Correct Thermostat Temp

[Steve in IL]

1973 Ford 4000 SU Gas (3 cyl). What do you experts say is the correct thermostat for this tractor? Online sources vary from 168 - 188 degrees F. Thanks.

 

[Sean in PA]

Depends on what climate the tractor will be used in. If it will be used in a normally hot environment go with the 168 degree thermostat. If it is in a northern, normally cool/cold environment, go with the 188. If somewhere in between go with the 172.

If it was a diesel I would say to go with the 188 in all cases as the diesels run cooler and need to get up to temperature and worked hard to perform at their best.

 

[Bern]

Hotter is always better in my opinion. A 188 thermostat is open just as far as a 168 thermostat at 212 degrees, which is the point at which I start to take notice of my temp gauge.

 

[Texasmark1]

I have 3 Ford diesels. The two older ones have 168 and the newest I installed a 188, reason being is that it gets used in the winter and I want it to get warmed up without me having to wait or putting cardboard in front of the radiator. It's a weather related thing with me anyway.

On the 3000, which has the same instrument panel as the newest, 3910, the 168 puts the needle midsection of the white area when it opens. The 188 puts it at the intersection of the white and red area (about midway of the meter) where it stays once it opens.

 

[docmirror]

There are a couple concerns. The only reason to go hotter is thermodynamic efficiency(That's why modern cars have 203F or so thermostats). Of course a 40 YO tractor is not a modern car, which means thermodynamic efficiency isn't really a concern. That would argue for a cold thermostat due to better wear control.

However, a cooler engine has a bit higher mechanical resistance. This would be an issue if the engine was a tightly built as a 2009 Ferrari V-12. Of course, it's not, so no worries on having a too tight engine that cold.

I would opt for the 168 or a 172F, as this was common back in the 60s/70s. But - with this temp, and loose engine, one needs to maintain a good oil film, so make sure to get an oil of 30W or so when at temp. Modern thin oils just won't hold the film. I would also argue against a very wide spread multi-vis as the additives to change the molecular structure during temp change can affect the shear properties.

 

[Texasmark1]

Before the popularity of synthetics, I picked up on comments supporting what you said comparing 10-30 to 10-40....comment paralleled your comment
about additives to reach that far, limited the lube properties.

In comes synthetics and that went out the window, like the T6 Rot 5w-40 C rating I use in my newer tractors. On thin oils and today's engines with their
tight tolerances, I had a 2009 Ram Hemi 8-4-8 and owner's manual stated that if I didn't use 5w-20 the system wouldn't work and stated that the oil
pump was designed for that weight oil. Feeding that to a 15w-40 C and S rated, heavy oil guy all his life, was a hard pill to swallow, but the engine didn't
stop running....quite the contrary!