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Deere 4024 Oil Pressure Drop Off - Atlas XAS185

Discussion in 'Shop Talk' started by MarshallPowerGen, Jul 8, 2019.

  1. MarshallPowerGen

    MarshallPowerGen Well-Known Member

    Joined:
    Nov 27, 2017
    Messages:
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    Occupation:
    Diesel & Generator Mechanic
    Location:
    Coeur d'Alene, Idaho
    Have an oddball issue on an Atlas Copco air compressor with the always fun Deere Powertech 2.4L 4024.
    Came in for shutting down on low oil pressure, hooked mechanical gauge up and confirmed it starts up, runs up to temp and holds 55psi, then drops to zero. Pressure comes right back up at restart, then drops after a minute. Service manager recommended replacing the engine, but I got stuck with tearing into it and was told to pull the engine and check the pump and pickup.

    No glitter in the pan or oil, pickup tube O-rings were good, no RTV or dirty bits in the pickup, opened up the oil pump (built into everyone's favorite front cover) and found a small groove going through. Opted for a new front cover (w new oil pump and relief valve) and new pickup o-rings, checked and cleaned everything, serviced the engine. Started up, ran for 10 minutes and then exact problem. Holds 55psi, then suddenly drops off. Start right up again, will hold 55psi, then drops after a minute or two.

    Looking where to even begin to start? Any oddball stuff in the oiling system in these?
     
  2. mg2361

    mg2361 Senior Member

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    Which side of the engine are you reading oil pressure? One side (the left side, engine oil filter side) would be oil pressure for your bearings, etc, the other side (right side) would be your advance oil pressure. The advance oil pressure would be normal oil pressure cold and drops to zero as it warms up. Where is the sender mounted? On the correct side? Should be near the oil filter/filter adapter.
     
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  3. MarshallPowerGen

    MarshallPowerGen Well-Known Member

    Joined:
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    Occupation:
    Diesel & Generator Mechanic
    Location:
    Coeur d'Alene, Idaho
    Well, now that is interesting. The factory LOP sensor is mounted on the non filter side middle port, that it where I've been reading the pressure from. I'll have to put my gauge in on the filter side and see what it reads.

    Any explanation what the point of the "advance side" that drops down is for? Curious for myself, and also how I'd explain to management and the customer, and why it was working okay with the LOP sensor until this point.
     
  4. mg2361

    mg2361 Senior Member

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    First let me back up. Is your engine mechanical injection or electronic injection? If it is mechanical injection then the scenario I mentioned above applies. If it is electronic then it does not apply. Easiest way to tell is if has the Aneroid on the right rear of the block or an electrical connector at the same spot.

    As far as the advance operation, it is controlled by oil pressure in the hydraulic roller cam followers, or lifters, for the unit pumps. During cold starting, engine oil is sent by the cold advance thermostat (mounted inside the right rear of the block under a plug) to the cold advance piston in the cam follower. The oil pressure lifts the piston 1.5 mm, increasing the overall travel length, or stroke, of the unit pump plunger. This advances the pump timing. The cold start advance thermostat begins to block the oil flow when oil temperatures reach approximately 80°C (176°F). At approximately 15 psi oil pressure, the cold start advance is fully disabled. From my experience the cold start thermostat will shut oil pressure off completely.
     
    Last edited: Jul 10, 2019
  5. MarshallPowerGen

    MarshallPowerGen Well-Known Member

    Joined:
    Nov 27, 2017
    Messages:
    204
    Occupation:
    Diesel & Generator Mechanic
    Location:
    Coeur d'Alene, Idaho
    Thanks so much for all the info. Got into work today, and it is mechanical injection. Installed my other oil pressure gauge and ran it up, the advance side dropped down with the filter side held steady. Went out and checked the couple of machines in the yard, and both had the LOP switches mounted next to the lower radiator hose inlet. Put a mechanical gauge on the advance side of one of those and ran it up to temp with the same results. I rerouted the LOP switch to the correct side and ran it for a while today.

    We don't know the history of the machine (customer bought at auction), and the connectors to the LOP switch were definitely not factory. The port where the other machines have their switch was either never drilled in this one, or was filled in (looked like a mess either way), so my guess is someone just stuck a switch in the first port they could find and decided the machine was bad.

    Thank you so much for your help and all the info, there wasn't even any reference to the oil pressure drop off in the FSM I was able to dig up in my generator files, so you definitely saved the day.
     
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