I know shutting down at too high of a temp is bad for the turbo but what is considered too high? I always try to get down to < 350 EGT before turning off the key. I have always run Rotella T6. In winter the EGT’s drop quickly but in summer I have to turn off the AC to get down to 350 in a somewhat reasonable time. But 350 is pretty much an arbitrary number that I just picked.

 

Pretty much what I shoot for or until the temp appears to "equalize" and stop dropping as fast.

There are times it will take 3-5 minutes if you just got off the freeway and are towing for example....use your best judgment is what I do.

 

Curious why this matters. I get making sure the turbo is not spooled before shutting the oil off to it, but I’m not understanding waiting 5 minutes for the EGT to drop to cold. I mean it drops like a rock for me at idle anyway since I really have very little back pressure. Inquiring minds…….want to make sure I’m not missing something.

 

High Heat soak.

Can cook the oil and possibly seals

 

So I typed the question into google and then cut-and-pasted the AI answer in below:

You cool down exhaust gas temp before shutdown, especially in turbocharged engines,

• Turbocharger Protection: Turbos spin incredibly fast and get extremely hot; shutting off the engine stops oil flow, but the turbo stays hot. The remaining oil in the bearings bakes, forming carbon deposits that can block oil passages and destroy the turbo.
• Prevent Oil Coking: The heat "cooks" the oil in the turbo's cartridge and feed pipes, turning it into abrasive sludge that ruins the bearings.
• Reduce Thermal Stress: Rapid cooling causes metal parts to contract unevenly, leading to cracks or warping in the exhaust manifold and turbo components.
• Protect Seals & Gaskets: High heat degrades nearby hoses, seals, and gaskets over time, causing leaks and failures.

How to Do It

• Idle for 1-2 Minutes: After hard driving or high loads, let the engine idle to allow oil and coolant to continue circulating and cool the turbo gradually.
• Drive Gently: Normal driving from a freeway off-ramp to home often provides sufficient cool-down.

When It's Most Important

• Immediately after heavy loads, towing, or aggressive driving.
• While modern synthetic oils help, the risk of coking is still present with hot shutdowns.

 

Why?

I have more questions, but that is the main one.

 

When I had my 7.3 L, I did worry about this. But with a 6.0 L, per the original talking points from International and, I believe, Garrett, this turbocharger is supposed to be designed for a quick oil drop when it is shut down, thereby eliminating the need for a cooldown. I’ve never had a coking issue.

The Google answer is generic across all turbocharger designs. International in-service also provided an improved drain tube to remove oil more quickly during shutdown. In the 22 years I've owned a 6.0 and been on multiple forums, I’ve never heard of a coking issue with a 6.0L turbocharger. At least per the memory of a 72 yo guy.

 

Another thing to keep in mind is if you're a KC ball bearing turbo as opposed to the bushing type most of us have. I watched a video from Charlie and he mentioned the ball bearing turbos are not as forgiving as the bushing type, and proper cool down is absolutely crucial to bearing life.

 

That’s why I was asking. After rebuilding my turbo I just couldn’t possibly see where any damage could occur especially since it’s designed to function intermittently upwards of 1200 and 1300 degrees. Granted, nobody is gonna turn the key to off when EGTs are 1000 degrees, if that’s even possible. But if you do wait until the EGTs are 350 or whatever, where is your probe? At the manifold? So what’s the temp of the turbo? 350? 400? 200?

 

I use 400*f as my target, probe in driver's manifold. That seems to be where the truck runs at if I let it idle a long time, so not completely arbitrary, more of it's normal baseline temp.

For me is a combination of all of the above plus more. Why not use cooler exhaust flow to cool down the turbo? Plus it's not just the turbo, also the manifolds and all the band clamp joints. Oil through the turbo, oil through the engine bearings. Coolant cycling through the front cover and heads. Valve train, oil rails, hpop, EGR and oil coolers. Transmission fluid if it's an automatic. These things aren't young anymore, seals aren't as flexible as they used to be.

When DD'ing I don't ever have to let it cool down, but when it's working I give it all the time it needs. I was pulling a shipping container with the dually last week, ECT was pegged to 223* and the fan was running full time, EOT was 230*, EGTs over 1000* for an hour straight towing, it was almost 90* outside. I let the thing idle for half an hour and got ECT/EOT down to 190/200 before shutting it off, EGT only took a few minutes. No sense to me in beating a horse I paid for.

Same reason I let it warm up before I drive away if it's hooked to a trailer. I remember Anthony saying he would let his truck warm up to full temp before driving it at all, and he put more miles on a 6.0 than four average guys combined.

 

I always warm up a vehicle.

 

Agree….. warming up is a must as it gets the oil up to temp which important for various reasons in these engines. The high idle is there for a reason!