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  1. #11
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    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    I can't tell from the pic it's too blurry,a couple things can cause no oil pressure, bad pump, suction screen stopped up or a bad cam bearing that has turned blocking the hole,I would think that if there is no rod knock,the bearing you are seeing is a cam bearing

    Tommy
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  2. #12
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    John Deere 3720; AgPro 354

    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    Bad cam bearing... Ugh. Ok, thanks, Tommy. I'll do some searching and see if I can find a thread on pulling the cam shaft. I'll also inspect the oil path up to the filter port some more to see if I can find bits of the bearing clogging it up.
    John Deere 3720 w/ FEL, backhoe & 72" mid-mount mower
    (retired) AgPro/Jinma 354 w/ Koyker 160 FEL
    6' bush hog, 6' King Cutter tiller, 6.5' King Cutter disk harrow

  3. #13
    Elite Member Bob Rooks's Avatar
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    Yuchai Bulldozer

    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    Tommy is correct about the spun cam bearing, but I don't think thats the issue here because cam bearings are of the plain type and dmgks said "bearing race" which suggests a roller or ball bearing. The only ball bearings I'm aware of are located in the accessory drive for the hydraulic pump/s on the right front of the engine. The only other place is inside the fuel injection pump, but I think we can rule that out.
    Just for a quick check, I'd pop that hydraulic pump off to see if you will have to remove the timing gear cover.
    Yuchai 306R dozer, Mustang 2040 skid steer, Mitsubishi MS035 Mini-Ex with four buckets and a rake, 7' Dual Dozer with dual Trimble machine control GCR-2SM laser receivers.

  4. #14
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    John Deere 3720; AgPro 354

    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    Good point, Bob. I do believe it's a race because it's tapered. I'll pull the hydro pump and report back.
    John Deere 3720 w/ FEL, backhoe & 72" mid-mount mower
    (retired) AgPro/Jinma 354 w/ Koyker 160 FEL
    6' bush hog, 6' King Cutter tiller, 6.5' King Cutter disk harrow

  5. #15
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    John Deere 3720; AgPro 354

    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    Well, good news and bad news.

    The good news is I found the ultimate cause of the problem. Suffice it to say that when the experts are stumped it can't be a good thing.

    It isn't.

    Just to get your mental juices flowing again, remember that the tractor started missing at the same time that the oil light came on and it stopped producing oil pressure.

    Today I pulled the hydro pump. The (ball) bearing looked fine. No evidence of metal shavings in the timing gear cover under the hydro pump drive gear. Hmph. Next I checked the oil passage between the oil pump and the oil filter. Clean as a whistle. I immersed the oil pump in some oil and turned it by hand. It pumped oil like it was supposed to. Next I pulled the timing gear cover. Gears all look pristine, no shavings in the cover at all. Next I tried to figure out if I could pull the camshaft without pulling the head (I'm an amateur). Nope. So I pulled the exhaust manifold then the valve cover. Didn't see anything telling in there, although I did see that the washer thingy on top of one of the valve springs had fractured and was sitting on the top of the head:

    That didn't look like it would be the cause of my problem, though. I did notice something odd: A couple of the push rods had a gap of between 1/4" and 1/2" from the top of the rod and the rocker arm. That seemed excessive.

    So I hopped on my creeper and looked up from the bottom again, turned the crankshaft and... Voila!

    I kept coming back to the basic question: "What would make the oil stop flowing at the same time the tractor starts missing?"

    Well, the oil pump works and the oil passages are clean, so the only explanation seems to be that the oil pump isn't getting turned. But the oil pump is driven by the cam and the engine was running, albeit missing. I thought in one cylinder, but discovered today that it was missing in two.

    Figured it out yet?

    Hint: Turns out it's the rear two cylinders that are missing.

    Hint: They're missing because their valves aren't moving.

    Cause: I've never heard of this before, but the cam shaft appears to be broken right in the center, where it appears to be supported by a (now destroyed) bearing. Turning the engine confirms this: The front of the cam rotates, the back half of the cam remains stationary.

    I haven't pulled the head yet but I'm afraid of what I'll find when I do. Will I find broken valves in the two rear cylinders? Damaged heads? This is looking like it's going to keep getting uglier...
    John Deere 3720 w/ FEL, backhoe & 72" mid-mount mower
    (retired) AgPro/Jinma 354 w/ Koyker 160 FEL
    6' bush hog, 6' King Cutter tiller, 6.5' King Cutter disk harrow

  6. #16
    Elite Member Bob Rooks's Avatar
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    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    Quote Originally Posted by dmgks View Post
    Well, good news and bad news.
    ..... although I did see that the washer thingy on top of one of the valve springs had fractured and was sitting on the top of the head.
    That's a valve spring retainer - you may also be missing a keeper. This type of failure is very uncommon.

    I've never heard of this before, but the cam shaft appears to be broken right in the center, where it appears to be supported by a (now destroyed) bearing. Turning the engine confirms this: The front of the cam rotates, the back half of the cam remains stationary.
    This is not uncommon for engines with high hours and a couple of rebuilds under their belts.

    I haven't pulled the head yet but I'm afraid of what I'll find when I do. Will I find broken valves in the two rear cylinders? Damaged heads?
    Doubt the head is damaged unless a valve rolled over or a valve seat fell out (which could be the smoking gun for this).

    This is looking like it's going to keep getting uglier...
    Well, once you get it apart you will have to qualify all of the used parts to see what can be reused. Just remember, it could have been worse.



    12345
    Yuchai 306R dozer, Mustang 2040 skid steer, Mitsubishi MS035 Mini-Ex with four buckets and a rake, 7' Dual Dozer with dual Trimble machine control GCR-2SM laser receivers.

  7. #17
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    John Deere 3720; AgPro 354

    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    Update: I decided not to pull the head myself because I was getting a little uncomfortable with my abilities at this point. I have never done this before. I found a machinist/engine shop in a nearby town and brought the engine (sans all the parts I'd already removed) to him. Although he doesn't have experience with Yangdongs, he works on agricultural diesels and doesn't seem intimidated. He'll tear it apart and get with me once he figures out what needs to be done.

    More as it develops...
    John Deere 3720 w/ FEL, backhoe & 72" mid-mount mower
    (retired) AgPro/Jinma 354 w/ Koyker 160 FEL
    6' bush hog, 6' King Cutter tiller, 6.5' King Cutter disk harrow

  8. #18
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    John Deere 3720; AgPro 354

    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    Update: Well, nothing to report, really. The engine is still at the diesel mechanic's shop. But I appreciate the advice I got and will post an update once I hear back from the shop.
    John Deere 3720 w/ FEL, backhoe & 72" mid-mount mower
    (retired) AgPro/Jinma 354 w/ Koyker 160 FEL
    6' bush hog, 6' King Cutter tiller, 6.5' King Cutter disk harrow

  9. #19
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    John Deere 3720; AgPro 354

    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    Ok, I'm back to banging on this thing...

    The reason it's taken me so long is that, when I discovered the broken cam, I took the engine to a shop to have the cam replaced. The guy sat on it for a year (I have my JD, so I wasn't in a hurry). I finally went and rescued the engine from him and resumed working on it myself.

    I got the cam out (both pieces) and punched out the forward bearing. That's the only bearing I could see that was damaged, and does appear to match the pieces in the oil pan. I'm thinking I should replace the mid and rear cam bearing while I'm at it.

    Questions:
    1) Should I replace all three cam bearings?
    2) If #1 is yes, then it looks like I would need to pull the crank to get to the mid cam bearing. If I pull the crank, do I need to replace anything, or can I reuse the crank seals and bearings?
    John Deere 3720 w/ FEL, backhoe & 72" mid-mount mower
    (retired) AgPro/Jinma 354 w/ Koyker 160 FEL
    6' bush hog, 6' King Cutter tiller, 6.5' King Cutter disk harrow

  10. #20
    Platinum Member
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    Jinma JM304

    Default Re: Y485T lost oil pressure - how do I drop the oil sump?

    I think it is a false economy to reuse any bearings or seals when rebuilding an engine. So you spend another hundred bucks on all new stuff - what is your time worth to tear it down again? I rest my case.
    Last edited by Rich Waugh; 11-02-2012 at 11:31 AM.

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