I have the 4.7. We've had problems off and on with it running hot, but of course, as soon as a mechanic got near it, the problem could not be replicated. Took a trip to Florida Sunday, It ran hot, but it was full of water. Second time it ran hot it had no water it in. 3rd time it stalled and temp gauge was reading fine (even though it was out of water b/c my brilliant step father forgot to put the radiator cap back on it). After it stalled I finally got it to crank again (keep in mind, the temp readings are fine, so my husband is on the phone telling me to keep trying). It cranks, valves begin to rattle like a cummins, so I shut it down.My Durango came home on a car trailer after the top radiator hose blew off after cooling down, filling up with water, and trying to limp home. (How shameful to have a Ford pull home my baby).

Here's what we've done. We've replaced the thermostat and the clutch fan. Drained and replaced all coolant with 50/50 mix. It's running hot now for my husband, a mechanic, and other mechanics. The computer is not giving any codes other than one that basically says my gas cap is not tight. Thecoolant mixtureis flowing freely. They had to release the air in the radiator about 50 times to get it all out, so that's been done. Infared shows bottom hose is reading at 190 degreesand top hose is running 230. So, any suggestions? I would take it to a dealership, but my brother-n-law has borrowed my spare car, and he too brought it back on a car hauler after tearing it up. I need to find the problem so I can buy the parts tomorrow before everything is closed for the Holidays.

Thanks a bunch!
Ang

 

I forgot to note that when I would hit 80+ mph, the truck would begin to cool off. That's one reasonI thought it was the fan.

Ang

 

I'm thinking you should take that IR thermometer and hit the radiator fins all over to see if there are any obstructions in the radiator. There may be scale buildup in the cooling lines in the radiator. The biggest issue with overheating in the 4.7's is making sure the system is completely bled but I guess you addressed that. You may also want to check your oil level since it not only lubes but cools the engine.

 

Ang:

From the sounds of it, you have done quite a bit of parts swapping. At least you "should" be able to rule out those items. As Mean Green says,I would now turn my attention to the radiator. Sounds like it could be partially clogged. Another possibility (expensive) would be a leaking headgasket allowing hot combustion gases into the cooling system. As many times as it has overheated, I would not be surprised if you have warped a head, and the leaking gasket will then soon follow.

Hopefully this is not the case. Getting the air bled out is very important. I have found that leaving the bleed screw located on the upper hose out while idling it, and topping off as necessary via the hose entrance works good for me. Also, during this process have the heater on full bore, and run the rpms up to 1.5-2k several times to help the air out.

Then, put the cap on and take her for a good 2-3 mile spin. Return home and after a little colling off, remove the cap and top off again if needed.



Don

 

The fan doesn'thelp coolingabove 20-30 MPH. Kind of odd that it cools better at 80 than lower highway speeds, though. Flow restrictions usually present more at interstate speeds than in town; even though you're flowing much more air, you're also working the engine a lot harder at 80 than 50. I've had plenty of customer cars that would hover in the normal heat range around town, but get out on I-25 and try to run 80-90 and they would peg the temp gauge in short order. Every one of those was a restricted radiator (or restricted airflow throughthe radiator)or head gasket. The ones that overheat in town but not on the highway are almost always fan clutches or electric fans that fail to come on.

A thermostat stuck closed, failed water pumpor badly clogged radiator will cause overheating no matter what the driving condition, even in freezing temperatures.

A thermostat stuck open can go either way, depending on many factors. But on newer cars with their smaller radiators, coolant flowing that freely can cause overheating, as the coolant passes through the engine to fast toabsorb the heat. The temp gauge will read cooler than normal, but the engine itself is running hot. Older cars with big 3 and 4 row radiators tend to run too cold with stuck open (or removed) thermostats. A thermostat stuck open on a modern OBDII vehicle will usually throw a code becasue the engine does not reach a certain temperature in a certain amount of time.

You need to do a block test to check the head gaskets/heads. If it passes, I'd go with a Radiator. If not, the heads are comin' off to be pressure tested and then milled for reinstallation.

BTW, head gasket failure can cause overheating without coolant consumption; the breach is too small for coolant to get into the combustion chambers under themaximum 15-17 PSI of the cooling system, but gasses can easily get out under the thousands of pounds of pressure generating during combustion. As these gasses enter the cooling system, theypush coolant out into the reservior and createa similarconditiontoair in the system, but worse, as the gasses are constantly pushing coolant away from the area that most needs it. The aforementioned block test is done with a vented bottle that you fill partially with a blue fluid that turns yellow when it comes into contact with hydrocarbons. But beware; small leaks sometimes do not show up on these block tests, but wil still cause overheating. A gas analyzer is effective in finding these very small leaks. I've had more than one Subaru that passed a fluid block test, but failed with a spectrometer.

 

Here's what we've done thus far:

2 new thermostats
1 new upper radiator hose
radiator flushed
new waterpump
new fan clutch
1 can bars leak gasket seal
C02 chemical test to check for cracked head/block/gasket came back negative on the damage
compression test dropped about 1/4 pound, which is normal I was told
Infared temp check on (temp in top hose 220 and temp in bottom hose is 190)

Now after adding the bars leak, I drove it, and it didn't run hot until I got almost homefrom shopping. Less than a mile from home it shot up and I pulled over. BIG PROBLEM! However, after I sat awhile and restarted it, instead of climbing back up as I drove it, the temp began to fall. Now I have water in my oil. The good news is that this thing has cast iron heads, so the chances of the head cracking are smaller than with aluminum heads. Since thepet **** (why do mechanical engineers come up with such funny names) would not open we weren't sure if we ever drained everything off right and perhaps the bars leak didn't work. The bars leak we used did not have liquid glass, aka sodium silicate, in it, so that maybe why it did not seal up. My husband is a mechanic, but he's had it, so off to my other mechanic it goes. My mechanic believes it's a busted head gasket, but I'm saying it's the intake gasket. What do you guys think?

Ang

 

Ang;

The 4.7 engines do have aluminum heads. It is the older 5.2/5.9 engines that have the cast iron heads. Although the 4.7 engine is not known for intake gasket issues like the 5.2/5.9, that does not mean it can't happen.

Water or coolant in the oil is not a good sign. Bearings and antifreeze are not at home together one bit. The intake has to come off to get the heads off. I would start there and you just might be right. Hopefully all of the overheating has not warped the heads.

I think you can have a dye put into thecoolant to help find the leak.

Sorry you are having this bad luck. My 4.7 has been pretty much flawless for all of its 66k.

Don

 

N8, you maybe right about them being aluminum, but when I first started running hot, the mechanic (another relative) who came to get me said they were cast iron heads. Then when I looked up the heads online to see about buying new ones instead of sending these to cylinder head and exchange (our only local head shop) I found both listed online for the the 4.7 engine.

Ang