How hot is too hot?

[laserjock]

Alright. It’s been pretty well documented that I’ve been struggling with water temp issues on my truck to the point that I did this.

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I took my first trip today loaded down through the mountains and I think it was a mixed bag. I’ve got plenty of fuel now. Truck runs good. It just runs really hot. I finally have a good temp gauge so I can really see exactly where we are. I got nervous at 240. I saw 250 a couple times just for a minute or two.

My sender is in the stock location which is the hottest point. The interesting thing is I have my stock sender in the back of the passenger head. So really I’m watching the hottest point and some indication of water temp coming from the radiator. Even at 250, the factor gauge in the head was never out of the normal range. I still have the overtemp light sensor in the head and it never came on. I think it is supposed to trip at 260?

Anyway, I don’t like it that hot at all. It’s definitely not heat soaking the radiator. The big fan is currently on a motorcraft thermal clutch. It is definitely engaging I can hear the belts starting to squeal and as soon as I top the mountain it falls like a rock all the way back to 190. Most of the time it runs between 200 and 225.

So there’s a couple things here. The fan is not coming on soon enough. It’s not coming on until the gauge is reading 235 or more. That’s just too late. Damage has already been done at that point. I know it’s coming on now because the Vbelts start screaming for mercy. So there’s that little problem too.

So I guess the question how hot is too hot? Sustained vs short periods?

I think my next step is going to be fitting the 6.4 clutch so I can bring it in sooner. Slightly longer term may be going serp belts to turn this monster fan.

Welcome your thoughts on any/all of this.

 

[chris142]

I would NEVER let one get over 230. 250 is melt it territory

 

[ifrythings]

The over temperature sensor should kick on at 248f (120c) if it even works, I had 3-4 of them that never worked. Have you double checked your gauge to make sure it’s correct?

I really like the 6.4 fan clutch, it’s nice that you can tie in the AC, trans temp and intercooler and you can turn it on whenever you want.

 

[Cubey]

My RV usually usually runs at 210-220 at most with a new Motorcraft fan clutch and thermostat (installed late 2019), when climbing pretty steep grades. Normal flat highway is around 180-200 depending on speed, wind, ambient temperature. That's not bad for how big, tall, and heavy it is... plus towing a 5x8 fiberglass enclosed trailer.

 

[Laine D]

That is crazy. I have never seen over 225 on mine. How hot was it outside when you were running it?

 

[subway]

that seems a bit excessive for heat, a lot of guys would say that it is in the head gasket danger zone. I don't know what the true limits are with short bursts of heat vs sustained exposure. I suppose it starts getting down to the integrity of the engine and how well those bolts/studs clamp down.

you might be able to cheat in the mean time and bend the thermal spring in the front of the clutch to cause the fan to come on sooner.

have you considered running waterless coolant?

 

[pafixitman]

That sucks Mike. No real idea but could stacking the intercooler and ac in front be restricting air flow?

by the way, for Kyle Larson In the #5 on Sunday 315 was too hot....js

 

[Laine D]

That sucks Mike. No real idea but could stacking the intercooler and ac in front be restricting air flow?

by the way, for Kyle Larson In the #5 on Sunday 315 was too hot....js

He lived down the street from me and I had no idea

 

[chris142]

that seems a bit excessive for heat, a lot of guys would say that it is in the head gasket danger zone. I don't know what the true limits are with short bursts of heat vs sustained exposure. I suppose it starts getting down to the integrity of the engine and how well those bolts/studs clamp down.

you might be able to cheat in the mean time and bend the thermal spring in the front of the clutch to cause the fan to come on sooner.

have you considered running waterless coolant?

Waterless coolant runs even hotter.

 

[catbird7]

Most everything I've seen of your work is meticulous & well planned, therefore I'm wondering if your over heating problem is something obscure. You know my track record with champion radiators and I think you have one, is it possible there's a flow issue, some type of manufacturing flaw inside the rad restricting flow? I realize this is a stretch, however you've been up and down and all around this problem trying to correct it, maybe it's a problem inside the rad you can't see??? Another thing I thought about, are you certain there's no air trapped in the cooling system?

 

[Double-S-Diesel]

thinking out of the box here stuff that may have been checked.
IIRC the fan and wp on a IDI ran backwards from a PSD.
was there a difference between serp belt and v belt water pumps
what about the fan and fan clutch
is the fan spinning the right direction.
is the fan centered in the rad (Looks like it)
have you tried moving the fan closer to the rad, I have machines at work that this helped on.
is the trans dumping heat to the rad.
Just some thoughts I have

 

[CDX825]

What is your EGTs running?

 

[jetfly12]

The overheat light always kicked on at 242 degrees while towing over the Eisenhower tunnel with the some off name thermostat I used during the engine rebuild. An actual motorcraft thermostat fixed all my issues. Since I have installed a intercooler heat exchanger I have seen temps creep up to 230 and that is the highest its been since the motorcraft tstat install. 1200 EGTs is hard to keep an IDI cool so I also always try to keep it under 1000.

 

[subway]

Waterless coolant runs even hotter.

but you should not have to worry about it like regular coolant

 

[Booyah45828]

Boiling point for 50/50 coolant at sea level with a 15 psi cap is 265*F. At 250 I'd for sure be backing out of it because localized hot spots in the cylinder head will be well over that temp.

If you want to get scientific on it, measure the coolant temp at the lower radiator tank. Most have an npt petcock you can screw out and install a temp bung in it's place. That will tell you if the radiator/fan is functioning adequately. Check your gauge in a pot of boiling water too, I've seen them off as well.