Testing new thermostat
 

Bought a new Robertshaw thermostat BRA-330-180 for my 66 GTO engine rebuild. Decided to test it before installing it. Suspended it in a pan of water and made sure it was not touching the pan anywhere. Watched the meat thermometer climb up to 160, then 170,then 180, but never saw anything on the thermostat move. Temp kept climbing to 210, but still no movement on thermostat. I’ve never done this test, so wasn’t really sure what to look for. I was looking down at side B as the temp climbed. Side A was facing the bottom of the pan so I could not see what was happening with it. Is this thermostat a dud, or is this a case of operator error? What should I be looking for to confirm it is opening at 180 degrees

Need ro measure temperature at the same level as the stat, the temperature will vary by depth. I use a k type thermocouple for experiments like this. The rated temperature is where the stat will start to open, the bimetallic spring moves the plunger. You will see it when it moves.

A 180 stat will start to open at about 183 and be fully open close a tad above 200.

I find it best to use a thermal gun and once the water starts to make small bubbles turn off the heat and remove the pot from the stove, then with the gun watch until the temp gets down to 205 and only then drop the stat in.

It’s best also to do this test in a large volume of water so the temp drops slowly before you drop the stat in.

I prefer the conventional spring-type stats, less of a chance to hang.

Not sure why they call that type 'high flow', seems to me it would flow less than the spring type. But may just be the way my brain works.

Conventional spring type you certainly can see them open and close, with ease.

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Thermostats
 

Had good luck with Superstats years ago.
Been doing NOS ones off eBay and very impressed.
Years ago picked up a NOS AC Delco 170 for a corvette.
When tested it cracked open at 167 and fully open by 185.
When in use my gauge stays at 170ish around town and175ish
On highway in the heat. Drops right back to 170 when back
On side roads. Bought another as a spare for garage art.
This is with a standard duty fan clutch!!!

Gerry

Get the stainless steel type from Napa, Much better Stat in my opinion. https://www.napacanada.com/en/p/THE1600025

Those look nice. What temps are they offered in?


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I test all of mine s well - looking at side A is better to tell when it begins to open.

Me also on the flow.
My engineer dad would always test them in a pot of hot water when he thought that was the issue

Testing new thermostat
 

Dug out the original 195 unit that was in the engine previously to test it and get a better idea of how to recognize when it was opening. It still works fine and the opening and closing events were obvious. Bought the 180 Napa stainless steel version and tested it with my infrared thermometer instead of the meat thermometer used previously and it worked just fine. Tried the infrared on the Robertshaw a couple more times, but I swear I can’t detect that any movement occurs even up to 220 . Makes me very reluctant to use it, so I guess I now have another piece of garage wall art to hang up.

Last month, I changed my upper radiator hose when I noticed the thermostat looked strange in the housing. One of the thermostat tangs separated from its body. Fortunately, It stayed partially opened and I avoided overheating.

I tested all my old 180° and 195° thermostats for a replacement candidate. The old Robertshaw ones still worked great but the OEM style versions did not open even in a good boil. The 180° thermostats started opening at 160-170° while the 195° thermostats opened at 185-189°. Compare these measurements to the attached table.

I was surprised that I had an original HRD stamped thermostat. It was one of the bad ones.

It's a MotoRad 5200-160. MotoRad stamped on the side

Yes, your right. Thanks for pointing that out. You can just barley see it stamped on the side of thermostat. I just went in garage and grabbed one of my old ones from Napa. Looks like they have change to different suppliers. Anything that was any good is gone.. Dam.
These have been the ones I've always used. Made in USA. Just found this. MotoRad (Stant was acquired by MotoRad) https://www.youtube.com/watch?v=KCS95D9FOPY

Shows this on Amazon. Made by Motorad. Says Stant in the Title. Shows USA on the Stat. Then is listed made in China. unreal.
https://www.amazon.ca/Stant-45356-Su...0&gad_source=1