So is the mishimoto t-stat better then the ford OEM one? And what temp is the Mishimoto
T-stat? I'm replacing my sons and was going to go with the Ford OEM.

 

Ok team - thank you all for the input today. Here's an update. Brian asked me to check to EOT and ECT cold temp this morning. They were 83/84 - so they appear to be reading the same at cold soak. For the defueling conversation from high EOT, I don't know what that would feel like at this point. It didn't seem to change performance as the temp increased - the highest I saw it go was 262 if I remember correctly. Based on the cold soak results, I didn't get two new sensors today but I may should have. I DID pick up a new factory thermostat that I won't be able to put in till this weekend. My son is driving the truck about 7 miles to work and he doesn't see any of these issues under that condition. So I'm going to let him keep using it till I get back in town later this week.

I am craving a validation of the real ECT. I may look into a way to get another temp probe into the system somewhere. It kills me not to really know the coolant temp and not knowing which gauge to trust, if any!

 

Mishi sells a 185 and a 200. Its expensive. OEM is fine too I guess. I had a cheap aftermarket and it lasted about 9 months before staring to open too soon. It didn't open far enough when hit and started opening around 160 before I decided to replace it.

My first 185 Mishi opened at 196. They replaced it (lifetime warranty) and the second one is fine.

 

So let's see if I have this right
Your cold soak numbers ECT and EOT are with 1-3* each other
Your ECT jumps around not reporting steady

Your EOT is steady but high even pushing over 253* at times
New oil cooler recently trying to solve the high EOT but no change

 

Cold soak - yes. 1 degree diff.
ECT on dash is steady but then appears to go hot really quick while pulling. After ding ding on dash, temp gauge rises to the max over about 5 seconds. Scan gauge shows steady at maybe 205. While watching the scan gauge, I could, occasionally, see it flash from 205 to 245 and back. It mostly stays at 205. Turn the key off and on causes the dash gauge to return to normal in the middle. Go down the road a little while and repeat.

EOT is not unsteady - just high.

 

and yes, recently changed the oil cooler.

 

Id try what Bryan said and swap ECT for EOT
maybe even give the harness wiggle test while someone watches the gauge


The High EOT could be the Bypass as already mentioned or a water pump not pushing enough flow

The SGII is reporting same as the dash gauge or there info comes from same place
The SGII is live data but has a 3-6 second refresh rate that's the reason you don't catch Both gauges jumping all the time


go into SGII user setting and set update rate to FAST




Your issue isn't too common but not unheard of either more folks have fixed it by changing the oil cooler bypass then those that had to do a Water pump & front cover from the posts Iv seen but I could have missed some posts No doubt

 

Third time... Switch the sensors and see of the eot does the same thing. Or buy one new sensor and install as the eot.

Verify your scan gauge settings

 

ok Bryan - I'll swap them

 

Ok team, changed the EOT & ECT & Thermostat (all Ford OEM parts). No difference in behavior. ECT 200, EOT 230 not towing in just a few miles up to road. Haven't had a chance to diagnose any further but plan to work on it Saturday. If you have any more thoughts, let me know.

Mark

 

See if this helps. This is from a 2003 6.0. Not mine

 

And this also

 

And this is the valve

 

Tideman's last post was a very warn oil cooler bypass valve. This particular one cause high eots. However, as posted early on, oil cooler bypass valve problems are rare.

I had higher than normal eots when towing. Changed my bypass valve (by changing the oil cooler cover) and installed a new oil cooler. Dropped my deltas from 11 to 5. My deltas werent high to begin with, but when I towed my eot hit 256. I was doing 80 mph for 100 miles in 98 degree heat. I made sure I was using synthetic oil. It can take there heart better.

Changing the valve and cooler dropped my eot to about 245 towing in the same conditions. The old oil cooler bypass valve wasn't in bad shape. I'll mail it to you of you want it. Just give me an address.

Changed Tstats and bypassed my kitty and my eot towing hardly gets above 220 now. I speculated my TStat wasn't opening enough. Could have been a clogged cat, but it was pretty clear.

The difference between my temps and yours is my ECTs were always around 215 while towing. Now they hover around 208 while towing.

I was almost sure it was your eot sensor. Diasappointed to see it's not. Check your scan gauge program to make sure it's correct for the eot.

 

Bryan, did you use a OEM T-stat or Mishimoto? And how much weight do you tow? Was thinking maybe 185 degree Mishimoto for my boy, he tows 16K.