14 Temp Spike

You can borrow a pressure tester a O'reilys for the cap but I would just throw a new cap and stat in there for starters.

Don Hall said:

Cooling is a simple equation. All that is needed is coolant flow, and air flow.
Stop one, or both, and you will experience overheating.

Your truck uses a closed cooling system. As the coolant heats, it expands, and
travels to the overflow bottle. When it cools, it reverses flow via a siphon back to the radiator. Outside air does not enter the 'closed' system. If it does, no siphon will occur, and the coolant level will keep getting lower.

How air enters the cooling system.....deformed cap gasket, loose/damaged connections, any unit failure/break in the system.

As mentioned, a properly working t-stat is important. A t-stat that only opens
partially, or not at all, will cause overheating. To check a t-stat, remove it, and
place it in boiling water to determine if it opens, or not.

Of course, the coolant must always be at the 'full' level. If continued filling is required, you need to check for leaks. A simple pressure test using a pump connected to the rad cap opening will detect any leaks. To check the block, the
t-stat must be removed.

Ensure the fans activate at the proper temps, check a maintenance manual for fan activation temps (I didn't see any temp numbers in my Owners Manual).

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Thank you for your explanation! That makes a lot of sense. Your response has been noted!

Update: After replacing the thermostat (Advanced Auto “premium” brand; no Ford OEM in stock - was looking for a quick fix) and driving the truck around the block, I was sitting in it typing this response. The temp gauge was dang-near on red, so I figured I’d shut it off. Once off, I noticed white fumes coming from the hood.

Attached is my best attempt at showing where the vaporized coolant is coming from - I believe it could be coming from the “gasket” between the hose/stat combo piece and the engine (if that even makes sense). In the first pic you can see a plastic or rubber nub sticking through the metal piece towards the upper left hand corner - that’s part of the “gasket” I’m talking about. Can this be a point of failure?

Clearly this isn’t normal. I also have zero heat in the cab, even when the AC is at 90 and the AC fans are on full blast. After the ride around the block and sitting in the truck for a minute, I was starting to get brief hints of warm air, but it quickly returned to cold/cool air.

Does this information help? My dad tossed in the idea of the water pump being bad, but I neglected to even look at it before coming in for the night.

Nice explanation, and photos, Joe. My '04 only has 19K miles on it, so I am not familiar with the engine compartment. I don't recognize a t-stat housing in the photos. I see the 'bulge' you reference, but I can't tell you what it is.

From your explanation: "driving the truck around the block, I was sitting in it typing this response. The temp gauge was dang-near on red". It would seem that the water pump could be your problem. Overheating in such a short drive indicates a lack of coolant flow. Fumes coming from the engine bay confirm that the temp gage is not the culprit.

The following is a link to diagnose a faulty water pump: https://www.yourmechanic.com/article/how-to-diagnose-a-faulty-water-pump-by-rocco-lovetere#:~:text=There are several safe ways to inspect if,for leaks. Step 6: Inspect the coolant reservoir.

That is just the shape of the gasket. Thermostats are critical on these modular engines, there is a top and bottom valve and they have to function well. The bottom part closes off another passage and needs to function right. I highly recommend you take it out and put a Motorcraft one in. I will see if I can find some diagrams on that.

I’d say either water pump and/or air in the system.

Have you verified both fans are operating and not just one?

Don Hall said:

Nice explanation, and photos, Joe. My '04 only has 19K miles on it, so I am not familiar with the engine compartment. I don't recognize a t-stat housing in the photos. I see the 'bulge' you reference, but I can't tell you what it is.

From your explanation: "driving the truck around the block, I was sitting in it typing this response. The temp gauge was dang-near on red". It would seem that the water pump could be your problem. Overheating in such a short drive indicates a lack of coolant flow. Fumes coming from the engine bay confirm that the temp gage is not the culprit.

The following is a link to diagnose a faulty water pump: https://www.yourmechanic.com/article/how-to-diagnose-a-faulty-water-pump-by-rocco-lovetere#:~:text=There are several safe ways to inspect if,for leaks. Step 6: Inspect the coolant reservoir.

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Thank you! I’ll read that soon. I wonder if replacing the water pump is something I can do in my own driveway.

07navi said:

That is just the shape of the gasket. Thermostats are critical on these modular engines, there is a top and bottom valve and they have to function well. The bottom part closes off another passage and needs to function right. I highly recommend you take it out and put a Motorcraft one in. I will see if I can find some diagrams on that.

Click to expand...

Please excuse my explanation or description, I was using that nub as a reference point for the particular “gasket.” It looks like the steam or vapor was coming from that location.

As for the Ford OEM thermostat, I figured as much. I will try to get my hands on one and hopefully I can return the “premium” brand thermostat.

Thank you all again for your help! I’d be stoked if I can fix this myself!

ExplorerTom said:

I’d say either water pump and/or air in the system.

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I saw that exact video not too long ago; that idea crossed my mind. I’ll certainly try whatever I can to not spend money.

JExpedition07 said:

Have you verified both fans are operating and not just one?

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Good question - in fact, I have not. I just assumed the jet engine noise meant both were functioning. I’ll check on that, as well.

Joe Public said:

Thank you! I’ll read that soon. I wonder if replacing the water pump is something I can do in my own driveway.




Please excuse my explanation or description, I was using that nub as a reference point for the particular “gasket.” It looks like the steam or vapor was coming from that location.

As for the Ford OEM thermostat, I figured as much. I will try to get my hands on one and hopefully I can return the “premium” brand thermostat.

Thank you all again for your help! I’d be stoked if I can fix this myself!

Click to expand...

That bottom passage has to work right or it will heat up, many aftermarket thermostats won't close it off right or at all.

Alright, update!

Today I replaced the thermostat (OEM), the water pump (OEM), the serpentine belt (I can’t remember the brand), and the radiator cap (Stant). In refilling the radiator, I burped the system, as well.
One or all of these, minus the belt, seems to have fixed the overheating/temp spike and restored heat in the cab. I still need to go out for an extended drive to make sure everything is good.

I might have a coolant leak, however. I’m not sure how much coolant is still hanging around in some nook or cranny underneath the car, but I can say there was a puddle underneath the car collecting/dripping from the transmission/close to the oil pan.

I also might have not refilled the system enough, therefore the plastic reservoir is depleting overtime - so this coupled with the old coolant under the truck could give the impression of a leak.

I have two more gallons of orange coolant that I’ll keep around for refilling the system.

Question: is adding extra coolant from the plastic reservoir ok? Or should I pull the radiator cap and fill from there?

Thank you EVERYONE for all of your recommendations, advice, and replies!