Truck: 2005 F150 SuperCrew 4WD
Engine: 5.4L 3V, stock
Transmission: 4R75E, stock
Mileage: 121,000
Original owner

Tow package with 3.73 LSD, factory transmission cooler, and the larger factory radiator

Maintenance within 5K miles:

• New spark plugs
• Radiator flush, new coolant (but I didn't clean it -- just fluid change)
• Transmission fluid (series of pan drops to ~95% fluid exchange)
• Engine oil
• Pressure washed the radiator and transmission cooler

Transmission Gauge: Speedhut, installed in the test port on the side of the transmission.
Engine Coolant Temp Gauge: Speedhut, installed in the drain port on the driver side engine block.

Problem: My transmission and engine seem to run hotter than I would expect, especially given the heavy duty cooling this truck has. No coolant or fluid loss. No engine codes. No warnings. Just really hot and, when towing, hot enough that I pull over to cool down.

Condition 1: Commuting 13 miles at constant 50 mph speed with very few stops. Altitude of 5,000' and air conditioner on.
Ambient Temp: 65-70 F
Engine Temp: 190-195 F
Transmission Temp: 165-180 F

Engine seems normal and right on top of the 192 factory thermostat setting. However, the transmission seems high. I believe that the transmission cooler thermostat/bypass opens at 140 F and I'd expect it to run very near that temperature for such light duty work.

It's crazy to me that I'm driving around on a sunny 70F and my transmission is at 180 F.

Condition 2: Towing 6,300 lb trailer (weighed) with 550 lb of human beings in the cab. Freeway driving. O/D locked out. Running in 3rd gear at between 1,900 and 2,500 RPMs ... 40-60 mph. Some reasonable grades as the route climbs from 5,000 to 7,500' in about 60 miles. North-south driving ... not over the Rocky Mtns.

Ambient Temp: 80-85 F
Engine Temp: 210-240 F
Transmission Temp: 200-230 F

When the transmission temperature reaches 220 F, I pull over. The engine temperature is typically about the same temp as the engine, but at least once it reached 240 F (and was idling rough when I stopped). My gauges are good/accurate.

I only drive around 30 miles before there's just too much strain. But, I'm driving slow and keeping RPMs down. O/D is locked out, so I'm typically in 3rd gear. Rarely do I downshift to 2nd. Seems like I'm really babying the truck and the ambient temp is hot but not scorching.

Again, this just seems 20 degrees too hot from what I'd expect.

Condition 3: No trailer. Driving the truck up Pike's Peak, going from ~8,000' to 14,000' in around 17 miles. O/D locked out. Speeds between 15-25 mph. RPMs in the 1,500 - 2,100 range.

Ambient Temp: 45-55 F
Transmission Temp: 220 F
Engine Temp: 220F

Probably the last couple of miles I was pegged at 220F on both Tranny and Engine. Tough climb, but it was cold, I was going slow, and O/D was locked out. Again, it just seems too hot.

Condition 4: Towing the same 6,300 lb trailer. Towing the reverse of the freeway driving, so terrain is flat to slightly downhill ... with some ups/downs. O/D locked out. RPMs held in the 2,000 - 2,700 range as I went faster at 55-65 mph. I also turned my A/C off.

Ambient Temp: 80-85 F
Transmission Temp: 210 F
Engine Temp: 210 F

On some hill pulls (Monument, CO), I overheated and had to pull over (220/220 F). But the rest of the trip, with A/C off, I ran 210 F pretty consistent. Some stop and go traffic in Denver got me to 215 F and then some small hills also got me to 215 F. But, I could always baby it back to 210 F.

Nothing I could do would get the temps below 210 F. And, the transmission temp tracked the engine temp 1:1 the whole way.

Diagnoses:
When pulled over and at idle, if I rev to ~1,800 RPMs, my fan clutch kicks in as expected and it will cool the engine down 10 degrees pretty fast.

When I pulled over to cool down the truck (idling, hood open), the engine and tranny would track one another. Engine would settle in at around 200 F and tranny would go a bit lower to 190 F. Typically, when I started to drive away, the tranny would bottom out at around 185 and the engine would hit around 195. Again, ambient was ~85F.

In normal driving (e.g., Condition 1 above), the engine temp stays right around the thermostat setting of 192 F. I take this to assume that the factory thermostat is still working as expected.

When driving in cold conditions or when coasting down hills, my transmission will bottom out at 140 F. This matches up with the transmission cooler thermostat/bypass. That indicates it at least partially works and that my gauge is accurate.

Questions:
Am I running too hot, or is this just normal?

Is it possible that my radiator is shot?

Is it possible that my transmission cooler isn't flowing correctly? It was really hot to the touch, so there was definitely hot fluid in it. However, is it possible that it's somehow compromised? It seemed really strange to me that the tranny was linked so rigidly to the engine temp.

Not sure if there's a malfunction here, or if this is just the limit of this truck/engine.

Is there anything I can do to run cooler?

Thanks.

 

I sort of agree with you. First if coolant temp rises much above (~ 5 to 7 degrees) thermostat rating, assuming it is opening properly, the circulating fluid is not able to transfer heat out of the fluid. Seems to me that would indicate an obstruction in radiator or coolant circulation --- OR possibly some 'bypass' path for coolant to recirculate through the engine _Without_ going through the radiator. Ie: the heater core.


As for the Transmission - again I sort of agree - that seems too high. I would be curious if the Torque Converter clutch is locking up the TC like it should or slipping too much.


The 'heat' in the tranny is generated primarily by the its 'whipping up' the fluid between the input and output impellers. At a certain speed / load condition, the Torque Converter Clutch should lock the TC up and after that the tranny should not heat up any further or in fact cool down.


If you have live OBDII data capability (ie: Torque Pro scanner), Ford provides a 'wealth' of Transmission parameters that are presented on OBDII. Such as 'Transmission Main Line Pressure Desired (commanded) [PID 09D8]; Actual Transmission Line Pressure [PID 09AE]; Torque Convertor Control Pressure Commanded [PID 09AF]; Torque Converter Clutch Control (Duty Cycle) [PID 11B0] and Torque Convertor Slip - across torque convertor (in RPM) [PID 11B8]. Transmission Fluid Temperature [PID 1674].


There are a bunch of others - such as a power limiting flag for Transmission Over Temperature [PID 1105 -bit 2]. But monitoring the values from these would be most instructive.


I also think I would be cross checking the temperatures you are getting with a laser thermometer.

 

What antifreeze mix are your running? The more antifreeze to water ratio the less ability to transfer heat. Granted I'm in the desert but everything I run is 20/80 max.

Was 110 today and lots of stop and go, coolant hit 202 trans 182. And that's got 155k on it.

Also, use a scanner to compare your temps and is your air diverted torn? My trans used to run warm before i discovered it was, I could see the crank through the front bumper.

 

You may want to install a small auxiliary electric fan on the transmission cooler.

 

Thanks for the responses. I don't have any OBDII data capturing capability, so I won't be able to get into that level of diagnostic work.

I think I'm going to replace my thermostat as preventative maintenance and then try to use a radiator cleaning product. Maybe I have scaling and gunk built up from 13 years of use.

Same for the transmission cooler. I may disconnect it and attempt to flush it with a canned cleaner.

BTW, I run about a 50/50 mix. I could go thinner, of course, and get a bit more water in there for heat transfer.

 

The thinner mix changes by 10-15 degrees.

 

Quick update. I haven't been able to do much since my OP, due to some business travel. Just got back and did the following:

• Complete radiator flush. Coolant coming out looked great, BTW. Took about an hour and a half of slowly filling, running, draining, repeat ... until it looked like water coming out.
• Used 2 bottles of Prestone radiator flush/cleaner. Ran that for a couple of days and few hours of driving.
• Complete flush of the radiator using 10 gallons of distilled water and few fill/drain cycles.
• 1 gallon of Valvoline gold 50/50 premix coolant. 2 gallons of distilled water, plus whatever was still in the engine. This should be a 10-15% mix.
• 2 bottles of Royal Purple Ice (similar to Redline Water Wetter).
• Installed a new Motorcraft 192F thermostat (and o-ring).
• Complete disconnect of all of my transmission fluid lines. Blew them out with an air hose. All fluids coming out looks brand new.
• Blew out the transmission cooler.
• Used a transmission cooler cleaner can to flush out the cooler lines.
• Cleaned up the transmission cooler thermostat with solvent.
• Exchanged 6 quarts of ATF (I have a transmission pan with a drain).

I have no idea if any of those maintenance items will have any effect. We'll see. Everything that came out (fluids, parts) looked brand new. The lines are in great shape. I'm surprised at how well everything has aged. Anyway, I'll update as I'm on my way to Custer State Park in SD. Will be a good test for the truck.

 

Well, I'm back and I had mixed results.

First is the new baseline information. If I'm not doing anything at all, no towing (truck only), going straight, constant speed, constant RPMs, then my tranny sits at 160 F and my engine sits at 194 F.

If I do anything at all that requires a few shifts and RPMs into the 2,100 range, my engine is immediately between 200 - 205 F. Tranny crawls up to 170-180, depending on duration.

TOWING ...

When I'm towing, my transmission best case scenario is 190 F. If I'm coasting downhill, then maybe 180. My engine is pretty much 205 until I coast downhill and it will go all the way to 194.

If I lock in at 2,200 RPM and around 57-60 MPH in 3rd gear (O/D locked out), then my transmission will sit at 200 and my engine at 205 at ambient temps of 70-87 F. When the ambient rises to 95, the engine climbs to 210-215 and transmission to ~205. If I turn my A/C off, then my engine goes back to 205. Yep, A/C is about 10-15 degrees at high ambient temps. Seemed not to matter at 85 and lower.

Temps tend to scale with RPMs. If I keep it steady in 3rd and increase RPMs to ~2,600 and my speed to ~66 MPH, then my engine goes to 215 F, regardless of ambient temp.

If I downshift into 2nd or 1st, then my engine goes up with RPMs and my transmission goes up due to the shifting + RPMs. With that said, it seemed to be easier for me to maintain 220 F on both engine and transmission than my earlier trip. Granted, I was at lower elevations. Last trip, I was driving freeway from 5,000 to 7,500. This trip, I was freeway driving from 3,500 to 5,500.

The good news is that I never overheated to the point of pulling over. Each time I got up to 220, I relaxed and let things go back to 200/205 for tranny/engine.

I did have one issue: we were going through a drive-through bear park and pretty much just idling around for 30-40 minutes at 87 F ambient. After about 15-20 min, my engine was a couple ticks above 220 F and it started to shut down. Super rough idle at 250-500 RPMs and it wanted to die. I had to slam it into P and get on the gas ... tricky because we were in a line of traffic. Anyway, got my RPMs to 1,800 and the fan cooled it back down to 205 quickly. Kept my eye on it the rest of the way.

Not sure why my engine acted that way at ~223 F. Maybe my coolant mix was so thin that my coolant was boiling. I have a hard time believing that 10% coolant under pressure would boil a mere 10 F above theoretical pure water.

At this point, I have no clue what to do next. I've considered adding a second transmission fluid cooler in line with the factory one and maybe a deep fluid pan from Mag-Hytec (or equivalent) to hold 2 extra quarts. That, of course, doesn't help my engine temp, though. My A/C and heater both work great and it seems to move fluid around pretty well ... yet, it gets hot, fast.

Good luck.

 

Maybe my expectations are out of whack? Here's an older thread where various people comment on the 5.4. While some people live in the 195 range, there are a number of people who seem to live closer to 200 as "normal." Maybe my engine temp is where it should be.

The youtube video posted near the end shows a response that is similar to my truck. He starts off around 2,400 RPMs with a tranny/engine temp of 193/198, about 7 degrees cooler than I would be. When he downshifts and rides high RPMs, his tranny ends up climbing to nearly 230 F. However, his engine coolant really never gets above 210. I'd have been at 220 easily. Maybe that's natural variation, maybe altitude, maybe something else. Not sure.

Doesn't explain the weird overheating-ish idle nonsense I experienced, though.

 

You are a prime candidate for an electric fan conversion kit. The engine-driven fan is not pulling enough air at idle.

As I already said, put a fan on the transmission cooler.

 

Bigger radiator. Lower thermostat.

 

Lower thermostat will mess up the emissions calibration.

 

Definitely a big "No" to messing around with the factory thermostat. I'm sticking with Motorcraft 192 F stat.

As for a tranny cooler fan ... why? I have seen two recommendations, but no explanation why that would help. The factory cooler is in front of the radiator and I'm driving 50 MPH and greater ... so what's a fan going to do for me as I'm cruising down the highway? I get how they help at idle and in applications where the cooler is not in the front of the vehicle. I don't know how an electric fan helps my cooler work better when it's already exposed to 50+ MPH air flow.

I'd like to know more about the fan in my application. Thanks.

 

So this is going to seem half stupid but it was missing on my truck and made a 20 degree drop in temps. Do you have the air dam in place or can you look through the grill and see the balancer? Didn't think much of it that the push pins had ripped out of it, but when put back in place it made a HUGE difference.

 

I'm afraid I don't know what the balancer is or what you're specifically talking about. I'll make some assumptions and describe what's there.

First of all, my truck looks like this:



There is an open gap between the fog lights. On the very edges of this gap is some plastic molded honeycomb. But, the big middle section is open. I remember that this was called some form of the "missing piece" or the "trim piece Ford forgot" and so on. There was an aftermarket part that completed the honeycomb plastic pattern. Others have mounted LED lights and such in this gap. I have done none of the above. It's factory and the gap is still there -- unimpeded air flow (well, I do have a front licence plate that juts a bit into that gap). Similarly, I have nothing behind the grille that would impede or redirect airflow. It's all stock.

Behind this gap is essentially where the transmission cooler sits. Actually, it rides just above. Centered horizontally and vertically positioned right behind the thin copper/brown/body-color trim that separates the bumper from the grille.

Below the transmission cooler is a thick rubbery mat-like material that connect from the lower bumper to the lower frame underneath the radiator. This should direct airflow up into the transmission cooler and radiator. This is also intact and in perfect, factory-fresh repair.

Hope this answers the question.