I've got 4014 motors. No issues to speak of.
Yes, considering the number of those engines that are out on the market the majority have been running without issues.
You are one of the lucky ones. We have a customer with 100 Sullivan Paletek air compressors with that engine and we have seen aproximately 50 of them with issues. He had since started unloading them and is buying compressors with a different engine.
What are the main things that make the 4024 less desirable?
Mechanical engines:
When those engines first came out we thought it was about time Deere built a smaller diesel. Within months of the introduction we were seeing multitudes of injection pump failures. I myself have been into over 100 of them either replacing injection pump springs or the pumps themselves. Some of those spring failures caused the injection pump lifter to lift far enough out of the bore to disengage from the key in the block and spin which then ended up ruining the block. Then we started seeing injector issues with the little washer under the injector crushing and then losing it's sealing ability allowing compression into the crankcase (hard starting/blowby issues). Then we moved on to timing gear cover leaks and water pump leaks. Those items are fixable and can be made to be reliable. Since I have done so many of those repairs I came up with a solution that works better than the Deere solution. Then move on to aging engines. we saw a fair share of (again fixable) fuel return line check valve failures which makes for difficult starting. From that some customers starting using ether. Then we started seeing cam gears that spin on the cam (they are not keyed) and consequently causing the valves to contact the pistons bending the pushrods. Then we were getting a rash of injection pump cold start issues with the cold start thermostat (uses oil pressure to change injection timing). On top of all this there were many running issues due to the pumps not being synchronized correctly causing exhaust flutter, irregular running, cold start misfire, hard starting and what we call a machine gun hunt (which is a very rapidly changing engine rpm) which only happened in the 5030's. We also saw many rack issues with the injection system as well as the rack magnet displacing causing limited rack movement causing hard starting and if you could get it started it would only rev to about 1/2 throttle. Shall I go on?
Electronic engines:
We thought, finally getting rid of the mechanical injection pump issues, yay! NOT! The issues we have seen with the electronic engines, while fewer, were still a black eye on Deere. Cam gear spin is still an issue. We have one in the shop right now with that issue. Hard starting is the biggest issue with the electronic engine. Causes have been spread out. Fuel return check valves are still an issue. Slow cranking causing erroneous cam sensor readings making hard starting. Customers using 15W-40 oil which can make hard starting (I only recommend 0W-40 synthetic). Injector failures. And the biggie is injection pump failures again. We have had quite a few with this issue and are starting to see more as they age. I just had one 2 weeks ago with hard starting and that one was the injection pumps. They wear prematurely, enough so that air can get into the fuel system through the pump plungers causing what simulates bleed back of the fuel.
There is a reason Deere stopped manufacturing this engine. And as far as replacement, you can no longer buy a complete engine, just long blocks. All the rest of the parts are still available however.....for now.
So from my end working at a dealer and seeing an endless supply of work from these engines I am a little skewed in my opinion of them.