My wife has a 1999 with 3.0. wit 165k miles. Lately we have noticed it will start to over heat and fill the overflow with coolant ( and even puke it out some) but only under a heavier than normal load. We have a small mountain pass (4 miles up hill) that we have gone over twice and it did it both times. Normal around town driving even in the 100 degree weather it's fine even with the A/C on max.
T-stat is only a few months old
Coolant was flushed at time of T-stat
Not sue the age of the water pump or if it has ever been replaced.
Hard to see but looks like good flow through the radiator.

Could it be the fan clutch? I was thinking that even under heavy load and going 65 MPH there should be enough air flow through the radiator but am i wrong?
Not sure what else to look for.

 

Fan clutch yes...next time it heats up pull over and pull the hood give engine a little rpm the fan should kick in blowing air through radiator...... you can always put the heater on full blast to get rid of some heat.... open windows...

 

Going to try this today. The more I think about i the more it could be the fan clutch. I'm going to put a new T-stat first just because it's an inexpensive thing to try. I have seen them fail or partially fail in a very short time. New T-stat and then take it for a drive up the mountain.

 

Also after a drive when engine is hot feel the upper and then lower radiator hose, lower should only be about 20deg cooler, not cold

Start engine, still warm/hot
Have someone REV engine and hold it at about 2,500RPM
Squeeze upper rad hose and then squeeze lower hose
If lower hose is easier to squeeze and much cooler then radiator is clogged up, replace it


Generally a failing fan clutch will cause overheating when stopped or driving slowly
The fan is there to pull air thru radiator and circulate air in the engine bay
When you are driving above 35mph the vehicles speed is providing more air flow thru the radiator than any fan could


Funny story
Years ago I was driving across Nebraska in an old chevy impala, the big boat style, lol
Had the window rolled down and at 60mph I could barely feel a breeze, stuck my arm out and it was like no wind at all, I thought that was very cool
Then looked at the temp gauge.................it was heading UP and pretty fast, pulled over thinking I had lost coolant or ???
Got out and there was now a very strong breeze, then it dawned on me, tail wind so no air through the radiator
Opened the hood and cooling system was fine
Set back off but at 45mph, so less load on the engine and temp was warmer but not hot, wind speed died down after an hour or so, so back to 65mph

 

Good story! I'm from Nebraska so I know what you mean!
I have a Fluke infrared temp gun and can check top and bottom temps today too.
Thanks for the advice so far!

 

UPDATE
Replaced the T-stat and every hose. Drove up the mountain with A/C on and no issues. Thought the problem was fixed!! Wrong Yesterday drove less than 3 miles to the store and parked. Got out and saw coolant leaking. Opened the hood to find the reservoir overflowing. The upper and lower hoses were under a lot of pressure but only warm to the touch.
I went in to the store and let the truck sit for about 45 min. Drove home and when I got home the reservoir was back to normal (Sucked back into the radiator) and hoses felt like normal.
I was thinking head gasket but wouldn't it have the symptoms all the time? The truck was driven a few short trips normal and then this happened. Then back to normal.
I am going to do a compression test and the glove test but looking for other possibilities. To me it acts like a sticking T-stat but this is a new one. (Although new doesn't mean good!)

 

Sounds like you did not get all the air out of the system after hose replacement etc.... did you run the engine to normal temp/stat open before fitting rad cap.... running at idle cold engine you can feel the stat housing getting hot as the coolant flows through the top hose.. then again could be head gasket...... after the engine is normal temp before fitting rad cap is there any air coming to top of radiator,after taking rpm to 1500 rpm or so

 

I did let it run until the t-stat opened. Then topped it off but it didn't take much. Do you think I could have had an air pocket still? Then it finally worked it's way out?

 

If the cooling system has no air in it you should be fine, leave heater controls on hot so the water flows through system... on the other hand if the top radiator is rock hard on warm up and pushing air into overflow you got problems

 

I'll try some things.
It has not been this way before. This is the first time I have felt the hoses rock hard but only warm to the touch and on a very short drive. The confusing part is after the drive home they felt normal and hot to the touch. I'm hoping it was an air pocket.

 

So far this appears that I just didn't get all the air out. I checked a few things. Did the glove test, and everything seems ok. The only thing I see is maybe I have a temp tending unit going bad.

 

Best way, I have found, to refill cooling system is to disconnected heater hose that connects to intake manifold, at the heater core end
Refill
This lets all the air flow out of the heads
When coolant starts to come out of the hose and heater core, reconnect hose

 

Next time I will definitely do it this way

 

ANOTHER UPDATE!!

The other day we pulled a small trailer with junk (total weight was probably 700 lbs) up and over the mountain with no issues. Yesterday the truck was driven just a few miles on level ground and it started to overheat. You could hear it "Boiling over".

It has been driven several times so I don't think it could still be any kind of air pocket in the system. I guess I could be wrong though.

Glove test shows no movement at all. Fan clutch is nice and tight.
Could it be a water pump issue? Possible defective T-Stat?
I've never had these issues and I've replaced many thermostats over the years and drained and filled many cooling systems.

 

When it was boiling over did you pull the hood and give it some throttle, was the fan blowing at full speed... was the top hose hot to the touch... was temp gauge pegged......... pulling over mountain the revs must have been over 3k spinning the fan clutch fast.......... then again the new stat could be defective...... only thing making the cooling system work is ..water pump...radiator...fan clutch...stat..... on a worse note which i doubt if the head gasket was pushing air into the cooling system........... when it was boiling was the coolant getting pushed into overflow container

 

The fan was definitely pulling air
I didn't check the hoses but the first time it happened both were under pressure but not as hot as I expected.
The gauge read normal ( But it has acted weird so the sender may be bad)
Going over mountain it was actually bogged down. For some reason it would not down shift on it's own. (That's a different issue I will look into later)
The coolant was being pushed into the overflow tank. (Also has another new Radiator cap)
I've done the glove test to check for head gasket and the glove does not move at all

 

I read on another thread here that if the coolant overflow tank lid gets popped off it is a sign of head gaskets. Is this true? Mine does this sometimes but passes the glove test. When it pops the overflow tank cap off I hear it bubbling / boiling over. I let it sit for a few minuets and then it runs great again.

Could a water pump with a failing impeller cause the same issues?

 

Combustion gasses in the cooling system ? then the pressure must be higher than the cap pressure to blow it into overflow tank...... does the overflow tank fill all the way to the top with coolant and spill over, if so you got a cracked head/gasket............. the only way to tell is to use the combustion leak indicating fluid tester... tapered fluid applicator fits into radiator cap hole with coolant 2'' below .. running engine at idle.... if fluid color changes you have above problem..... Question where are you fitting the glove test radiator or overflow tank.
If your just getting bubbles of air into overflow, they have to be coming from the head gasket etc........ water pump.. only way to tell is to pull the heater hose off at heater core, the one from the pump...cold engine.... get someone to start engine coolant should gush out of that hose if pump is ok..

 

Thanks for all the replies and help. Even though it passed the glove test it did not pass the chemical liquid test! It is exhaust gasses in the cooling system. Looks like its head gasket time.

 

Bet its a cracked head.............

 

Head gaskets just don't fail on their own for no reason, something caused it to fail, like Sparky said, a cracked head.
You also have to find out what caused it to over heat in the first place and caused the head to crack, assuming that's the actual problem.
You'll find out once you get in there.

EDIT:
When it's over heating, is the rad hot all over, or if you feel it, are there cold spots on the matrix _ cold spots indicate a partially blocked rad ?
All these problems stem from a partially blocked rad, and/or a water pump where the impellers are corroded away.

 

A hose popped off a few months ago and it overheated. It didnt start showing signs until we did all the hoses and t stat. So I do know what caused it.

 

That would do it, the over heating crushes the head gasket and breaks the seal.
I would get the heads tested for warpage and cracks too, especially warpage, it only takes a machine shop a second with a straight edge.

The head gasket can seal up to 5 thou, a human hair is around 3 to 4 thou.

Also with 165k, you may want to consider a valve job.

 

I found a set of new heads. And I'll also get a full Felpro gasket set and new head bolts and water pump. Anything else you guys think would be good to replace?

 

You may want to consider replacing the timing chain cover gasket, if it's not leaking now, they usually do eventually, assuming that someone hasn't already replaced it.
Get a Ford water pump, the aftermarket ones are hit or miss, they may last for years or fail just outside the warranty.
Sometimes they fail with in the warranty, but then you have to do it all over again.

When removing the timing cover, don't damage the oil pan gasket.

Don't forget the front crank seal if you do the timing cover.

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