410 running too cool

Thor · #1 (**permalink**) 19-03-25, 02:45 PM

I would agree. Running at 55 is too low. The general rule is that you can't overcome the operation of a thermostat. The most common mistake is to fit a normal thermostat and then worry that the engine is too hot (generally it isn't) and then try to cool it with more fan power, which doesn't work because the thermostat always wins, it just closes a bit more.

In your case the thermostat must be sticking open, I think. It probably closes when the engine gets properly cold, but when it is just 25 degrees cooler than it should be the force is not enough to close it. Or maybe there is a significant by-pass route somewhere ?

I had heard that Stant is a maker of good quality thermostats, maybe track one of those down ?

David C · #2 (**permalink**) 19-03-25, 03:32 PM

I have been doing a little more reading and came across this, specifically for Chrysler engines:
http://www.allpar.com/fix/engines/co...tem-about.html
The internet being what it now is, it is possible to find articles supporting all sorts of alternative truths, but opinion does seem to be largely against running for prolonged periods much below 180F / 80C

Thor · #3 (**permalink**) 20-03-25, 04:12 PM

Yes, 80 would be a minimum, really. Maybe 75, but why ? 80 to 90 is fine and hotter is also OK if the system is pressurised.

David C · #4 (**permalink**) 22-03-25, 12:44 PM

I ordered a Stant thermostat but a MotoRad unit turned up. It seems MotoRad bought the Stant name in 2022. Forum opinion in the US seems to be that quality has suffered.

Nick Challacombe · #5 (**permalink**) 22-03-25, 07:20 PM

I drive a 1962 407 which as we all know was the first production V8.
I have had it 25 years and even when I bought it, it was known as a boiler.
The handbook suggest 90/100 as a running temp with a thermostat cap/ radiator pressure of 30 lbs sq in .
I cannot reach the facts as I am stuck in hospital so please forgive my memory.
The forum is essential reading! Thank you.

AndrewA · #6 (**permalink**) 22-03-25, 07:45 PM

Had a quick look on Summit website - there's quite a selection of thermostats across quite a wide price range. On a previous car I got through 3 thermostats before I got one that worked as it should. I guess you could try the old suspending thermostat in saucepan experiment to see what's going on but you may well have other things you'd rather be doing.
Hope it's sorted soon and glad car is running well. For what it's worth (and presuming temp gauge is accurate) I'm 80 to 90 most of the time - it might creep towards the 100 if I'm stationary for ages when it's warm weather but fans don't let it get any higher.
Cheers
Andrew

David C · #7 (**permalink**) 22-03-25, 08:06 PM

Nick - I do hope the hospital visit isn't serious and that you will be out soon.

I ordered both EMP Stewart and Stant thermostats just to be on the safe side. The car is at Transmission technology having its shift points adjusted. I will change thermostats when it gets back post an update.