Some of you may have seen my note in another thread, but I thought that I would kick it out here for some answers.

Starting off, I have a Bone Stock '06 6.0L FX4 CCSRW Short bed. A bit over a week ago I finally got an Edge Insight CTS2 to monitor and am in the process of selecting the PIDs.

I noticed a couple of things and after doing some searching here am wondering if my hunch is correct about a failing thermostat.

First off, the mileage has dropped a bit to about 13mpg. My daily commute is about 15 miles to and 9 to 15 miles home. Mornings have been in the low to mid 40's and no higher than 65 in the evenings. Watching the EOT and ECT, I have not gotten above 187 on EOT and 185 on ECT even when WOT getting on the freeway. I am trying to let the truck warm up about 5 min. before getting on the surface streets, and then it is usually between 1.5 and 5 miles before I get on the freeway.

Are my lower temps from the ambient temperatures or am I seeing the thermostat fail?

 

Sounds just like the last 3 Motorcraft thermostats I've had.

 

Mine has been the same as yours since its gotten cold here, similar temps to your outside temps.

 

How's it going Will, I think your ok , your 187 goes up after the 15 min drive , these trucks take awhile to get up to temp , mine does the same with the cool mornings, I usually wait till ECT hits 80s before I hit the high road.If in doubt ( probably more work than just installing a new OEM ) pull it and boil up a pan of water and dropper in , it should open at 180 deg

 

Isn't the OEM thermostat supposed to be 192°?

 

Yea typo, thanks for keeping me in line

 

That's what I thought and was seeing while shopping online. I've had two diesel mechanics locally say to stick with a stock one, but I'm considering a Mishimoto 200*. My only concern there is we will hit 110*+ ambient in the summer when I do most of my towing. Gotta love Northern California with our temperatures

BTW Torr, your signature applies here too.

 

I got some live data this morning, ambient temp was 44*F

KOEO. 1st picture

KOER. 4th picture

AFTER 10 minutes idling at stoplight. 2nd picture

After 15 minutes at 75mph. 3rd picture

I'll have to re caption these when I can get to something besides my phone.

 

Sons truck did fine with the IA heat and humidity this summer. Mishi has a tighter swing, so just because it opens 10 degree later does not equate to 10 degrees warmer on the topside.
My delta actually dropped a solid degree after I switched to a Mishi......I'm sure it's because the swing is tighter, and got a solid 1 mpg boost as well.

The 6.0 is much happier running a little warmer. You should be at least 10* higher than what you are running 75 mph

 

Modoc, your voltage in three last pic is 11.6v. Are your glow plugs still on?

 

Yes, that is Key On Engine Running immediately after start after Glow Plug Indicator turned off while warming up to 80* ECT

 

I bought my stock '06 back in January. Temperatures were eerily similar to yours.


Upper radiator hose failed and had to have shop replace it. They replaced the thermostat while in there (done at Ford house, presume MC thermostat).


ECT runs 190-195 unloaded, maybe 200 in heat of summer. Oil temperature is typically 8-15 degrees behind coolant temperature all the way up to the 195 ECT. It probably takes a good 10-15 minutes of city driving to get EOT to equal ECT.


I do think your thermostat is open too much. Had I known how well folks think of the Mishi I may have had it installed instead. Hindsight is 20/20.

 

I went through three Motorcraft Thermostats that couldn't maintain 190 degrees. So I went with the Mishimoto and haven't had a problem since.

 

My 2004 Excursion 6.0 only makes it to 178F. Mishimoto thermostat going in Saturday morning. That with an 80F outside temp. Maybe 185 when I stop for a while then back to 178 while moving.

 

I just installed a Mishi 200 thermostat on Tuesday and my temps have gone from 188 to 209. I only ordered the thermostat and did not get a new housing (RT1169) and I am wishing I would have because my housing was worn out and the thermostat did not sit flush so my thinking is it is holding it closed.

SO if you replace your thermostat GET A NEW HOUSING. Mine will be here today. I have been reading the 1000 page Mishi thread and wish I would have read just a few more pages and would have ordered the housing.