The T-Stat that Fred is looking at from Improved provides a 100% flow through the cooler when fully opened. In the full off condition there is still something like a 10% flow through the cooler. The image below illustrates the operation better than I explain it;
Failure in the full on condition would maintain very cool
oil and failure in the full off condition would still provide for some level of cooling from the
oil cooler.
In the end there is no substitute for paying attention to the good looking gauges on our dashboards however if you're the forgetful type you can always build a flashing light circuit or buzzer circuit to draw your attention to a T-Stat failure.
If you want to get real fancy you can build in a warm up circuit that does not trigger the alarm until some point in time you feel is appropriate i.e. up to temperature or some amount of running time etc.
Most of the SetRab
oil coolers we use, w/o a T-Stat, will over cool the oil for the typical replica. It may be a small cooler but it has prodigious cooling capability..
Ed