sigmanf150

Hey guys.

I'm running an electric fan conversion on my 04 SCAB 5.4 yet I'm having some trouble (or maybe worried) with the CHT reading vs the ECT reading on my ScanGauge II.



This picture was taken while I was towing my 31 foot 6500lb camper up a big hill on the highway @ 65mph. Tranny temp is right where it should be. It floats within 10 degrees or so all the time while up to temp and towing so I know it's right. However, the CHT and Water temp are what concerns me. I understand that the CHT is what the PCM sees and then it determines what the coolant temp is from that reading. By looking at just the coolant temp reading pulling the camper up a hill going 65mph I only ever hit 211-213 tops, and then it drops quickly when I level out. That should be normal and I expect that when I'm towing a heavy load. Also if I pull over to the side of the road and whip out my laser thermometer and point it right where the CHT resides or at the thermostat housing it will show 211 and falling, usually matching within 4 degrees of the ECT reading on the scangauge, but eventually settles back around 188-191 when idling for a minute or two. The CHT reading always seems to be up to 40-50 degrees higher than the coolant reading. As you can see in the picture, the truck is 2 degrees away from shutting down half of the fuel injectors according to the following script from my allDATAdiy account:

"The cylinder head temperature (CHT) sensor:

is mounted into the wall of the cylinder head and is not connected to any coolant passages.
sends a signal to the PCM indicating the cylinder head temperature.
if the temperature exceeds 126°C (258°F) 5.4L, 130°C (265°F) 4.6L, the PCM disables four fuel injectors at a time. The PCM will alternate which four injectors are disabled every 32 engine cycles. The four cylinders that are not being fuel injected act as air pumps to aid in cooling the engine.
if the temperature exceeds 154 °C (310°F) 5.4L, 166°C (330°F) 4.6L, the PCM disables all of the fuel injectors until the engine temperature drops below 153°C (308°F) 4.6L, 154°C (310°F) 5.4L.
DTCs are set.
If the engine reaches critical temperature, the following happens:
The coolant temperature gauge pointer will read fully hot at 121°C (250°F). The check gauge warning indicator will illuminate."


The temp gauge on the cluster doesn't seem to respond to the changes in coolant temp, but as I've been able to surmise so far, my coolant temps are right where they are supposed to be. During stop and go traffic even while towing the camper, my temps stay between 188 - 195. They only rise when I'm accelerating on an on ramp or when I'm trying to maintain my speed on hills. It drops while exiting the freeway on off ramps. The new 18" 4000cfm electric fan pulls the temps down very quickly once I'm off the freeway. City driving is no problem at all. It's only on the highway where temps seem to rise. Again, I do not get any warning lights on the dash and the temp gauge stays pretty much dead center between C and H. No codes are stored in the computer either.

So, what's going on? I understand that having a ScanGauge or Edge or whatever showing you a live digital readout of what are normal temp fluctuations can create a lot of premature anxiety and the only way to cure the worry is to stop reading the digital readouts! But for me and my issue, I just need to know that the CHT readings I'm experiencing are either normal or not. I've looked everywhere and can't seem to pinpoint anything that states what the differential calculations are that ford's PCM uses to calculate ECTs from CHTs and how far the two readings should be apart. Maybe the problem could be with my ScanGauge?

I dunno, but I need help! I'm fixing to order a new CHT and cross my fingers that the existing one is reading too high because it's old or something. BTW, I have already changed the coolant several weeks ago and flushed it the best I could without having one of those Prestone flush kits (I will be buying one tomorrow). The old stuff came out cloudy and brown, so I've also just purchased a new motorcraft water pump in anticipation that the fins on the old one are rusty. I've also verified the thermostat opens and closes properly.

Please help!

06_F150

I have the scan gauge but have only been looking at the calculated coolant temp. I have the 2010 motor craft Efan with two controllers. The first fan starts at 60% at around 193 and ramps to full at 203. The second fan is set slightly higher. I usually see 188-191 most of the time and the fan hardly ever comes on but I have not had this setup in the summer. Last weekend I towed a F100 to a car show. I think on the highway the highest we saw was around 196.

Are you sure the fail safe temp refers to CHT and not FWT? I have the OEM shop manual I will see what it says.

06_F150

Also the cluster gauge is not linear. It will stay in the middle for a certain range and go to H if the PCM thinks the engine is hot. I don't know the boundary temp but I will take a look at the service manual.

sigmanf150

I am interested to hear what the OEM shop manual says...

I just want to make sure I'm not burning anything up or I'm just being too worried.

rubbinsracin

I dont have electric fans, but as an OEM baseline I was towing my 28' enclosed with my racecar and full load yesterday at 70mph with an ambient temp of about 85* (atleast thats what the bank sign and dash readout said) for my races tomorrow night and my Torque app on my phone was telling me that the coolant temp was about 205 while running down the highway.

sigmanf150

UPDATE: I installed the Prestone flush kit and completely flushed out the coolant system this time. I also installed a 180 degree stat and a new upper rad hose. Used the Heater hose flush T to remove any air from the system and filled with fresh coolant/water mix.

Truck seems to run cooler now. I'll be towing my camper next weekend so I'll see if it really helped!

jamie930

old coolant will not remove the heat as well

sigmanf150

MAJOR UPDATE:

K so I figured I would try to install a new CHT sensor, but to do so you have to remove the intake manifold among many other things. I started tearing it down and soon after a thought popped into my head. " how do I really know if my ScanGauge is telling the truth?"

So I hooked up the Ford IDS VCMII Programmer to the truck, and OMG, the scangauge was wrong! Normal idling at full temp is 188-192 on the CHT temp according to IDS, which is 2-4 above the inferred Water temp, which is spot on. So It turns out I need to send my scangauge in for recallibration and updates!

Thanks to all that helped!

06_F150

Glad you got it sorted. I have had some issues with the beater machine the service manual is on. One thing I found under the test procedure for the fan clutch Is that the fan clutch doesn't fully engage until the air temp in front of the clutch is 205. The stock thermostat is 192 I think with the 180 you might have trouble getting to temp in the winter. Did you program in CHT as an xgauge? It is not listed as a default on mine.

sigmanf150

When winter comes around I plan on swapping back in the stock 192. Yes I had programmed the CHT as an XGauge. Go on to scangauge's website under xguage and you can see the coding for the CHT.

I would be extreemly interested in seeing if you have the same problem as I did. If you get a chance to program yours, let me know!!