2000 Windstar Temp Gauge

[roygolf]

Question:
I have a 2000 Ford Windstar w/106,000 miles. No major problems in the past that was not covered under warranty. In the last two days, I have noticed the temperature gauge bouncing up and down while driving. It will slowly rise up and all of a sudden drop back to "normal". I have also noticed that it takes the heater a longer time to get warm. Could this be related and if so, what is causing the temp gauge to bounce around so much? Any help is appreciated.

[phil-l]

I recently had a similar problem on my 2000 Windstar LX 3.8: This symptom is almost always caused by a failed engine coolant thermostat.

The thermostat is just under the throttle body. It's not a difficult do-it-yourself job. This is also a good opportunity to replace the engine coolant. Search for "thermostat" on this forum and you'll find more useful information.

[wiswind]

I took pictures of the replacement of the thermostat on my 1996 3.8L windstar.....
Should be similar to yours...but buy the parts for your year......

http://community.webshots.com/album/201931518cScpNK

[Mackab]

Overheating at highway speeds is a telltale sign of a thermostat stuck open.

[phil-l]

Mackab -

No. A stuck *open* thermostat *over*-cools the engine. The thermostat should open and close to keep the engine at a constant temperature. A thermostat that's stuck open all the time keeps the engine cooler than it should be. Most stuck-open thermostats aren't noticed until cooler weather, when heater performance suffers (the engine is so cool at the heater doesn't have much excess engine heat for the interior).

[Mackab]

From Tim Giles Automotive Service Manual 2nd edition. " A stuck thermostat will cause an engine to overheat or to not heat enough. If it is stuck partially OPEN, the engine can overheat on highway trips and not warm up as soon as it should in town."

[phil-l]

Mackab -

One crucial word missing from your orignal comment: "partially". A thermostat that's only allowing partial coolant flow has the potential to cause overheating in any situation. At that point, highway driving vs. any other driving likely becomes irrelevant; not enough coolant can flow.

Thankfully, many (if not most) thermostats are designed to fail completely "open", avoiding risk of overheating.

My 2000 Windstar LX 3.8's thermostat intermittently stuck open just a few weeks ago; I experienced symptoms similar to roygolf. On the highway, the temperature needle would sometimes remain at the lowest setting; never even close to warming up. Heater performance was awful. Replacing the thermostat solved the problem. Obviously, the thermostat was stuck all the way open, not partially.