How to: Replace a thermostat on a 2000 4.0L SOHC V6 | Page 2 | Ford Explorer Forums - Serious Explorations

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How to: Replace a thermostat on a 2000 4.0L SOHC V6

Thanks for this write up! I just got done replacing the thermostat on my 2000 EB 4WD. Piece of cake with all your photos!

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replacement thermostats and upper housing leaks

So around a year or 2 ago the water pump gave out and I replaced it. I had problems with leaks and figured it was the water pump but turned out that the lower thermostat housing was deteriorating. I replaced that and hoses and everything was fine. Last weekend coolant started spraying everywhere and I found the house going from the housing to the heater burst. The thermostat (new one from the replacement Dorman housing) wasn't opening and caused the overheating. I picked up a new thermostat and then the hose. The flange on the outside edge of after market thermostat is half of the size of the Dorman thermostat. I'm having all kinds of issues with leaking at the seam of the lower and upper housing. I'm not sure if I am tightening the upper housing to the lower housing too tight. We made an aluminum spacer but that is not helping either. We took a look at the upper housing and it appears to be warped. I picked up a new one and am hoping to install it here in a few minutes. I have also replaced both of the 13 year old temp sensor/sending unit

Any other suggestions? I had used the old gasket and the new gasket before trying the custom made spacer and that worked the best so far but still was leaking. I'm wondering if I could find a larger in diameter gasket...

2000 Explorer 10/99 up to 283k miles

*** as an update the upper water outlet housing was warped. Replaced with new and tightened down a little at a time and tested leaking before I had it tightened down all the way. So far so good 10/4/12.

The following write up is for informational purposes only. This is just an account of what I did while troubleshooting an overheating anomaly (see thread here) on my 2000 Explorer Limited. As part of my T/S I removed the thermostat and took some notes and pictures along the way. I was not sure how involved this was going to be but it end up been very straightforward. It took me about 1.5 hours total to do this and another 15 minutes or so to test drive the Ex. Here is what I did:

Please note that this write up is for the removal and replacement of the thermostat for a 4.0L SOHC. The write up for the 4.0L OVH was done by 'Charlie' and can be found here.

Tools needed:
-8mm socket
-10mm socket
-9/32" socket (the 7mm was a bit smaller and the 8mm to big)
-Paper towels or rag
-Small brush to scrape off some gunk and debris

First off, when I checked the repair manual, it said to drain the coolant out of the car. I did not have to do that. Since the thermostat sat on top of the block I thought that if there was some coolant it would be the coolant inside the upper hose, and that it would be minimal. So, I decided to go on very carefully without draining the coolant.

With the engine cool, using a ratchet and a 9/32" socket, I removed the four screws holding the plastic engine cover in place.

Next, using an 8mm socket, I loosened the clamp holding the air filter duct enough to be able to slide it off the intake body. After removing the electrical connector, and the two hoses that connected to it I removed the air filter duct from the Ex.




Using a 10mm socket I removed the top wire from the alternator (not sure if that is the ground or current and I did not check). I did this to get better access to the thermostat housing and the upper hose clamp. I also found it easier to work when I removed the electrical connector from the intake body.

Using a pair of pliers, I moved the clamp holding the upper hose to the thermostat housing out of the way. To move the hose out of the way I removed the 8mm screw that hold the hard plastic section of the hose to the engine block.

With everything out of the way there is now enough area to remove the three (3) 8mm screws that secure the thermostat housing. Note that there are only three screws and not four like I thought. Removing the housing cover give you direct access to the thermostat. To remove it just pull on it. I think I've read t that it is a good idea to notice the orientation of the thermostat and to install the new one in the same position. I am not sure about that but I did it anyway.


Before installing the new thermostat and gasket, using a couple of paper towels and a small brush, I cleaned both sides of the housing to remove gunk and loose debris. From the pic below you can see the discoloration from coolant that may have leaked from the hose or the housing.

Once the new thermostat and gasket was in place I re-installed everything in reverse order. Bleed (burp) the air out off the system and fill with coolant/water as needed.

Below is a pic of the old thermostat (left) and the new one (right). After a quick visual inspection I could not tell if he old thermostat was bad. One difference between both thermostats was the temp rating stamped on them. The old one (DFT) was rated to 197/223 degrees Fahrenheit versus 190/??? degrees for the new one (Stant, P/N 13649).

Ooooh, I'm glad I found this! My Green Beast has started to have some overheating issues (not bad for a 13-year old) and this is something I will have to try.

The write up and pictures are amazing really help with changing my thermostat on my 2005 Ford Exp sport tract. It's great to have a forum where every one is willing to help others out with there issues and give such detail on how to do repairs. This is truly a great site to be part of just wanted to thank every one for the help and assistance I have received from this site.

Thermostat and AC are connected

First I found this post very helpful in replacing my 2000 Explorer 6 Cyl thermostat. My first indication that the thermostat was bad was when the AC stopped working. In Texas in July that's a serious problem. It turns out that when the engine temp reaches a certain point the computer shuts off the AC.
I found this out after having a leaky AC hose replaced and Freon added but by the time I had driver around more that 15 minutes the AC stopped working again. Replaced the thermostat and problem solved.

I did mine like Racingtheburg did. Couldn't get to all three screws with the tools I had available with the throttle body and upper intake in place, so off they came. I, too, like the idea of "flagging" with tape, but opted not to this time - everything pretty well laid in place, waiting for me to get back to it. Bar422 - after disconnecting all the hoses and electrical connectors from your upper intake, look down at the front of it - you'll see maybe 5 or 6 screws holding it to the lower. These screws are "mirrored" in the back of the upper, so a total of 10 or 12 screws. When you've got them all out, the upper portion lifts off from the lower. Could take a little GENTLE persuasion. And, yes, the screws in the very back ARE tricky little devils. In retrospect, perhaps a 1/4"-drive 8mm swivel socket would have made it unnecessary to remove the upper intake... Oh well, we live and learn. Chris:us:

When I did the t-stat on our 99 Sport 4.0 SOHC I removed the throttle body to make it a little easier to access the t-stat housing bolts.