Diesel Cooldown

[Viejo]

I know that you should let a hot engine idle to cool down before shutting it off. I've always done it by the seat of my pants. If it seems hot, I idle it for a minute or two then shut it off. When climbing a long grade I usually stop and let it rest if transmission temp goes over 220 or oil goes over 225.

But how hot is too HOT?

Should I watch coolant, oil, trans or exhaust temp and how low should it go before I can shut down?

We're talking about a 7.3 here if that matters.