How long to cool down after Short Trips...

[Menaces Nemesis]

Regarding the M923A2, I've read that some folks claim it takes forever for their truck to warm up at idle. I know the manual says to let it warm up for at least 5 minutes. And, before shutting down, to let it cool for 5 minutes if the temp is above 200F.

What's your real-world experience with the 900 series? if you warm-up, and drive to Home Depot 3 miles away, on a 70 degree day, how long do you let your M923A2 cool at idle before shutting it down? Will your truck reach 200F after only 3 miles of driving?

Tried to search this and didn't come up with anything.

Thanks in advance for your response,

MN

 

[kubotaman]

I don't know about letting the truck cool down, but it is always a good idea to let a turbocharger equipped vehicle idle for 5-10 minutes after use to prevent turbo damage.

 

[Tinstar]

Mine never gets above 200 and I always do a idle cool down after any trip.
Maybe not a full 5 minutes every time, but at least two. Depends on how hard it worked.
Was driving on Route 66 yesterday at highway speed for 45 minutes and once back at ranch did a full 5 minute cool down.

Turbo gets hot and the cool down is for the oil to cool the turbo bearings. Shutting down too soon will cook the oil around the bearings and cause problems.
Turbine Engines have same issue. A cool down from 30 seconds to two minutes depending on the engine is mandatory. Unless emergency of course.


Yes they take forever to warm up.
I start mine 30 minutes before heading out.

Remember those short trips will take a toll on the battery's if you don't drive it enough to recharge them.

 

[winfred]

letting the pre turbo egt get below 300 degrees is a good practice and generally the accepted safe shutdown temp across most diesels, i can effect the temp quite a bit on my dodge/cummins quite a bit with how i approach the parking area and use of manual tranny, down shifting/coasting in gear cools it down nicely, haven't had the pyro in my deuce long enough to have a average of how long it takes to cool but with its short gearing itll be harder to cool down with the tranny

 

[Menaces Nemesis]

Thanks for the replies... I've also read that extended idling causes "wet-packing"/carbon build-up. Is this an issue when leaving the 900 series idling for so long (30 minutes)?

 

[WillWagner]

A little heat in the engine before taking off is good, but remember, YOU aren't using these engines as they were designed to be used. In "normal" temps...65-80 degrees, start the pig, let it idle a bit 'till o/p is stable and drive out of your driveway normally, cold weather is different, I don't live there so I won't even try and give advice on that. After your "short hop" to the Deopt or where ever, the slow speed cruise thru the parking lot to the space way out in the corner will be sufficient to cool what heat you made in your no load, low rpm, no power use trip to the Depot.

On the way home, if you are buying 7 tons of concrete, the residual heat in the engine from the heart soak it did while you were purchasing the concrete will be plenty to start, let the o/p stabilize and take off. When you get home, after doing the low speed, stop and go run back, maybe let it idle 20-30 seconds and kill it, it will be fine.

Idling, low speed, low power operation is the worst thing for it. The 5 min idle before shut down thing is meant for the time when the engine would be operating at it's normal parameters, going down the road, using the power, and then a need for a quick pull over happens, THEN it is not good to shut it off. In the time it takes you to exit the hwy, stop at the lights and signs on the way home or to your destination, the turbo will cool and you can just shut the thing off.

 

[WillWagner]

Yes, idling will cause carbon packing, it still does and it is a big issue now. This condition polishes liners, meaning, it removes the cross hatch and causes oil consumption. IIRC, these could have no valve seals, depending on how early the engine is, they did no at first, so oil migration down the guides combined with no/light load, low temp operation makes the packing issue worse.

 

[Menaces Nemesis]

A little heat in the engine before taking off is good, but remember, YOU aren't using these engines as they were designed to be used. In "normal" temps...65-80 degrees, start the pig, let it idle a bit 'till o/p is stable and drive out of your driveway normally, cold weather is different, I don't live there so I won't even try and give advice on that. After your "short hop" to the Deopt or where ever, the slow speed cruise thru the parking lot to the space way out in the corner will be sufficient to cool what heat you made in your no load, low rpm, no power use trip to the Depot.

On the way home, if you are buying 7 tons of concrete, the residual heat in the engine from the heart soak it did while you were purchasing the concrete will be plenty to start, let the o/p stabilize and take off. When you get home, after doing the low speed, stop and go run back, maybe let it idle 20-30 seconds and kill it, it will be fine.

Idling, low speed, low power operation is the worst thing for it. The 5 min idle before shut down thing is meant for the time when the engine would be operating at it's normal parameters, going down the road, using the power, and then a need for a quick pull over happens, THEN it is not good to shut it off. In the time it takes you to exit the hwy, stop at the lights and signs on the way home or to your destination, the turbo will cool and you can just shut the thing off.

Greatly appreciate the insight. I'm trying to figure out if a Deuce or 5 Ton would see much use in my routine. Would it be safe to operate the M35A3 Deuce, in the same manner as you stated for the M923A2, on short trips?

 

[Tinstar]

I can't answer truck specific since I do not own a deuce.
But you will still have the battery recharge issue.

Short trips do not allow the battery's to get topped back off after a start.
Sure it starts great and all seems ok, but if you don't drive it enough or put a charger to them, it will eventually catch up to you and leave you stranded.

Our cars and trucks suffer the same way. We just tend to drive them longer.

So if it's just short little hops that you're planning it will effect your battery's, in the long run.

Another excuse for a road trip!!

 

[WillWagner]

I think the deuce will be more forgiving on the short hop and charging issue, no control box dealio, they are just a normal electrical system with no electronic features. I miss my truck, but don't at the same time.

 

[74M35A2]

The "let the turbo cool" applies more to gasoline engine that runs a much higher EGT. Diesel is cooler EGT, and even today's gasoline turbos are coolant cooled to allow quick shut off with minimal coking.

I think Will is spot on here. Your EGT is going to be cool going to Home Depot to begin with. In addition, by the time you are idling through the parking lot, she is cool.

For those that still carry the concern, you can switch to synthetic oil, as it has a much higher temp characteristics.

 

[Bill W]

I've always associated proper turbo cool down with highway driving ( ie Interstate /turnpike ) where your running along at cruise speed for quite awhile then pulll into a rest stop and simple shut down to which the overly hot turbo bearings burn off ( cook ) the residual oil in the bearing causing a dry (re) start. When I take my Ford diesel on a long trip I bring a extra set of keys so when I do pull into a rest stop I lock it up while leaving it running while I head for the bathrm or snack machine. As far as around town driving I don't give it much of a concern

 

[Csm Davis]

74M35A2 I disagree in the case of a M939A2 primarily because these engines are small for the weight of the trucks and work hard to pull the trucks up to speed for even short runs, I drive mine like I stole it and think everyone should, but I think Winfred is spot on with letting the EGTS get back down to 300 or so before shutdown. I have even thought about doing a turbo timer on my truck to help me to remember to cool it down.

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