Do you leave your diesel running ...?
I see many diesel drivers who leave the engine running while fueling (or other short-term occasions). For a while, I asked why they did that, just to see what their reason was. Never got the same answ...
Forum Discussion
Old-Biscuit wrote:
By the time I pull off highway into rest area or fuel station my EGTs are already down, my turbo has cooled and there is no need to leave it running.
I can't say that an off ramp has ever been enough to cool EGTs when towing for me. The pre-turbo temps drop quick, but idle for a minute and watch them rise, or shut it down and watch them rise and fast!
Two years ago I added a time delay relay to my gauges and its amazing how much longer it takes the turbo to cool down whe using a pre-turbo pyro. I would shut it down when it reached 300° and watch it go climbing back above 400° pretty fast, which is hard on the oil in the bearing.
Now I have a post-turbo pyro in addition to my pre-turbo, and use post temps for shutdown purposes. It's not uncommon to see a 200-300° delta when idling after a tow.
I prefer post-turbo for shutdown as the turbine blades hold a LOT of heat, and that heat will rise back into the bearing as soon as exhaust flow stops.
Unless you coast for about 2-3 miles before a rest area I doubt the turbo is as cool as EGT's indicate upon stopping. YMMV, but this is something I have noticed in multiple rigs. I commonly go camping with people that shut their diesel down upon arriving, and I ask and get the coasting in comment like you made. I tell them to start it back up and watch EGT's for a minute and they always rise above proper shutdown temp.
