oil, air or both?

[opjohnny]

I started a thread about the cooldown times thinking since it is cold outside maybe the one to five minute is not as critical and I could save fuel. A thought occurred to me. How much of the cooldown work is done by the engine oil and how much is done by outside air? Maybe it is not oa temp dependent and we should monitor the temp of the oil return line from the turbo bearings? Just a thought. It would explain to me why they don't say anything about shorter times when it's cold out. What does oil temp stay at for these engines? Is it all about the volume of oil run through the turbo bearings and not egt?

 

[Alan Reagan]

If the engine is shut down with the EGT (pre turbo) above 300*, it will cause the oil to coke and leave deposits on the shaft. The oil is not that hot, but would absorb the residual heat from the housing if the engine is shut down early. I don't have a gauge on this truck yet, but had one on both of my first two. Winter time, it cools fast because of the cold intake air. Summertime is when you have to worry. Winter time, just take a long cool down after a hard drive either towing or Interstate driving. The manual doesn't differentiate winter or summer because it would get too complicated for some owners to try to figure out what to do.

 

[txhawg]

The manual doesn't differentiate winter or summer because it would get too complicated for some owners to try to figure out what to do.

Yeah, in Texas you never know what season it is.

 

[nickleinonen]

in the cold temps we've been having in my area, my idle temps are down to 200°f real quick [in summer, 300°f is sometimes a long wait]

 

[jimnance]

I started a thread about the cooldown times thinking since it is cold outside maybe the one to five minute is not as critical and I could save fuel. A thought occurred to me. How much of the cooldown work is done by the engine oil and how much is done by outside air? Maybe it is not oa temp dependent and we should monitor the temp of the oil return line from the turbo bearings? Just a thought. It would explain to me why they don't say anything about shorter times when it's cold out. What does oil temp stay at for these engines? Is it all about the volume of oil run through the turbo bearings and not egt?

Cool down is mostly an old womans tale. Yes, it's a good idea, especially if you've been towing hard, but for normal city driving I never cool it more than thirty seconds before shut down. I'm on my fourth CTD. The previous two had over 100 K when sold, and the '99 almost has 100 K and I've never had any turbo problems.



This is a common sense thing. If you are tooling down the freeway pulling a trailer and running EGT's of 1200 F, sure, you need to let the housing have a chance to cool a while. Most driving isn't that way, and the housing isn't nearly as warm. Just my . 02, but I think a lot of guys worry and run the trucks needlessly long before shut down.