Hi folks, first post... Unfortunately it's because of a problem that's driving me nuts!

I have a 2004 E350 Super Duty cargo van that I use for work. 395k miles on the 5.4L and I'm chasing an overheating issue. I've read all the threads here I can find and I haven't been able to decipher a final solution. So here's what's happening...

I had an upper radiator hose blow out rather violently a few months ago on the freeway. I was able to pull over before the temp redline, so I don't think any internal damage was done. Shortly after that, my lower hose started leaking because the bracket came off and it started rubbing on the steering linkage. After replacing that hose, I started noticing that temps would rise in stop-and-go traffic or going up long inclines on the highway when outside temps got to be in the low 80s.

What I've done so far... Replaced a bad fan clutch, new thermostat, new reservoir cap, new upper and lower hoses, chemical flush of cooling system. I don't get any white smoke out the tail pipe, there is no sign of oil in the coolant nor coolant in the oil.

I can idle all day long regardless of outside temps with the AC on with no problem. When the temp gets too high or I can't get out of a stop-and-go situation, I'll pull over, put it in park, leave it running with the heat blowing and the gauge will calm down. If it acts up while going up hill, it will cool off when it levels off or starts going downhill.

I just got a scanner that allows me to watch live data and an IR thermometer so I can try to get a better handle on the actual temps. This morning it began to act up on my way to my first job, so I read the temps... The scanner showed 234° but the IR reading on the thermostat housing was 195°, 190° on the upper radiator hose, 160° on the lower radiator hose, and about 178° on the one crossover tube that I could read without pulling the air filter housing off. Note that this was only a mild start of the issue, I was just curious what the readings were at this point. I'm gonna do the same readings this afternoon when the temps really go up.

The upper radiator hose does get solid, I do not lose coolant, and there isn't any signs of boiling over. No engine codes are being thrown.

At this point, I'm thinking it's possible that I have a bad temp sensor, but I don't want to keep throwing money at it in hopes to fix it. Also curious if a transmission issue would cause the coolant temp to rise. If so, what would I look for in that regard? The trans fluid is good and at proper level. I had the trans rebuilt a couple years ago and haven't serviced it since other than watching the fluid.

The cats failed a few months ago and I just had them straight-pipe the exhaust until I can afford to replace them... Would the computer mess with the fuel mixture differently with the higher outside temps and adversely affect the coolant temps?

Sorry for such a long read, but I wanted to throw out as much info as I could. If any more info is needed I'll be happy to provide.

Thanks in advance for any help you guys can provide. 🍻

 

If not boiling over really probably the temp sensor. 234 is high but not dangerously and pulling hill will get that high. normal temps are indicated on the scanner so would really change the temp sensor. Also pressure check the 'new' cap these allow a lot of issues and for 5-10$ can be a pia. When I changed mine on my trucks had to pressure check 4-5 before I found 2 good ones. 1 for me other for son with 5.4.

Forgot to ask, is the rad fan coming on at the hi temp?

 

If you have a trans cooler in the radiator an overheating trans can cause an issue. I had this in my '92. Got an external cooler and disconnected the one in the radiator. Solved my temperature creeping up on long hill climbs especially with the ac on.

 

I purchased the cap from Ford because I wanted to be sure it would be correct. When the temp is reading high, in stop-and-go traffic, I'm not hearing the fan kick in... Another reason I'm starting to think the temps aren't as high as the computer things they are.

I read that there are multiple temp sensors on the 5.4.. which sensor is the one that would need replacement?

 

I believe it's an external trans cooler mounted in front of the radiator, but I need to confirm to be sure.

 

Update: I ran around town with the AC on until the temp got up to 250° on the scanner. I pulled over and shot the temps with the IR and I didn't get any readings over 212° at the stat housing or upper hose. The lower hose read around 185-188°

 

So I let the van get into the red to see if it would throw a code and it did say the cylinder was overheating. If this is really the case, wouldn't the actual coolant temps reflect a problem? The scanner showed 250+ degrees, but the thermostat and upper hose never got above 212°.

If the scanner temp is correct and a cylinder is actually overheating, I assume the head gasket is blown but like I said in the original post, there's no sign of oil and water mixing.

 

At this point, I think you are safe in replacing the temp sender.

 

Okay, finally located and replaced the sensor this afternoon... Will report back tomorrow how it goes.

 

So how did it go? Is it still overheating or did the new sensor fix it?

 

 

Consider the surface you are measuring with the IR gun too, its not uncommon to read much lower temps on a reflective or bare metal surface. Rubber hose also reads much lower. I have had luck in the past painting a surface with a flat black spray paint.