that is normal...if you want to get freaked out toggle to the transmission temp and then put your jeep in park and watch the temp rise to match the coolant temp...put in drive and back down it goes.....

The transmission temps are fine, but 230 water temp is substantially higher than I am comfortable with.

 

[D60]

AFAIC the fan is controlled based off engine load (which is a PID) and not coolant temp. I'm sure there is a water temp threshold that triggers the fan as a failsafe.

My JL won't run the fan if I keep the RPMs up crawling in 4lo, but if I try to run an even slightly higher gear (which is not unreasonable with the Rubi's 4:1) it runs the fan like crazy. Water temp seems to have nothing to do with it.

I've never heard anyone confirm my theory but I'm 99% certain I'm correct based upon real world experience.

 

[another Todd]

Just for fun, I am going to drop a 180 degree thermostat in it and see what it does. I have a new stock one waiting if the 180 doesn't go well.

 

[BC1]

Sounds like a fun experiment. I will guess the results will be worse economy, low coolant temp codes, fouled plugs, milky oil and burnt cats.

 

[meep]

Just for fun, I am going to drop a 180 degree thermostat in it and see what it does. I have a new stock one waiting if the 180 doesn't go well.

I wouldn’t. All the lower t-stat does is open up sooner, but it doesn’t give you more /cooling capacity/. In fact, it will likely increase the fluctuation because the fans still won’t come on until their normal programming, so the lower stat just introduces a wider range. Let ‘er reach op temp, she can handle it. For more capacity, youll need a larger radiator. For more clamped down stability, you can reprogram the fans to kick in sooner, or for more capacity change to a mechanical, really.

E-fans are great for fuel management, and especially in an off-road vehicle the ability to disable them if crawling through water. Arguably, they do better for cooling and AC in traffic. What we lose is top-end CFM when we are hitting it hard, towing a load, etc.

Also, it is entirely normal to fluctuate 30F in an old school, thermostat and belt-fan system. TOTALLY normal. Mash the throttle, they make heat.

 

[D60]

I put a true mechanical water temp gauge in a brick nose Ford and absolutely loved that thing. You could very clearly see the t-stat open at 195. The capillary setup is true, honest immediate response and won't lie to you. I just had a cheap Sunpro from AutoZone and it seemed dead accurate with the thermostat rating.