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

[orion]

So I don't think you've read through the back and forth on here, but if you have, forgive me for repeating this.

The Bronco overheated on a dirt road in the middle of nowhere. I checked the coolant and the tank was filled above the max line. The heater was blowing cold air. We let it sit for a half hour and then drove for a while until it overheated again. I pushed it for a few miles. I drove it to the top of a hill and turned it off and coasted down a mile or so. We then took 20 minute breaks and then drove for 5 minutes. The failsafe engaged where the cylinders start to alternate. Eventually, we made it to the pavement where I left it sitting next to the Colorado river in the dark. We hitchhiked back to cell service, got a hotel room, and then I found a tow truck the next morning. When I left it in the dark, more than three hours after it had overheated, the tank was completely full of coolant and there had never been any evidence of any leak.

The hottest the temperature got and when the failsafe was fully engaged was at the very end, when we were getting it to a safe place. If the hose popped off after we left it, we would have never seen it since the two truck driver picked it up.

I think your hose disconnected leading to total coolant loss in the system, engine and radiator. The tank you are talking about is the over flow tank. It might have to have pressure in it to push back into the system therefore never drained. I don't think you over heated till coolant loss happened and if my assumption is right about pressure putting coolant back into the system, whether it be positive, hot, or negative, cooling, in an open system it probably would stay in the over flow tank.

Hopefully that makes sense and it's just an assumption.

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[Someguy]

Did the dealer reconnect a hose AND add coolant, or just reconnect the hose?

There would be coolant in that tank if the system had a hose off and wasn't pressurized correctly. You might have missed the coolant leak as it could have just poured out quickly as you were driving.

Popping from pressure at the trans doesn't sound as likely to me as the hose coming loose either through being not secured properly from the factory or an off-road hazard...so if the hose is tight now I'd drive for a bit near the dealership and feel ok about heading home.

I would have the tools or clamps needed to put the hose back and I'd be carrying extra water or coolant, just to be safe.

 

[jb56]

I think your hose disconnected leading to total coolant loss in the system, engine and radiator. The tank you are talking about is the over flow tank. It might have to have pressure in it to push back into the system therefore never drained. I don't think you over heated till coolant loss happened and if my assumption is right about pressure putting coolant back into the system, whether it be positive, hot, or negative, cooling, in an open system it probably would stay in the over flow tank.

Hopefully that makes sense and it's just an assumption.

That make sense to me. Thanks!

 

[jb56]

Did the dealer reconnect a hose AND add coolant, or just reconnect the hose?

Possibly, there would be coolant in the tank if the system had a hose off and wasn't pressurized correctly. Popping from pressure at the trans doesn't sound as likely as it coming loose either though...so if the hose is tight now I'd drive for a bit near the dealership and feel ok about heading home.

I would have any tools or clamps needed to put the hose back and I'd be carrying extra water.

Good idea.

Yes, they added coolant. I'll probably bring coolant with me and the tools I need. I'm trying to find a diagram that will show me exactly what hose they are saying was disconnected. I know that engine coolant sometimes also cools the transmission, but I'm not that familiar with what hose that would be. I'm not there so I can't have them show me.

 

[Ksjrb03]

Im not a mechanic and will be the last to give authoritative advice on an issue like this. But I will say I would trust the dealer knows what they are talking about generally. If they say the hose was disconnected and coolant was empty, I would believe them. My one question to them would be did they run the engine and let it get up to temp for a good period of time before I pick it up and journey home.

 

[flip]

Item	Description
1	Radiator
2	Transmission fluid heater coolant control valve inlet hose
3	Transmission fluid heater coolant control valve
4	Lower radiator hose
5	Coolant pump
6	Coolant inlet connector
7	Thermostat
8	Transmission fluid heater coolant control valve outlet hose
9	Radiator-to-degas bottle hose
10	Upper radiator hose
11	Coolant outlet hose
12	Degas bottle hose
13	Degas bottle
14	Engine oil cooler inlet hose
15	Engine oil cooler outlet hose
16	Cabin heater coolant pump
17	Heater inlet hose
18	Air aspirator hose
19	Turbocharger RH inlet hose
20	Engine oil cooler
21	EGR cooler
22	Turbocharger RH
23	EGR cooler outlet hose
24	Heater core hose assembly
25	Turbocharger RH outlet hose
26	Cylinder head to coolant outlet connector hose RH
27	Coolant outlet connector
28	Cylinder head LH
29	Heater core
30	Cylinder head to coolant outlet connector hose LH
31	Turbocharger LH outlet hose
32	Turbocharger LH
33	Turbocharger LH inlet hose
34	Cylinder head LH gasket
35	Cylinder block
36	Engine front cover
37	Transmission oil cooler
38	Transmission oil cooler inlet hose

 

[Nobody]

So I don't think you've read through the back and forth on here, but if you have, forgive me for repeating this.

The Bronco overheated on a dirt road in the middle of nowhere. I checked the coolant and the tank was filled above the max line. The heater was blowing cold air. We let it sit for a half hour and then drove for a while until it overheated again. I pushed it for a few miles. I drove it to the top of a hill and turned it off and coasted down a mile or so. We then took 20 minute breaks and then drove for 5 minutes. The failsafe engaged where the cylinders start to alternate. Eventually, we made it to the pavement where I left it sitting next to the Colorado river in the dark. We hitchhiked back to cell service, got a hotel room, and then I found a tow truck the next morning. When I left it in the dark, more than three hours after it had overheated, the tank was completely full of coolant and there had never been any evidence of any leak.

The hottest the temperature got and when the failsafe was fully engaged was at the very end, when we were getting it to a safe place. If the hose popped off after we left it, we would have never seen it since the tow truck driver picked it up.

Heater blowing cold is a common symptom of air in the system. Also once air is in the system, the temperature sensors will no longer be accurate.

What you describe leads me to believe the most plausible explanation is the hose came off first.

I know that is not what you want to hear. Lets just hope you limping along saved your engine from any permanent damage.

 

[Someguy]

Good idea.

Yes, they added coolant. I'll probably bring coolant with me and the tools I need. I'm trying to find a diagram that will show me exactly what hose they are saying was disconnected. I know that engine coolant sometimes also cools the transmission, but I'm not that familiar with what hose that would be. I'm not there so I can't have them show me.

It's a good exercise to know what went wrong and where, especially so that you can be confident you'll be able to sort it out yourself if you're ever in the same jam. That being said, being ready for this will probably guarantee it'll never happen to you again.

 

[jb56]

Heater blowing cold is a common symptom of air in the system. Also once air is in the system, the temperature sensors will no longer be accurate.

What you describe leads me to believe the most plausible explanation is the hose came off first.

I know that is not what you want to hear. Lets just hope you limping along saved your engine from any permanent damage.

It is actually what I want to be true. A cheap and easy fix with no waiting for parts. So that’s great.

I just don’t want to have it overheat again 30 miles outside of Moab. And it seems like the built in failsafe is meant to prevent component damage. So fingers crossed

 

[dgorsett]

The reservoir requires vacuum caused by coolant cooling and 'shrinking' in volume to get back into the engine. With a disconnected hose there is no vacuum, therefore reservoir can remain full. Dealers explanation sounds plausible.

Be sure to check coolant often as when air purges from the system the reservoir level may drop through several run cycles.

 

[flip]

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

 

[Silver-Bolt]

There shouldn't be engine coolant lines at or over the transmission. The transmission cooler lines go forward toward the radiator.

There have been many reports of the spring clamps (hose clamps) not fully seated in place. As pressure and heat build the hose will pop off. I have seen it on Broncos and F150 Raptors.

 

[Gassyjack]

Thanks flip, that was worth a thousand words.

 

[VoltageDrop]

There shouldn't be engine coolant lines at or over the transmission. The transmission cooler lines go forward toward the radiator.

There have been many reports of the spring clamps (hose clamps) not fully seated in place. As pressure and heat build the hose will pop off. I have seen it on Broncos and F150 Raptors.

It's different on these modern Fords. Look at @flip's diagrams and you'll see engine coolant goes to a cooler on the transmission for the 2.3L and in front of the front suspension crossmember on the 2.7L. I thought all modern Fords used cylinder head temperature sensors so the PCM should know the temperature even if the coolant system is empty so hopefully no damage should be possible.

 

[jb56]

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

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.

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