Diesel engine warm-up and cool down

[JDgreen227]

I drove medium duty commercial straight trucks for a living, many with diesel engines like a Cummins 5.9, so when I got my first diesel tractor it was second nature to let it idle for several minutes after starting and before stopping the engine.

Indeed, the operator manual recommends "let engine run at 950 rpm for one minute in warm weather or five minutes in cold weather after starting" and "let engine run at 950 rpm for about 2 minutes after hard or extended operation to prevent heat build up" (before shutting off).

After I start the engine, I move the tractor outside at idle speed, then let it run for a minute or two, and when done for the day, I shut off the mower, then run the engine at idle for 2-3 minutes before driving back indoors. I can understand the cool down process for a large, heavy truck engine, most of which are equipped with turbochargers, but does the cool down process for a small, non-turbocharged diesel really have that much effect on engine service life? Thanks for any input you can provide.

 

[Carl_NH]

Most manuals specify a warm up for the engine and more important the hydro fluids. On my B21 they say 1-2 min above 60* and below 45* 4-5 minutes.

On cool down aspects I think its a good idea especially if working it hard in hot weather however since its water cooled i dont really think its a big deal one way or another.

With air cooled units like my Cub or ZTR I pull up to the barn and blow off the grass and dust allowing them to idle for a few minutes to cool down. Sometimes on the Kubota I will give it a quick washdown but usually just the trip back to the barn is enough to cool off in my opinion.

 

[TripleR]

I just go by the manual.

 

[RPW]

I agree go by the manual. Shutting down a hot engine regardless of whether it's water or air cooled can be hazardous to the engine. Heat will build up after shutdown regardless of cool down period but how much heat will build up will differ. Try this, pick up an inexpensive non-contact temperature gauge (about $25 at HF). Run your tractor hard say discing or mowing for about an hour, before you shutdown get a reading off of where the cylinders are located. Shutdown and watch the temperature climb. Do it again but let the motor idle for a couple of minuets. The temperature will still climb but you will probably see that it doesn't climb as much and slower.

Good luck.

 

[RoyJackson]

I just go by the manual.

About the same...I let it idle long enough for the temperature gage to start moving, then go to work...now, if I'm going to use PTO RPM, I don't engage (the PTO) until the tractor is normal operating temperature. I normally do a walk around (looking for loose fasteners and damage) while I smoke a cigaret.

As far as shutdown...I'm on my 3rd Deere. None ran over quarter to third way up the gage during operation. I just shut down when I'm done (after reducing RPM and disengaging the PTO).

 

[JDgreen227]

About the same...I let it idle long enough for the temperature gage to start moving, then go to work...now, if I'm going to use PTO RPM, I don't engage (the PTO) until the tractor is normal operating temperature. I normally do a walk around (looking for loose fasteners and damage) while I smoke a cigaret.

As far as shutdown...I'm on my 3rd Deere. None ran over quarter to third way up the gage during operation. I just shut down when I'm done (after reducing RPM and disengaging the PTO).

By gage you mean temp indicator? I am always surprised at how cool my Deere runs, even when mowing at PTO RPM in 90 degree weather on a sunny day, my gage barely goes up to a third of the scale at the most. I usually give it a 2 to 3 minute idle speed creep to my mowing site, then engage the mower PTO, run it it 1500 rpm for a few minutes as I mow and gradually increase the rpm as the temp gage registers normal operating range.

 

[Thomas]

Like most I let the tractor warm up..colder longer,also raise fel and do bucket curls than 3 pt. hitch.
Cool down,couple mins. plus..take care of tools do tractor check.

 

[RoyJackson]

By gage you mean temp indicator? I am always surprised at how cool my Deere runs, even when mowing at PTO RPM in 90 degree weather on a sunny day, my gage barely goes up to a third of the scale at the most. I usually give it a 2 to 3 minute idle speed creep to my mowing site, then engage the mower PTO, run it it 1500 rpm for a few minutes as I mow and gradually increase the rpm as the temp gage registers normal operating range.

Yes, the temp gage...

My previous tractors were a 670 and a 790, both also ran as cool as your 4210 as does my 4400.

 

[JDgreen227]

Yes, the temp gage...

My previous tractors were a 670 and a 790, both close relations to your 770 and both also ran as cool as your 770.

I am a little HOT because you think my 4210 is a 770...nope, not really...lol

 

[RoyJackson]

I am a little HOT because you think my 4210 is a 770...nope, not really...lol

I went back and corrected it before you responded...sorry about that. I was thinking of another member who does have a 770.

 

[ModMech]

Cool down is almost completely worthless unless the engine is turbocharged and even then would only be necessary if you were *JUST* working the engine HARD.

While an engine is in use, it is almost always operating below the peak design temperature and certainly is if you lifted the deck and drove it carefully into your shop for parking. Additional "cool-down" time is not warranted under such conditions and in fact may cause more harm than you may suspect because the cylinder temperatures drop quickly when an engine is under low or light loads. This can cause fuel to burn incompletely adding soot load and unburned fuel to the oil, neither are good.

With a turbocharged engine things are a little different, it is *most* important to allow the engine to return completely to idle for a few seconds before shutting down. Failure to do so can result in excessive bearing wear of the turbo due to lack of lubrication while it is spinning down.

As an aside, I did a crude test one day out of idle curiosity. After replacing the oil cooler on a CAT 3116 in a C5500 I started the engine to check for leaks before I re-installed the air filter assembly to the turbo (it is a PITA to remove/install and in the way of EVERYTHING on the RH side). We allowed the engien to idle for a few minutes and finding no leaks I shut the engine off. From IDLE the turbo continued to spin for nearly a minute! I brought the techs over, started the engine again then shut it down. They were AMAZED that a turbo spun for that long w/o oil. The lesson is, NEVER EVER "goose" a turbocharged egine before shutting it off, unless you like replacing turbos that is.

 

[JDgreen227]

OP here, I did question about the cool down period for non-turbo diesels in my original post. When formerly employed driving medium sized straight trucks, I knew enough to let them idle down after an extended run, before killing the engine. First turbo diesel our unit had I shared with another driver, who treated the truck like a car engine, ie, almost no warmup when cold and killing the engine with no cooldown period. OEM turbo fried at 62,000 miles despite regular maintenance. (Navistar Dt-466). Replacement truck has the same engine, required CDL so I was the only driver. Was still running strong at 212,000 miles.

Thanks much for your input, you pinpointed my main query. :thumbsup:

 

[Don87]

I had a turbo go out on the International Pro Star I was driving. Cummins engine.........24,000 miles. I always do the 'warm up- cool down' routine.

EDIT: I have no clue what happened to the turbo. Techs didn't either. International replaced it under warranty.