I have an 06 F-250 with 122,000 miles. When driving empty at 70-75 mph the coolant temp runs 194-200 and the oil temp 5 to 10 degrees higher at the most. When I pull my travel trailer the coolant temperature will start to steadily climb then abruptly drop down under 200. I have seen the coolant temperature pass the oil temperature when this happens.

The last time I pulled the trailer I was driving at 60 mph and the coolant temperature climbed to 220 then dropped to 196. A few miles later it climbed to 230 then dropped to 200. While the temperature was climbing I slowed to about 45 mph. As it was dropping I accelerated and the temperature continued to drop.

I have flushed the cooling system, replaced the thermostat and cap with no improvement.

The pickup has an SCT tuner set to street 1 and I was told by the previous owner that the egr was deleted, but the stock egr cooler is in place. It is possible that a plug was put in. I pulled the egr valve and the carbon coating on it is gooey like it has been wet.

I'm looking for guidance from anyone who has had similar symptoms as to what needs done.

 

Do your cold soak temperatures between oil, coolant, and transmission temperature agree? Verify your sensors appear to be correct first.


Do you hear the fan kick on? Mine will sound like a jet at 207 F water temperature. It will knock several degrees off of water temperature within 15 seconds.


Does the increase in temperature follow an increase in load? Is there any pattern to it, or does it randomly run up in temperature, independent of load?


If your EGR is deleted by plugging the gas side, and your EGR valve is wet, could you have a cooler leak? Also, if the gas side was plugged, I would think your EGR would remain clean (assuming it starts out clean).


I may start with the thermostat, even though you just changed it. It appears you have the ability to exchange heat at the radiator, you may just be having problems getting enough coolant there.


Good luck.

 

Not quite sure I follow on the cold soak temperatures. Under normal driving the coolant temperature is normally 194-200 with the oil temperature being 5-10 degrees higher. The transmission temperature is always around the 155 mark, it does not seem to increase when the coolant and oil temperatures climb. When it is tending to run hot I have seen the oil temperature 20 degrees hotter than the coolant temperature. I have also seen the coolant temperature climb a few degree higher than the oil temperature before dropping back down.


I hear the fan kick on most of the time at 216 F. Other times I'm not sure if it is running full blast or not due to too much road noise or passengers who don't know how to be quiet and listen. Is there a way to determine if the fan is running at full speed?


The increase in temperature is random. I can be on level ground at a very light throttle and the temperature will start to increase. When it does it will continue to increase even when I let off the throttle. When the temperature starts to drop it will continue to drop even if I increase the load.


I do think it is possible there is a cooler leak. If it really is plugged on the gas side it was done before I got it. My assumption is that the EGR had the carbon on it before the delete was done and was never cleaned.



Changing the thermostat again has crossed my mind. I put a parts store thermostat that was most likely made in China in it on a Sunday when we were on the road about 400 miles from home a couple months ago. I should try one from the dealer.

 

Let it sit for 12+ hours and see if the oil, coolant, and tranny temps are within a couple degrees. Just helps to verify the sensors are trustworthy.


I use a ScanGauge to watch vitals. I bought mine from BPD and it wasn't programmed with fan speed, but you can program it for fan speed.


I believe I have read that the oil temperature and coolant temperature sending units are interchangeable (check me on this). You may be able to swap units and see if the oil temperature now acts like the coolant temperature. This would help confirm whether you've got a real problem or a sensor problem. This being said, since it only shows up under load, I'd lean against it, but may still be worth the time.


A quality thermostat may be worth the investment.


Lastly, you may flash back to stock. I don't profess to having a reason why the tune would make your truck act like it does, but going back to stock will eliminate the tune as a contributor. Reducing your variables is a step closer to finding the answer.


Hope you get it resolved. Let us know what you find out.

 

Buy a Scan Gauge at Advance Auto using code TRT30 and save $50 off the price. They all require programming. Buy on-line, do in store pick up and program the 6.0 PIDs to check coolant, oil and fan speeds without having to swap sensors around to verity they are working after a cold soak. You DO NEED a device to monitor your trucks vital, bite the bullet and save yourself the headache later.

The tranny can take 225* without many issues, I wouldn't use that to compare oil and coolant of the engine. It runs around 160-165 normally and even towing won't see much above 180.

It is possible that the plug welded in place has burned through, not unheard of. You could remove the EGR valve and start the truck, if you feel hot exhaust, you'll know that to be true. Normally moisture in the EGR cooler is a ruptured cooler and requires replacement or deleted. Not sure how comfortable I'd be with coolant inside the EGR and depending on your location, a delete may be in your near future or a correction the the one you have may be needed.

They call it a stealth delete.... it's so good, you can't tell.

 

When I started it after sitting about 8 hours the coolant, oil and transmission temperatures were within 4 degrees of each other and no more than 10* above the ambient air temperature.

I don't think it is a sensor problem because both the coolant and oil temperatures increase.

I have an Edge Insight monitor. I don't think it will show fan speed, I'll have to research that.

 

I have an Edge Insight monitor, that is where my temperatures are coming from. I need to see if it will show fan speed.

The transmission temperature stay constant even when the coolant and oil temperatures are climbing.

I will pull the EGR valve and feel for exhaust gas tomorrow when it is cold. I will replace the EGR cooler just because I think it may be leaking and will do the plug so the up pipe has the cooler as support.

 

Just because its plugged from getting exhaust, you'll still need to watch oil cooler temps to avoid future EGR ruptures.

Be careful to not burn yourself, I'd recommend placing something over the opening as the temps can be cause third degree burns instantly, maybe a piece of wood.

 

I had a similar issue. I replaced the thermostat and it went away. I think it just didn't open fast enough. The new one has been in for over a year with no issues. Ford part.

 

Did yours do it all the time or just when towing?

 

I have some new information.
I pulled the EGR valve and started it. At an idle there was suction into the intake, no pressure from the exhaust. It must have been plugged. There is moisture so I'm sure the cooler is leaking coolant.

After more research last night I put a pressure gauge on a tee inline with the degas bottle. After the thermostat opened it held 10 psi. I got on it and saw 30 psi of boost. While doing this the coolant saw 17 psi quickly, enough to push it out the cap if I didn't have a hose clamp that let it past first. After letting off the throttle and driving normal the coolant pressure dropped back to 11 psi after two or three miles.

 

It sounds like you have headgasket problems.

I suppose it is not out of possible that you have both a gas side and coolant side leak in the EGR cooler. The gas side leak may not show up at low exhaust pressure. When your under high boost, the plug leaks into the gas side, and with no path back to the intake, it gets into the water side.

That being said, I think that's unlikely, and if you left your EGR valve out during the drive, it goes out the window.

The combustion gases will drive up coolant temp, but I still think you have some thermostat issues as well.

I have an Isspro 0-40 coolant pressure gauge I just rigged up tied it to the spare port on my Sinister filter. I've made a couple 20 psig boost runs with a 1-2 psi change in gauge (8-10, 9-11, etc.). Hard to know if this change is due to headgaskets or a higher dP across the filter at higher water flows. One day I'll close the inlet valve and register something closer to degas bottle pressure. Anyway, will be towing in a couple weeks so I'll see how it does under sustained boost. But 17 psig in the coolant system on one unloaded run is no bueno.

Good luck.

 

Snip:


The fan, running full speed, is VERY noticeable. I agree with the advice to get something to monitor fan speed.