UPDATE: Great day in Moab until my Bronco broke down (Overheating)

[indio22]

2.7L EcoBoost (238kW/324PS)

Item	Description
1	Transmission fluid heat exchanger
2	Transmission fluid heat exchanger inlet tube
3	Transmission fluid heat exchanger outlet tube
4	Transmission fluid heat exchanger coolant control valve
5	Transmission fluid heat exchanger coolant inlet hose
6	Transmission fluid heat exchanger coolant outlet hose

Interesting, so if I'm understanding that diagram correctly, rather than have the transmission fluid line run into the bottom of the radiator for cooling (old school method), instead these engines have a separate heat exchanger for that process. And since coolant hoses need to bring coolant to that separate exchanger, there is possibility for a hose coming lose there. Which sounds like happened per the dealer. Kind of bites to have that added complexity and failure points.

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[JediMcMuffin]

Flip, what do you think about this?

I just called the dealership again and I told them I am 100% sure that the coolant in the reservoir was totally full. They told me that when they checked it (so three full days later) that the coolant reservoir was totally empty. They said that when the transmission cooler inlet hose came off, it drained all the coolant out.

So I told them that it was completely full more than 3 hours after it first overheated, and I asked it if it was possible that the hose popped off after we parked it, and the service rep said he didn't know and he wasn't a tech, and the tech can't call me, but he said the tech didn't think there was anything to worry about.

I'm not going to hold anyone here to this, but I'm going to be picking this car up at 10:00 PM on a Saturday and driving it 200 miles in the dark.

Just keep in the mind that the tank up to is an overflow tank. It's not fully indicative of how much coolant is in the system. Depending on how the system interacts with it gravity along might have kept that fluid there.

 

[indio22]

Flip, what do you think about this?

I just called the dealership again and I told them I am 100% sure that the coolant in the reservoir was totally full. They told me that when they checked it (so three full days later) that the coolant reservoir was totally empty. They said that when the transmission cooler inlet hose came off, it drained all the coolant out.

So I told them that it was completely full more than 3 hours after it first overheated, and I asked it if it was possible that the hose popped off after we parked it, and the service rep said he didn't know and he wasn't a tech, and the tech can't call me, but he said the tech didn't think there was anything to worry about.

I'm not going to hold anyone here to this, but I'm going to be picking this car up at 10:00 PM on a Saturday and driving it 200 miles in the dark.

Maybe you and dealer are confusing the coolant expansion tank with the transmission heat exchanger tank?

The expansion tank could very well have had lots of fluid in it, regardless if the engine and radiator lost all the fluid. Because as mentioned the expansion tank fills up as engine heats up, and short of a leak in the expansion tank itself, the only way fluid goes back to the engine, is if vacuum pulls it back (which would not have happened once the main system was breached).

Maybe dealer is referring to the heat exchanger tank having had no fluid.

 

[flip]

Flip, what do you think about this?

I just called the dealership again and I told them I am 100% sure that the coolant in the reservoir was totally full. They told me that when they checked it (so three full days later) that the coolant reservoir was totally empty. They said that when the transmission cooler inlet hose came off, it drained all the coolant out.

So I told them that it was completely full more than 3 hours after it first overheated, and I asked it if it was possible that the hose popped off after we parked it, and the service rep said he didn't know and he wasn't a tech, and the tech can't call me, but he said the tech didn't think there was anything to worry about.

I'm not going to hold anyone here to this, but I'm going to be picking this car up at 10:00 PM on a Saturday and driving it 200 miles in the dark.

There are a few possibilities. You had coolant in the tank, there was enough air in the system that it caused it not to completely drain. If you look at that first pic I posted the drain hose from the reservoir over to the pump isn't that big and not a ton of drop. The air plug theory makes sense to me. After it cooled off there was a vacuum created which allowed the tank to finally drain off.

If they say they've got it fixed I'd take their word for it. Don't be surprised if you hear some gurgling or other noise from the dash area for awhile. Sometimes even vacuum bleeding these systems is a pain and it might take a few drives before the air completely gets worked out of the system. I'd also suggest getting the oil changed since they did verify it overheated simply as a precaution.

 

[Felix808]

I wasn’t even aware a coolant hose ran to the transmission.

It goes to the transmission cooler (2 lines), which is a heat exchanger.

 

[jb56]

Maybe you and dealer are confusing the coolant expansion tank with the transmission heat exchanger tank?

The expansion tank could very well have had lots of fluid in it, regardless if the engine and radiator lost all the fluid. Because as mentioned the expansion tank fills up as engine heats up, and short of a leak in the expansion tank itself, the only way fluid goes back to the engine, is if vacuum pulls it back (which would not have happened once the main system was breached).

Maybe dealer is referring to the heat exchanger tank having had no fluid.

We made sure we were talking about the same tank, by position, color, and what is on the cap. The dealership service rep says that tank that was full past the max line was 100% empty when he checked it.

 

[jb56]

There are a few possibilities. You had coolant in the tank, there was enough air in the system that it caused it not to completely drain. If you look at that first pic I posted the drain hose from the reservoir over to the pump isn't that big and not a ton of drop. The air plug theory makes sense to me. After it cooled off there was a vacuum created which allowed the tank to finally drain off.

If they say they've got it fixed I'd take their word for it. Don't be surprised if you hear some gurgling or other noise from the dash area for awhile. Sometimes even vacuum bleeding these systems is a pain and it might take a few drives before the air completely gets worked out of the system. I'd also suggest getting the oil changed since they did verify it overheated simply as a precaution.

Ok. Well, worst case scenario I'll have another weekend adventure. I'll give it a shot and see what happens.

 

[jb56]

Just keep in the mind that the tank up to is an overflow tank. It's not fully indicative of how much coolant is in the system. Depending on how the system interacts with it gravity along might have kept that fluid there.

While this makes sense to me, the dealership told me that with this hose being disconnected, the coolant reservoir would completely drain. Flip's theory does make sense though, because as everything cools the pressure changes. That high pressure could have kept it from draining and the low (cold) pressure may have let it drain.

 

[2112]

So, would one replace the water pump in the near future assuming that running dry for a length of time just shortened it's life span?

 

[Bmadda]

So, would one replace the water pump in the near future assuming that running dry for a length of time just shortened it's life span?

No, water doesn't lube the pump, it has a permanently sealed (we wish at least) bearing. w/no water it just acts as an idler pulley

 

[Neigh]

Also once air is in the system, the temperature sensors will no longer be accurate.

Wait a minute. Did Ford stop using Cylinder Head Temperature sensors that measure the temperature of the metal?

 

[Nobody]

Wait a minute. Did Ford stop using Cylinder Head Temperature sensors that measure the temperature of the metal?

I'll be the first to admit that I don't know shit about these modern engines. The
point I was trying to make is when there is air in the cooling system, it's not going to function as expected, and the coolant level can't be trusted.

 

[Ford Motor Company]

Hey Everyone who is still following this. I'm hoping that maybe you can help me understand what is going on.

So in the bronco there is a coolant reservoir/tank. When my Bronco overheated, that coolant reservoir was completely full, above the max. It was also completely cold even though the engine was overheating.

According to the Ford dealership, the hose that connects to the transmission had come off, either it was pulled off or "pressure" popped it off. The dealership says that the vehicle was completely out of coolant as a result of the hose coming off. I'm really confused about this because I didn't see any leaks of any kind. I didn't see anything wet at all. There was no steam or smoke or anything.

Can anyone think of why the reservoir would stay completely full if the coolant was leaking where it crosses over the transmission?

And why would that hose just pop off from pressure?

I'm just a little worried about driving it 200 miles on the highway when all they have done is just reconnect that hose.

Good morning. Could you privately message us with your VIN and the name and location of your Ford dealer so I can look into this overheating concern for you? Thank you!

 

[rtazz17]

Good morning. Could you privately message us with your VIN and the name and location of your Ford dealer so I can look into this overheating concern for you? Thank you!

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[Billnchristy]

I would think that once the heat exited the system the expansion tank would drain through the open hose. It was likely airlocked from the heat in the system and once it cooled down overnight the tank drained.

Just my guess.

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