Yesterday we took our 2007 FEH (4WD) up a fairly steep rough road (jeep trail) near Olathe, CO. It involved some steep inclines and probably gained ~1000 feet. Since the vehicle is essentially new (2 weeks old), I didn't want to go too far and we stopped halfway up and hopped on mountain bikes. We turned it off and got ready for our bike ride. Someone noticed some serious dripping under the car. Coolant was POURING out. This was not some minor drip, but a stream of coolant. I didn't think I hit anything and was concerned a hose fell off.

With the hood open, it was easy to tell it was the engine's coolant that was pouring out: the reservior was almost empty. When we released the cap, however, the tank filled halfway up and the dripping stopped! A quick inspection showed that all the hoses were intact. This was perplexing. There were no messages from the onboard computer.

We did get the vehicle back down and parked it over night. In the morning we filled the coolant back up to the line (50/50 per manual). In a few minutes what we put in was gone! So we added more. This time it stayed. Today we drove back to Colorado Springs and had no problems.

My questions to the group: has anyone seen this? Does anyone have a hypothesis for why it happened?

My guess is this: going slowly up the rocky road caused the engine to heat up. It was pretty steep and a lot of work to get up as far as we did. The increased heat and decreased ambient pressure (~7000 feet elev) causes pressure to build up in the coolent system. The pressure got so high, the coolant slipped out one of the hose seals. The coolant was doing its job (kept the engine cool) and thus the onboard computer didn't register it as a warning. When we opened the cap, the pressure equalized and backfilled the reservior. With things stable, the coolant system is now back in action.

Thanks for any thoughts. I need to decide whether to bring it in right away or if it fixed itself.

ryan

 

If nothing is loose or "broken" then my gut feeling is:

With all the steep inclines and bumping and jarring ( also the pressure difference with altitude ) the coolent simply "sloshed" out of the reservoir cap. Maybe the cap got loose, or exceeded the 17psi rating.
If it does not happen again, then don't worry about it.

Of interesting note, today I took mine up I70 over the divide with 3 adults and all the ski gear incl. roof ski rack. Had to run at 4000 RPM for like 30 minutes continuous. Even though outside temperatures were about 28-30 degrees and it was snowing, my coolent got hot also. About 200 degrees. Not dangerous, but much warmer than the Standard Op. Temp. of 184 degrees.

When I went through Vegas in July with 114 degree ambient temps and Max. A/C on, the car never exceeded 190'F.

???

 

I worked in a Ford dealership for over 10 years as a service tech. and have seen your concern several times. coolant leaks when hot and "fix" it's self after a cool down period. This is generaly caused by a weak or cracked hose clamp (Ford uses the spring clamp style) also often times it is also caused by the clamp retainer left on (a "U" shaped peice of metal that holds the clamp in a compressed state during assembly). Inspect all clamps, often if the clamp is cracked it will break if compressed. this condition is not normal and you should bring the vehicle back to the dealership for service. Your vechicle is still in it's "break-in period" so the last thing you would want is your FEH to overheat.

 

I wonder if this is one of those circumstances where the ICE is not only running continuously, but also running hard?

I would think that for most of us, we would never push the ICE enough to test if its cooling system is adequate for the most demanding loads.

 

Others have reported no problems in moutain passes, so I'm more suspicious about that particular vehicle than a design issue. Engine heating is something that all cars have to deal with, and in reality there is nothing different in this car in that respect other than a higher RPM, and you'd think they'd know how to handle that..

I'd find it hard to believe they'd mess the cooling system for the ICE up...

 

Anti-freeze running onto the ground, coolant reservoir was empty, when the radiator cap was loosened slightly(??) coolant in radiator flowed into the reservoir.

It is not at all unusual for the coolant temperature to rise, sometimes dynamically so, when a HOT engine is shut down after a HARD pull wherein the coolant is already at or near the boiling point. Most systems have a thermostatic switch that keeps the radiator cooling fan running if the coolant temperature is elevated, even after the ignition key is removed. I can certainly understand why this might not be the case with the FEH/MMH, smallish 12 volt batttey and the DC-to-DC down converter would undoubtly be shut down.

As a rule if the coolant reached the point of boiling, or even only expanding dramatically due to the rise in altitude and high engine work load, the radiator's pressure relief/bypass cap would automatically open to allow the excess pressure/fluid to flow into the reservoir.

Once the reservoir overfills the reservoir's excess fill will get dumped onto the ground.

But your reservoir was empty....

The way it should work.

Heat exchangers, your radiator, are at their most efficient when the temperature differential between the outside air and the coolant is at its greatest. Water, "coolant", boils at 212F at sea level. So keep the coolant from boiling until its temperature reaches ~240F, take it below sea level by pressurizing the system.

As the coolant volume within the system, engine, radiator, etc, increases due to engine heat, the pressure will eventually increase enough to overcome the pressure bypass spring in the radiator cap and coolant will flow into the reservoir until the radiator coolant pressure is low enough.

This pressure bypassed radiator outflow will ALWAYS be into the bottom of the reservoir for reasons that will soon become obvious. The reservoir fill cap will be at the top and will typically be reasonably well sealed except for a fairly small "bleed" hole/orifice.

When the engine is shut down and now the coolant slowly cools to OAT a slight, very slight, vacuum will develop and that will result in syphoning, "pulling", the coolant from the reservoir back into the radiator. The inflow/outflow tube in the reservior must be at the bottom of the reservoir, immersed in any remaining coolant.

But your FEH maintained a vacuum, apparently a fairly srong vacuum, for an extended period with the reservoir practically empty.

How can that be.

Aha, a float valve within the reservoir.....

A float valve that closes the return path, syphon path, from the reservoir to the radiator, unless they is coolant in the reservoir to be "returned" to the radiator when the vacuum develops due to the coolant temperature declining.

So here's what happened to you.

The float valve in the coolant reservoir become stuck shut due to the lack of sufficient coolant. How many hest/cool cycles might it take for there to be so much vacuum in the radiator system that the float valve is forced so thoroughly closed that it STICKS closed.

Now you do an extraordinary, non-everyday thing, you tax the radiator beyond its normal, everyday, limits. Even more coolant is PUSHED out of the radiator. But where will it go, something has to give, right?

So much pressure is built up within the radiator and hoses downstream of the radiator that your coolant is FORCED out at the hose clamp interface area.

The next day the engine/radiator/coolant is at OAT and as a result of the STUCK float valve there is a HIGH vacuum within the engine/radiator coolant system. You add water to the reservoir, your "boat"(float) floats, the float valve opens as a result and the reservoir contents begin to be symphoned off into the radiator.

But what started this process..??

The coolant level may have been too low when you picked it up at the dealer and only the extraordinary circumstance resulted in a "failure". If you don't remember ever smelling anti-freeze during the previous two week I would guess that to be the case.

If you didn't smell anti-freeze at all during that timeframe then I would suggest returning your FEH to the dealer ASAP...NOW!

PS: The idea of a float valve in the reservoir is only a guess given your overall circumstance. I have never encountered one nor read of one but it seems to make some sense to have a float valve in the reservoir to prevent the system from "sucking" air once the coolant is exhausted. Let me know the outcome, please.

 

Thanks everyone for your insightful replies. There is a wealth of knowledge among us. I bring the FEH in for service tomorrow and will post what Ford finds.

ryan

 

While you may have a faulty hose clamp, I suspect the problem is likely due to a very hot engine being shut off. My suggestion is to let the engine cool off for a few minutes after stopping before letting it shut off. While the ICE is running, put the FEH in neutral. Neutral will prevent the ICE from shutting off (or starting if it is off when you put it in neutral!) and let it idle for a few minutes.

I have towed horses for years with an F150, and always let the engine/tranny cool off by idleing a few minutes after a long trip. Still have the same engine and tranny in the truck (no rebuilds) after 250,000 miles

I have an '05 FEH and have climbed Sonora pass in the summer without a problem. Sonora pass is in central California and is a steep climb of 10 to 15% grades, with sections of 26% going up and down from the summit at 9624 feet Quite a climb and the FEH handled it great loaded with camping gear and two adults!

 

The fans are electric in the FEH and can and DO run even when the key is out/engine is off if the system is very hot.

The coolent pumps are electric and will continue to circulate the coolent even with the engine OFF ( not sure if they will with key out ).

DO NOT do what the previous posted suggested ( force engine to stay on ).
This is totally UN-needed and will waste gas.

Your FEH will cool off quickest in EV mode, key on. For Sure.

 

".. do run....when the key is out....if the system is very hot..."

Are you sure of this, CERTAIN sure..??

"...coolant pumps.. will continue to......"

Obviously you're uncertain of "this".

Since it is the METAL engine block that has been, potentially, overheated/overstressed you must be CERTAIN that the radiator cooling fans will run in EV mode as will the coolant pump. I would assume both of these are 12 volt devices and thereby powered from the 12 volt battery which in turn relies on the DC-DC down-converter from the hybrid battery for its own state of charge.

In the conditions related aren't the chances quite LOW that the hydrid battery had a reasonably high level of charge?

"...fairly steep rough road (Jeep trail).." "..involved some steep inclines.."

Seemingly, assuming speed was mostly DEAD SLOW (Jeep trail), there would have not been much opportunity for the use of regenerative braking to keep the hybrid battery charged. "Dead slow" would also imply that the electric motors were in continuous heavy use and with only the ICE "excess" power to use for recharging.

Lots of good reasons for why the FEH/MMH series nor the RX/HL hydrids are NOT qualified, NEVER to be used, for off-road, " Jeep trail", use.

Bottom of the line is that the coolant may have boiled regardless of the operation of the radiator fan and coolant pump.

With HEAVY use of the hybrid battery being highly likely did the system need the A/C to keep them cool. More loading of the ICE and a substantial lowering of the efficiency of the engine cooling system.

Most A/C's will automatically shut off if the engine water jacket temperature is threatening to reach criticality, but maybe not the FEH/MMH since it is used to cool the hybrid battery?