So first, a bit of history...

Truck: 2000 V10 4x4 Limited, stock engine/exhaust except the SCT tuner.

Last summer I was pulling our 7500lb S&R trailer (from Chico to Sacramento - flat roads)...it was in the high 90s...about 5 miles from Sac the engine kicks into limp mode, temp was pegged, SEL came on (code was cylinder head overheat - can't remember which one). Pulled over, swapped the trailer to another rig, and limped it home. I suspect I lost my fan clutch. Replaced the thermostat, fan clutch, water pump. A few days later, the radiator springs a leak...replaced that as well. Truck ran fine but I was only towing on the flats.

I have an SCT and the coolant temps run about 202 on average...only once in a while to I hear the fan clutch engage. When the first issue happened I had the SCT programmed with the 87 power tune.

On Thursday I pulled a different trailer (again around 7500lb) from Sacramento to Portland, still with the 87 power tune. My eyes spent more time on the coolant temp than on the road. Temps were in the 60s in the AM, high 70s/low 80s in the evening. On multiple long inclines, I would get a temp warning light and the gauge would peg, but the SCT would be reading 208, 210. No SEL light.

I was able to make the run (although I grew a few more grey hairs on the longer inclines)...I'd run in normal drive until I hit around 60, then I'd kick off the OD...then if I dropped below 45-50 I'd drop it into D2.

I noticed at higher RPMs I'd see the coolant temp drop (but of course the oil temp rise). More water = more cooling...but still I rarely heard the fan kick in...usually around 208-210, but one peak at 214 and I still didn't have the fan clutch kick in.

On my way back, it was light rain and temps in the high 40s. Put the SCT into 87 tow. No warning lights on the way home, but temps still maxed at 214, fan rarely kicking in. It went down to 38 degrees intake air temp at one point (rain/sleet/snow mix) near Mt. Shasta, temps there were down to 198 on the downhill grades, 208-210 on the uphill grades.

On the Sacramento Valley floor temps averaged 208-210 (had some headwind) but intake air temps were in the high 60s/low 70s.

I'm feeling like something is still wrong with the cooling system. I'm not sure when the fan should be kicking in, but I think it's barely doing it's job. If the fan IS kicking in at the correct temps, I have no idea what else could be wrong (considering a new thermostat, new fan clutch, new pump, new radiator).

Question 1: How can the coolant warning light/gauge kick in at one temp on the way up and not at that same temp on the way back? Are there multiple coolant sensors on the motor?
Question 2: What temp should the light be kicking on at?
Question 3: Around what temp should I hear the fan kick in? I know it's hydraulic, but I would think they would be around the same temp from one to another.

Any ideas? I'm wondering if I should just find a non-clutch fan and let it run all the time, but I don't know if they even make them for our motor.

On a side note (and unrelated I think)...I had an oil pressure sensor go out on me recently (after the cooling system died but before this trip to Oregon). I had oil all around the sensor back to the exhaust crossover and you could smell the oil burning on the exhaust pipe.

I replaced it and immediately had that one start leaking (but far less). Took it to a shop and they said it was a cheap sensor. They put in a Motorcraft and it was fine, but they did say they think I have either an oil pan gasket leak or a main shaft seal leak...they put in dye to the oil so they can look at it again. Underside looks like a class 1 leak, however I do occasionally smell oil on the exhaust after a hard run. No drops on the ground.

I doubt the oil is any relation to the cooling system issue but figured I'd put it out there. And for anyone wondering, the shop is quoting around 3k to replace the oil pan seal, and another $200 for the main shaft seal (might as well do that if the motor is halfway pulled out to do the oil pan gasket anyway). Sounds like robbery to me but I can't see any other way to get the oil pan off than to pull the motor up a few inches.

Any ideas folks? Appreciate any suggestions at all!

 

...anybody?

 

are you also tracking the CHT temps on the gauge like i do? Those i find to be much more useful than watching coolant temps.

I have a Torque Pro setup and i am able to track the coolant, Trans, and cylinder head temps all on screen.

1. You might have air trapped in the heads, park the truck on a strong incline is the easiest way, so that all the air heads to the front and ends up in the radiator, i had this problem on my 07 GT, temps were doing odd things, to i drove it up a dirt berm and e-braked it, and was able to pop the hood and burp a bunch of trapped air out of it that i never knew was there, on the Ex, jacking it up might not be an option, but if you have a 30ish degree incline somewhere such as a pile of dirt, or something, it might prove useful, but this is a guess, vacuum filling the cooling system would help eliminate this as a cause.

 

My 01 is RWD so I was able to use jack stands and a jack to get the front far enough up to burp when I replaced the radiator and flushed. If you dont have a berm you might be able to put the rear wheels in a ditch or depression and jack up the front.

 

I have a SCT, I -think- it has CHT as an option, I'll check it after class today. If it does, what temps am I looking to maintain? Is there an acceptable range?

I'll look at finding an incline also. The foothills are just a half hour away, I'm sure I can find something. Do I want to idle on the incline first, or just get it up and shut down the engine / let it cool / burp the housing at the thermostat?

 

...unfortunately the SCT doesn't have CHT as an option. I may have a scan tool that has that option...will check that tomorrow.

 

CHT on mine running temp is 225-235 at the running nice and cool side, such as doing 45-65 with no load just rolling with traffic and good wind across the radiator. I have seen it get to 260 which is my personal no go zone, that was when the intake pipe was missing the front piece so the intake was drinking air right off the radiator outlet and the exhaust manifolds, sitting still with zero airflow, and as soon as i started moving it dropped down into normal range. I am in arizona btw. Im an engineer, the way i figure it, the melting point of aluminum is 1221F, and it looses significant strength and rigidity around 1/4 of that temperature, so with an added safety net, i do not ever let it get over 260F, and i actually have my torque display setup now to do a visual and audible alarm if it gets to that point. It never goes up there even under heavy load or even WOT down the long onramp onto the freeway when im driving like a jack ***. It has only ever approached there while sitting still parked with no good airflow/wind, slowly just saturating itself, and with the intake pipe to the outside of the truck missing at the time.

Aluminum Temperature to Strength chart, by the time you get to 150"C = 302^F You have potentially lost a massive amount of strength in the material
Keeping the CHT temps between 212^F (100^C) and 240^F (115^C) is a realistic target that can be maintained, and means you retain almost full strength in the materials, meaning no warped heads, cracking from heat stress, etc....



Coolant temp averages between 185-220, usually on the lower side, unless again im sitting parked for a long time, with the ACs full power etc. but even then, since i have fixed that pipe, and closed the two little holes on the side of the filter housing, it has not built up temps as fast as it used to, those made a big difference in its heat buildup when sitting.

Note that i have a 180F thermostat also, which helps get it open sooner and keep the CHT temps down lower. Lots of people dont understand that the Heads can actually be hotter than the coolant is and by the time the coolant gets to the point it opens the factory thermostat fully, the heads are actually surpassing the coolant temp by about 25-35 degrees, at least here in arizona that is. So by getting the thermostat open sooner, at lower temp, the CHT has actually stayed lower as well. Again i believe that may be different if your not in a super heated climate, here in arizona its a winning combo.

The above chart and temperature information is from reference of Michael LaRosa, B.S. Metallurgical and Materials Engineering & Economics, Case Western Reserve University

 

I didnt have to open anything up. I saw some small bubbles after jacking it up but wasnt until after cranking and running it that I saw some big ones come through. Ran speed up and down a few times to get good flow. No issues since. Have pulled my 9k TT all over the Carolina's in winter and summer with no temp issues. I do have to add I'm just looking at the idiot gauge though.

 

Cocky EX, thx for that, I'll try that this weekend.