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  1. #1
    New Member
    Join Date
    Oct 2010
    Posts
    6

    Default Need help - RPM Races During Cold Start

    Hey All,

    For the past few weeks I have been seriously looking to buy a used tractor. We really need it to maintain our land and gravel driveway. Haven't owned a tractor before, but I am learning quickly. During my search and evaluating tractors here, anytime I had a question I would google it and I would eventually end up on this site where I would find an answer. So I have signed up because I am getting closer to purchasing.

    I have found a 2006 John Deere 4120, eHydro transmission, 400x loader, with about 850 hours on it. I have checked it out and it is in pretty good shape, despite a bent power steering rod and a destroyed driveshaft plastic shield. I have been on JD website and priced parts (ouch!), but at least I know what to expect.

    However, there is one thing that I am concerned about-- the owner (who seems to be pretty honest about showing problems that he knows of) says that during the winter on a cold start the tractor's RPMs initially race to nearly the highest throttle setting even though the throttle on the column is set at low idle. He says it idles this way (at very high RPM) for at least two minutes, and then eventually it settles down to a normal idle speed. He is the second owner (traded with his cousin for it for an big RV), and he called the dealership the first time it happened. They told him it was normal in cold weather, but it didn't sound normal to him, and it doesn't sound normal to me, either. (From all that I have read, I thought that it is best to let a diesel engine warm up for a few minutes at a lowish idle.) (FYI - coldest weather here is usually in the twenties F, sometimes teens. More often it is 30s. So, not really that cold.)

    Unfortunatley, I can't test it myself and diagnose it further because it is still 70-75 degrees F during the days here, but I kinda wanna know what I am potentially dealing with before winter sets in (if I buy this thing).

    1) So, does this sound normal? Anyone heard of this before on JD or other tractors?

    2) If not normal, what could be the cause?

    3) Is this potentially a serious problem over the long run?


    Thanks for any help!

    PS - If there is already a thread on this site somewhere, just point me to it. I have searched several times, but not sure if I am missing something because I am new to the site, etc, etc.

  2. #2
    Silver Member
    Join Date
    Jun 2007
    Posts
    228
    Location
    Middle of west TN
    Tractor
    JD: LX172, X740, 3520

    Default Re: Need help - RPM Races During Cold Start

    How cold is cold? I understand it is normal for these computer controlled JD's to run faster for a short time when cranked-up cold. I have only experienced this a few times with my 3520. When cranked at aproximately 20 degrees (F), it will almost immediately (as soon as the oil pressure comes up), go to about half-throttle and run there for maybe 20 to 30 seconds before settling back to a normal idle speed. I assume that at colder temps it would run longer at the higher speed - not sure about running faster. "Near full speed" sound too high to me. Hopefully, someone else here will have a more difinitive answer.

  3. #3
    Platinum Member
    Join Date
    Apr 2010
    Posts
    975

    Default Re: Need help - RPM Races During Cold Start

    Now that you've found the price of the replacement parts, how much "discount" are you getting because of the breakage? I would set my sights on 3x the parts cost -- minimum.


    Also, 850 hours in 4 years is a lot. Was it a rental machine ? If so, I would back away slowly and when safe run for the hills.

  4. #4
    New Member
    Join Date
    Oct 2010
    Posts
    6

    Default Re: Need help - RPM Races During Cold Start

    Thanks for the feedback guys,

    Sounds like an RPM spike is not completely abnormal. I think I will try to get more specifics from the owner, and then maybe post a follow up thread. My understanding is that the spike occurs when it is in the twenties, but I want to double check his numbers, etc.

    As for discount, etc, if I make an offer I will definitely take all of this into consideration. Right now, asking price is way too high based on other machines I have seen, so don't worry, I'm not going to do anything foolish. so if I get this 4120, it has to be a really good deal to cover the other unkown problems that may exist. (I am also seriously considering a new JD 3520.)

    And I agree, 850 hours in 4 years is high. In fact, one of the first things I asked was, "So, what has this been used for?" Not a rental, apparently, but a single owner that used it to maintain his property-- grading a really long very hilly gravel drive, mowing, brush-cutting, and everything else needed on a big property. Also, he supposedly pretty much used it like a car, driving it 5 miles down the road and back regularly to vist relatives and friends. Of course, whether all of this is accurate is not really known.

    Bottom line-- I'm still considering it, but I am a little wary.

  5. #5
    Veteran Member RollTideRam's Avatar
    Join Date
    Sep 2003
    Posts
    1,260
    Location
    Hartselle, Alabama
    Tractor
    Deere 3320

    Default Re: Need help - RPM Races During Cold Start

    The tractor could have been bought in the fall of 05 making it six years old. The fast idle on cold starts is normal. Scared me the first time my 3320 did it. You will get more specific answers from 4120 owners in the Deere section. JC
    JD 3320, KK rake and tiller. Millonzi grapple, pallet forks, tooth bar. Deere Z930R
    01 Ram 4x4 2500 CTD and 22' 12k trailer, Big Tex 7x14 dump trailer.
    2015 Polaris Ranger 570 F/S eps

  6. #6
    New Member
    Join Date
    Oct 2010
    Posts
    6

    Default Re: Need help - RPM Races During Cold Start

    Thanks for the info. It's funny, but the guy who owns the tractor also said that it scared him the first time it happened as well. Shut everything off and went inside to call the dealer.

    Thanks also for the suggestion-- Yeah, I think I will post a thread in the Deere section for 4120 owners, or maybe 4x20 owners. Should have done that initially, but I was brand new to the site, and when I posted it defaulted to the general forum.

  7. #7
    Veteran Member RollTideRam's Avatar
    Join Date
    Sep 2003
    Posts
    1,260
    Location
    Hartselle, Alabama
    Tractor
    Deere 3320

    Default Re: Need help - RPM Races During Cold Start

    Good luck on your search, I would own a 4x20 if my economy would improve. JC
    JD 3320, KK rake and tiller. Millonzi grapple, pallet forks, tooth bar. Deere Z930R
    01 Ram 4x4 2500 CTD and 22' 12k trailer, Big Tex 7x14 dump trailer.
    2015 Polaris Ranger 570 F/S eps

  8. #8
    Veteran Member
    Join Date
    Feb 2008
    Posts
    1,853
    Location
    Orstraya , Ex convict stock , G'day .

    Default Re: Need help - RPM Races During Cold Start

    That's a bit over half an hour a day , don't sound too bad to me .

    If the injector pump has it's own oil reservoir and not pressure fed . The oil may need to be changed to something thinner , it may be possible the thick cold oil is holding the counterweights out .

  9. #9
    Veteran Member
    Join Date
    Feb 2008
    Posts
    1,853
    Location
    Orstraya , Ex convict stock , G'day .

    Default Re: Need help - RPM Races During Cold Start

    What did you find ?

  10. #10
    Gold Member
    Join Date
    Sep 2008
    Posts
    439

    Default Re: Need help - RPM Races During Cold Start

    since when did 850 hours in 4 years become alot? 212 hours/year doesnt seem like very many. rental equipment could easily show 800+hrs/yr; if used 8 hours per day, 100 days per year. that still isnt *that much*
    heavy equipment/heavy truck mechanic/heavy haul trucker
    2007 Kubota L4400
    1997 Ford F-Super Duty flatbed, now 24v cummins powered
    2-71 Detroit Diesel powered generator
    '52 farmall super m
    Massey Ferguson 50a backhoe
    an odd collection of wheel horses
    Nothing runs like a yanmar, right?

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