Diesel Warm-Up -- How Long -- Why?

speedbump · Oct 17, 2011

I never knew for sure what the reasoning was, but was always told not to start/stop them a lot and to let them warm up. My 4520 when it first starts doesn't sound like a Diesel, it sounds like a gas motor. In about 3 to 5 seconds, it starts sounding like it should. I have always wondered what they did to make them do this. I think it has something to do with cold starting, cause in the last two winters here, we had some 30 degree weather and the 4 year old John Deere started just like it does in August. It's running before I can turn the key back to the run position.

If anyone knows why it sounds like it does the first few seconds, I sure would love to know why.

sweep · Oct 17, 2011

Short Game said:
A habit I developed has been to get into a "granny" gear and idle out of the tractor port. I guess it just makes me feel like I'm getting somewhere as the engine warms up. I would never have guessed that the idle, where it's set from the factory, could be detrimental. I spend hours at idle when I'm running my splitter. I don't need a 41 HP splitter. Now I wonder how many hours I'm taking off my engine's life. Is idling at 800 to 1000 RsPM that terrible with essentially no load?

And thanks to everyone for the interest in this question.

I keep my tractor under the house in a garage and start it up and idle it out of the garge so the house does not get fumed up. I always figured it was best to warm up the tractor at low idle. Guess I was wrong too.

I just looked at my owners manual and it said to set the throttle at 1/4 to 1/3 throttle during warmup so that is what I am going to start to do from now one once it gets out of the house.

Short Game · Oct 17, 2011

sweep said:
I keep my tractor under the house in a garage and start it up and idle it out of the garge so the house does not get fumed up. I always figured it was best to warm up the tractor at low idle. Guess I was wrong too.

I just looked at my owners manual and it said to set the throttle at 1/4 to 1/3 throttle during warmup so that is what I am going to start to do from now one once it gets out of the house.

Oh, RTFM! The manual only mentions a warm-up for starting in cold weather: "5~10 minutes at 1500 rpm." It calls for 1~2 minutes cool-down after "heavy work."

It also says to only start it from the seat and never indoors. That could get tricky unless your sheltered parking is on a slope that lets you roll it out, or you have one of those rigs that tow airplanes around the airport. We know how a lawyer would do it now.

whiskywizard · Oct 17, 2011

Here's my routine:

Always use pre-heat or glowplugs when starting a cold engine. If already warm , skip pre-heat/glowplugs. Many are automatic anyways. If you need to better define "Warm", consider it an engine that is warm to the touch, ~100F and higher, on rad hoses or cylinder heads, or block.
Immediately upon start up, allow it to idle at dead low idle speed and confirm it develops oil pressure and smooths out. This is a matter of seconds not minutes. If you don't see oil pressure within about 5 seconds, shut down and regroup. On a cold engine with full instrumentation, oil pressure at idle can be as low as 15-30psi, or on more simple applications, watch for the oil pressure warning light to extinguish.
Continue to idle at low speed for about a minute more, monitoring oil pressure.
Bump up to a fast idle - just come up 300 to 400 RPM above idle. This applies a small bit of load and some more fuel to aid in warm up. Continue this warm-up until coolant and oil begin to warm up. One way to tell is to watch for the coolant to just begin to show temperature on the guage. In warm weather, this might be 3-5 min. In cold weather you'll need to add up to 5 minutes more. If it's really cold, you may need to apply some more light load or the engine won't warm up. As suggested by some guys earlier here, travelling to the work site as the engine warms fully is a very good approach.

For HSTs, don't forget that the hydrostatic oil must warm up too or you can damage the pump(s). And that volume of oil is very large and doesn't get the direct heat that engine oil gets. You may well have to warm up your hydrostatic drive for longer than the tractor's engine before you apply any appreciable load.

When you look at the world's longest-lived diesels, the ones that go 10,000h and more, they show up in things like workboats, ferries, heavy equipment, large generators, etc. One of the things they have in common is they operate at a continuous and low speed always under load. Many are run with >50% load 24/7, and some even have their oil changed on the fly without ever shutting down until it's time for an overhaul. Hard to do on a compact tractor! So the best way we can approach those ideal operating conditions is to avoid the negatives:

Never load it up while still cold,
Never run it for extended periods without load, and
Never overload it (over-propping on a boat, lugging in too high a gear, etc)

brin · Oct 17, 2011

When I take my Tractor out of my garage to drive 5 miles to the farm...I start it up raise the FEL, raise the Bush Hog on the 3 Pt and back out...I run the tractor to the county road...about 2 minutes and then take off to the farm in...high gear and on high speed..I go 5 miles at 13 MPH maxing out the RPMs...Is that wrong..? I use my NH - TC 29D for this most often and have never had a problem....I looked in my owners manual and it does not say anything about warming it up before driving or operating.

dodge man · Oct 17, 2011

There is some old school thinking that I don't think is valid on smaller diesels. It used to be diesels always ran a 15w-40 oil, and large diesels have a lot of it, gallons in many cases. It takes some time to warm up all that oil and get it flowing. On many compact tractors, they are running smaller amounts of oil and thinner oil. My Kubota calls out for a 10w-30, and I run a synthetic, so it doesn't need warmed up as much to get it flowing. Just like gas engines, modern diesels have much better tolerances and designs than they did 30 years ago.

Just my opinion here, but a modern diesel in a compact tractor should only need warmed up a couple of minutes on a warmer day, on a cold day, maybe 5 minutes or a little longer. And I also try to work the hydraulics easy when its really cold and let them warm up also.

whistlepig · Oct 17, 2011

My owners manual says to warm up the Hydro a few minutes before working the tractor also.

Travelover · Oct 17, 2011

One observation - how many posts do you see here of people that have prematurely worn out their tractors? Or even worn out their tractor, period?

We spend more time worrying about where to mount a tool box or how to ballast our tractors. :laughing:

DAY · Oct 17, 2011

Size matters! My 850 has 4.7 qts of oil, and 27.5 qts of hyd. fluid. In comparison, the Yella Fella has twice the amount of engine oil, and 14 GALLONS of hydro. At zero F on a January morn, that will take some time to warm up. . .

Soundguy · Oct 17, 2011

i like to start my diesels, then walk around and kick tires and inspec and whatnot, and give them a bit to warm.. mostly the hyds IMHO..

on shutdown, i do similar to protect turbo.. walk around.. hit a few grease points, sweep a mower deck, then kill her..

soundguy