I'd appreciate any helpful advice, I'm getting frustrated.

This is a 2003 6.0 which to the ear, and to drive it is running great. No black smoke, no white smoke, no puking, no coolant loss, no white stuff around the degas bottle. I keep it well maintained. I've been chasing this problem for about a year now (well, actually kind of thinking about it, ignoring it, and not driving it a lot). Ex now has 116,000 miles on it. For the record, I'm about to send the FICM to ed, as FICM main voltage is occasionally dropping to around 46 volts. I'm also going to replace the alternator at the same time, as my original can't seem to bring the battery up past 12.2 volts. I also have a dashboss.

SO... the problem: Now that I have just replaced the thermostat with an OEM one (I have a Mishmoto and have been following that thread, but don't want to complicate this situation), the ECT seems to run around 192*-194* around town, and pretty consistently. My delta is really good, and normally EOT is not more than 2-4 degrees above that. Pulling grades (empty and not towing) is the problem. Pulling a 7% grade near my house for about 2 miles, at 85* outside temperature I see my ECT climb to 202* - 205*, but then drop right back down when I flatten out. Other than that it seems to mostly run in the 192*-194* range. In the above case even, it seems to only really begin to heat up in the second half of the two mile grade. I know from a trip I took last year, with no tow, and very little extra weight on board that on long grades in higher temperatures it will climb closer to 220*. Okay, so head gasket? Water pump? Fan? As far as the fan goes, how can I test it? Even pulling the above mentioned hill last night the fan duty cycle always said 0%... never went above that. The fan speed was always 450-500. Also, I've heard many posts where some of you have described hearing the fan come on and that it sounds something like a jet engine firing up. Neither my wife nor myself can recall ever hearing that, but maybe we just weren't paying attention.

Sorry for the long post, thanks for any help!

Mike

 

hopefully some one else when chime in, but sounds like you need a fan clutch.
is your EGR valve in place and plugged in? if not, it will not allow the fan to operate like it should.
the duty cycle should not always be 0
and you should see more than 500 fan RPMs with an ECT of 220*

 

Do you have any codes for the fan ? Electric variable I think .

 

Yea, the fan clutch is definitely suspicious. I wish it were cheaper to replace, I'd just change it out to find out. EGR valve is still in place, and I religiously pull and clean it about every 10000 miles. Lastly, the 450-500 fan rpms was yesterday where it only climbed to the 202*-205* range. The trip where it was up to around 220 once or twice was a year ago, and I do not remember what the fan speed and duty cycle were doing then.

 

Not throwing any codes, and didn't last year on the long trip where it got hot going up long grades.

 

IIRC there was another post where someone bought the fan clutch from a local parts store, and it seemed to be the exact same part with matching numbers that you would get from the dealer. i am pretty sure it was less than $200, were as the ford part was $400+

 

Apples and oranges , But I just put on on a ram . No codes with it . Only complaint was AC performance . Data showed low fan speed . A new fan clutch solved his issue .
Not sure , but yours may be the same . Bad but no codes because there is no electrical fault .

 

Yea John that is kind of what I am wondering about... something like that. Interestingly enough, I just went out to the driveway and ran it for a few minutes, got it up to 160* ECT at 93* outside temperature. I reved it up to 2000 rpm and held it there for a minute or two. Fan duty cycle hovered in the 48-52 percent range, and the fan speed ran about 800-850 RPM.

Any chance this could be something like a broken water pump impeller, or a hole in the baffle behind the water pump... Just think out loud.

 

Anything is possible , But , I have not seen impeller issues on those water pumps .
If you are at 2000 rpm and only see 800 out of the fan , Get it up to full temp and see what it shows . Sounding like a bad fan clutch . Full temp , full duty cycle , fan speed should be higher .

 

Okay, so I just went out and ran it up to 192* ECT, at 93* outside temperature. @2000 RPM I got a fan speed of around 1050 to 1100 rpm, and a fan duty cycle of about 52% - 55%.

And the thing that I don't understand is why yesterday, climbing that short grade, with temperatures suddenly going from 192* up to 203* or so, did the fan duty cycle read 0% the entire time.

 

Do you have the Auto A/C head in your 03?

 

If you mean the control head inside the cab having Auto A/C, then yes.

I'm interested to know where you are going with this.

 

As am I .
Willing to learn . Eager for knowledge .
I never claim to know all .

 

Have you checked between the condenser, radiator, and CAC for grass, etc, just to make sure it's good and clean?

 

Yes, and cleaned well when this first started happening.