How To Replace the Upper and Lower Thermostat Housing on a Ford 4.0L V6 SOHC Engine

Steps 11-13: Refill, Check, Finish

Step 11: Refill Coolant System

Now you need to refill the coolant system. If the coolant still looks good, you can reuse what you took out. Remove the radiator cap, get a funnel, and pour it in. If you're using new coolant, use a 50/50 coolant/water mix and fill it up through the radiator cap hole. Fill it right up to the top. Then add coolant to the coolant expansion tank up to the cold fill line.

Step 12: Check for Leaks and Adjust Coolant Level

Start the truck up and watch for leaks. Get a good flashlight and look around the base of the lower housing. Then check all other connections to the housing (heater hose, upper radiator hose, sensors). Turn the throttle faster and check again. Look underneath to see if you see any coolant dripping. Don't be confused by coolant that might already be there from your previous leak (I had coolant all over everything at this point).

Turn the heater temperature to maximum and the fan speed to maximum. Direct the air to come out of the upper (A/C) vents. Then take the truck for a spin and get it up to operating temperature. Feel for hot air coming from the vents. Watch your water temperature gauge to make sure it rises to midway but not beyond.

If you have hot air coming from the vents and the temp gauge looks good, then return home, but leave the engine idling and open the hood. Feel the upper radiator hose to see if it's hot to the touch. If the hose is hot, then everything is good. If the heater air isn't hot, the temp gauge doesn't come up (or goes too high), or the upper hose isn't hot, then you probably don't have enough coolant in the system. Shut it down and let it cool, and then fill it up again.

Even if everything looks good, you'll need to continue adding coolant to the system over the next couple days. Each morning before driving, and when the engine is cool, check the level and add coolant to the radiator and coolant expansion tank. It is normal for it to take more over the next several uses as it bleeds the air out of the system. It took me about two days until it was finally full when I checked it. Remember to only add coolant when it is cool!

Step 13: Enjoy!

Keep an eye on your water temperature gauge over the next couple days. Continue to watch for leaks too. Treat yourself to a car wash with an underbody spray to clean off all that old coolant that got splashed all over everything. Remember that it may take a few days for any coolant you don't catch to burn off or evaporate, so you may still smell it for a while. That gross smell went away for me in about three days.

Once you're sure you have no leaks, reinstall the accelerator control splash shield (the "4.0L SOHC" cover).

I don't know how much your local mechanic would charge, but readers have reported estimates from their mechanics as high as $1500 (the average seems to run about $1000). So cngratulate yourself on saving the money, and knowing that the job was done right! Most of all, enjoy a leak free engine!

About Me

My name is Ben Grosser. I like to do things myself whenever I can. I also like to share information like this with others so that they can learn from my experience. One of my most popular pages is a site on how to build your own artist's easel. I have benefitted from so many people on the internet over the years who have taken the time to help others for free. I do this to pass on that help.

A few people have asked if they could get me a gift to show their appreciation for my work here. If you're so inclined I would certainly appreciate anything from my Amazon Wish List! But of course I wouldn't expect it.

If you have any questions, or any suggestions to add, please . I would also love to hear from you if you use this information and it helps you out.

Next -> Drive!

this site was written by ben grosser
all content and photos are © 2012 and may not be used without permission.