I have a 2003 6.0 Exc. I have installed an external "Bullet Proof" oil cooler, and essentially all of the "bullet proofing" accessories with the exception of head studs. I also have installed a Mishimoto oil cooler, as the OEM cooler had a crack in the upper tank, My particular problem is that the cooling fan does not kick on(audibly) until about 230 deg or so. It quickly cools to about 215, and the fan kicks off (audibly). On the long uphills here in AZ, it will repeat this process, sometimes getting as high as 240deg. (as monitored by my EDGE tuner) I have utilized the blue-wire-to-ground trick noted elsewhere, manually turning the fan on myself, and that works great. What I'm asking, is what sensor sends coolant temp to the ECU, ( and where is it located in the cooling system) which in turn determines how much to turn the cooling fan on? Any idea what typical level the sensor sends to the ECU to control the fan? I would like to put together a circuit that "fools" the ECU into turning the fan full "on" at about 210 deg, and stays on until the coolant temp reaches 195 or so. I would like to check that sensor first, and make sure it is working correctly before I try to band aid a fix. Any thoughts..?

 

Still have the EGR valve plugged in or not?
You want it plugged in even if you just zip
tie it somewhere. Has something to do with
cooling fan operation.

 

Interested in your answer on the EGR valve.

Did you mean to say you have two oil coolers? Or did you mean to say Mishimoto radiator?

Are you towing when you get this hot?

Does the oil temp come down quickly at idle?

When experiencing these elevated coolant temps, what are your oil temps doing?

Have you verified that the sensors all read the same after the engine is fully cooled down (a good 10 hours of "cold soak")? Check EOT, ECT, TFT, IAT1 and IAT2 at cold soak (and tell us what the ambient temp is).

Actually, you might as well just report on all the temps when the coolant temp is that hot (EOT, ECT, TFT, IAT1, IAT2, ambient). Report these when driving and experiencing the high coolant temp.

fyi:

Engine temperature is not the only parameter that the PCM monitors to determine cooling fan operation. The operation/description of the FSS (Fan Speed Sensor) from the PC/ED manual has a fairly good explanation as to how the system "thinks". This is not your traditional engine hits temp X and the fan clutch locks up. The fan speed sensor is a Hall-Effect sensor integral to the vistronic drive fan (VDF). The powertrain control module (PCM) will monitor sensor inputs and control the VDF speed based upon engine coolant temperature (ECT), engine oil temperature (EOT),transmission fluid temperature (TFT) and intake air temperature (IAT) requirements. Also, the air conditioner high side pressure switch will cause the fan high speed to activate (ACP V). When an increase in fan speed for vehicle cooling is requested, the PCM will monitor the FSS signal and output the required pulse width modulated (PWM) signal to a fluid port valve within the VDF. At least one person has seen the factory gauge go from normal to the "red" quickly. It happens around 240 degrees F.

Have you pulled your IAT2 sensor and inspected (or at least monitored it)? If heavily fouled, it can suppress fan operation.

 

I wonder if mine is operating correctly as well. Does someone have the Fan troubleshooting section of the service manual they could post?

 

I got tired of running hot and did the 6.0 to 7.3 fan clutch swap and it dropped my ECT and EOT by about 10 degrees due to the fan clutch engaging earlier and running longer. I don't understand why they would put a fan on these that won't come on at speeds under 45 and only runs a few seconds. The temperature controlled '97 7.3 fan clutch is just so much better it's a no brainer. FYI- the 7.3 fan is not loud like most of these guys claim it is. It gives me peace of mind that my truck is being cooled like it should! My ECT was running about 205 with no trailer and 215 with one and now I run 194 without and about 205 towing in south Texas heat between 90 and 100 degrees air temps.

 

Neither of those things are true? The fan clutch will receive a full duty cycle command under 45mph, the fulyl duty cycle command will be for longer than a few seconds, and the clutch will be fully locked under 45 for longer than a few seconds.

You do you, I don't care if you want to run a mechanical fan clutch, but the statement you made is factually inaccurate. If yours was not operating correctly, that's a separate issue from the design of the system.

The procedure is basically a two-part WAG: minimum and maximum speed tests. Run the engine in a situation to not command the clutch, and verify fan speed is less than engine RPM at 3000rpm. Then run the engine is a manner to induced the PCM to command the clutch, and verify fan speed exceeds engine speed. Basically you stuff cardboard into the grille and run the engine at 3000RPM until ECT exceeds 205*f, which coupled with Max A?C should command a full clutch engagement. It's definitely not the best diagnostic section of the manual.

 

I guess mine was screwy...glad it's out of there because it wasn't doing it's job.

 

Where did you get your upgrade? BPD?

 

Adapter nut from BPD and 1995 7.3 Murray fan clutch from O'Reilly's for $90 shipped. Made in USA!

 

I couldn't rep you, but I like the "WAG" procedure.

 

So the nut and the clutch and the fan itself works with this? I've been thinking to do this on my sons.

 

My bad, meant Mishimoto replacement radiator

Towing exacerbates the problem. will run hot (220+) (outside temps 100+) empty on long grades in Az. Manually activating full pulse width on PCM fan control results in coolant temp drop of 10-12 deg in 3-4 minutes

Oil temp seems to lag coolant temp in rise, but cools quicker when PWM is full on.

Will note temps of other functions EOT, ECT, TFT, IAT1, IAT2, ambient next time I take it out on the road.

As a side benefit, the AC appears to work better (not documented) when the fan is "on" 100% duty cycle via the blue wire being pulled to ground.

 

Yessir and it works great, KISS principle! Keep It Simple, Stupid! No computer control, just a mechanical thermostat.

 

Do you get a light and a code when you did this? Like to know for smog here?

 

No and I also did a full EGR delete including the EGR valve. You can remove the EGR valve and not have cooling issues because your PCM is no longer controlling the fan operation. I could see a trouble code on Torquepro but no Check Engine Light.