Checking thermostat on my Explorer

[cober]

When my thermostat was acting strange I decided to test it and here is is:

 

[poker4me007]

The only problem with that test is your coolant should never get that hot to where it boils...So if its a 195 thermostat it still may not open at 195 degrees...

 

[koda2000]

Besides the possibly damaging the t-stat if the water is too hot, I'd never go through the trouble of removing a t-stat w/out replacing it. Especially if I suspected it of malfunctioning.

 

[poker4me007]

Besides the possibly damaging the t-stat if the water is too hot, I'd never go through the trouble of removing a t-stat w/out replacing it. Especially if I suspected it of malfunctioning.

Same here, there not that expensive and I wouldn't trust a thermostat after that test...

 

[XLTrunner]

Every time I replace a thermostat, I test the new one in water on the stove. I use the wifey's candy thermometer and bring the water up to around 195 degrees or so until I see it opening up to verify it's operable. Too many stories of new thermostats being defective out of the box.

 

[J_C]

I guess I'm too trusting, when I buy a new one I just assume it's going to work. I have thrown an old one in a pot to see and confirm that it did work, then put a new one in anyway.

I am doubtful that (non-pressurized so a max temp of about) 212F boiling water would damage a t-stat. That's less than 20F difference while the wax in the slug should have a boiling point hundreds of degrees higher. Plus, it seems an acceptable range in that manufacturers like Stant claim

The thermostat fully open about 15-20 degrees above its rated temperature

http://www.stant.com/index.php/english/products/consumer-products/thermostats/abcs-thermostats/

 

[koda2000]

I personally have encountered exactly one defective new t-stat in my many years of wrenching, but I know you can run into a bad one right out of the box. I don't bother testing them. They typically don't fail immediately, so running a hot water test on a new one isn't going to tell you much. They can still stick on you a week later.

 

[96eb96]

Stant Superstat fixed all the issues with this engine. The German one from Motorcraft will always run a bit cold. There are some TSBs about fluctuations and bypass hoses for the OHV, but they aren't made anymore.

I had 3 motorcraft stats and they always ran in the 1/4 range between 175-186 verified with a scan tool. Lowest it drops to now is 190. I don't think it will harm the engine but I don't like running cold, and my gas mileage went up, I take some very repeatable trips. If I run AC it runs at a steady 195. When A/C is on the heater core is bypassed, could have something to do with that.