A few days ago, when entering the highway from a dead stop, I had a sudden overheating message when accerating to make use of a small gap. Funny enough, this was the first time I went full-throttle on the truck since purchasing in the spring. It was met with an overheating message, a topped-out coolant temperature guage, and a ****-ton of steam in the mirror. I pulled over and opened the hood to find coolant all over the engine bay. I hate the smell of coolant. It appeared to have come from the reservoir cap. The truck was off, but the coolant in the resevoir was still bubling. I limped home, stopping and shutting down everytime the temperature guage approached the redline. During this time, I was running the heater with the windows down to try and pull heat from the engine. I noticed the heater got weak after a bit, and was blowing cold by the time I got home. This lead me to suspect a bad water pump, specifically the impeller. Between the pressure cap, thermostat, and water pump, only a pump with damaged impellers would explain overheating with a cold heater core. It appeared that coolant was not flowing as it should.

Today I'm off work, so I started taking the cooling system apart.... my guess was correct, and I was hoping I was wrong. My impeller had exploded into several pieces, meaning coolant flow came to a screeching halt. My theory is the cheap plastic impeller was weakened with time and heat cycles, and at nearly redline RPM was too much centrifugal force. I rarely go above 2,000 RPM, so who knows how long this ticking time bomb has been around.

Luckily, all the pieces seem to be accounted for after recontructing the impeller like an expensive puzzle. Here's a picture of what I found.


I'm not trusting another water pump with a plastic impeller after this incident, so I ordered this one with a cast-iron impeller from RockAuto. While I have half my cooling system on my workbench, it's also a great time to replace the thermostat with an OEM Motorcraft 190°F (stock temperature to start opening), a new coolant cap, and some new coolant. Thermostats and coolant pressure caps are usually considered maintenance items, and should be replaced every so often, so this would be a good time. Half of the draining coolant missed my bucket, but I've been wanting to replace it anyways. I used a garden hose to flush old coolant out, so a flush with distilled water and a coolant fill should be pretty quick when the parts arrive in two days.

I absolutley hate that car companies are making so much crap out of plastic. It doesn't age well, and it's not strong. Plastic fasteners and plastic stress-bearing parts have cost me a lot of money and time over the years.

 

You're repairing yourself or take to a shop?

I think I have a bearing going on the belt tensioner at about 160,000 miles.

Thought I might replace the water pump at the same time.

Having some issues with my local Ford dealer, & he is telling me there is a secondary, internal water pump on my 2018 F150.

I priced parts from him, to replace it myself, but considering getting parts elsewhere.

I told him, as far as I know the water pump is all external on 2018 3.5 ecoboost, and he still says there is a secondary internal pump behind the timing chain cover.

I don't have any coolant issues, and do regular oil analysis to watch for any signs of coolant in oil.

I am considering ordering parts from another Ford dealer if he is giving me inaccurate information. They do have my serial number on file for previous warranty covered work.

I understand there is a vacuum refill procedure. Has anyone used vacuum assist (Shop Vac) somehow to do it yourself? I think I should be able to create vacuum at he degas bottle and suction refill from the bottom drain hose, sucking new coolant in.

 

It's not really a water pump but Ford does call it one. It's more of a support/feed plate.

 

I do all my own work, with the exception of tires and alignments. I don't have the equipment to properly balance or align tires, and I've grown fond of Discount Tire after working for them in my late teenage years.

The whole fix was pretty simple and quick. The ecoboost you have seems a bit harder. Also, I'm a big fan of RockAuto for parts.