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D8R how much smoke ? 3406c engine

Discussion in 'Dozers' started by mobile-tech, Oct 23, 2019.

  1. mobile-tech

    mobile-tech Member

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    we have a D8r was rented out got a call for a strange noise and excessive smoke , found exhaust adapter leaking and machine was indeed smoking a lot while trying to push , seemed to have plenty of power , was close to home so lowboy"d it back to the shop , after running with outer filter and inner filter replaced stile smoky, also noticed it was starting to ,melt the dust ejectors guts and when put under load blow soot out air cleaner , so I replaced exhaust adapter between turbo and other adapter that goes to muffler , muffler and stack new few months back - cat part, I pulled the intake boots off and pulled pipe plug on after cooler and blew it out - didn't notice any carbon in charge piping , I replaced all injection nozzles with cat remans , I pulled fuel ratio valve and replaced diaphragm , springs, o rings and rods , changed the little oil screen in there as well , install new air filters , run machine stile smokes not as bad , stile have black smoke pushing out air cleaner with I load her up , pulled boot from pre-cleaner to air cleaner assembly , dust ejector is melting turned my outer filter sooty in 10 min of run , so I blew filter out and reinstalled and left boot off to pre-cleaner so just sucking air right to filters , noticeable less smoke I can push material til mechine stops or spins tracks and have just a slight haze of smoke , is this acceptable ? we barely run this machine most of the time its rented out , the customer started that he fired it up after siting and it was noisy and smoky , I noticed they also replaced the tubbing from the exhaust to the pre-cleaner dust ejector , so I obviously I have to replace the dust ejector must be allowing hot exhaust gases back into it self
     
  2. John C.

    John C. Senior Member

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    It kind of sounds like the muffler could be partially plugged up. I've seen on other machines where a baffle in the muffler would break and fall over the inlet pipe. We found the problem by pulling the muffler and shaking it around real hard and heard the rattle.
     
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  3. tctractors

    tctractors Senior Member

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    Try looking at the valve adjustment as you might have a knackered camshaft?
     
  4. Mark250

    Mark250 Senior Member

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    Check to see if you have the right stack. in the bottom there should be a venturi that makes the dust ejection system work. I have seen where the stack has been damaged and it has been shortened and the venturi system has been cut out or the pipe has been made to fit upside down
    Mark
     
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  5. Nige

    Nige Senior Member

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    Agree with Mark. Also consider the possibility that the venturi in the exhaust stack has corroded so much that it has fallen apart. That will also cause hot exhaust gas to blow back through the dust ejection system into the air filter and melt everything. Flip the rain cap on the top of the exhaust stack and shine a flashlight down the stack, see what the venturi looks like.
     
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  6. mobile-tech

    mobile-tech Member

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    the stack and muffler are a couple months old , cat oem parts , I got the new dirt ejector in Friday , I pulled stack and verified stack and venturi is clear have tubed pulled off and shine flashlight threw it was clear , left tube to dirt ejector off , Iam getting exhaust out of where tube connects to muffler/stack ,pretty straight forward system , the stack pipe has indentations 3 off them toward the bottom , Im pretty sure the old stack was the same , she was pretty rotten when I replaced it
     
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  7. Nige

    Nige Senior Member

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    As the Chinaman would say - Sum Ting Wong

    The vaccum is created in the dust ejector system by the open end of the venturi pipe being just below the three dimples in the tube. The physics behind it is that the exhaust gas is compressed as it passes through the dimples. When it is allowed to expand again it creates a drop in pressure. That drop in pressure is right where the opening of the suction tube for the dust ejector is located and creates the suction in the tube.

    The illustration below (from a different machine, but the physics remains the same) shows it, not very clear but it's the best I oculd find at short notice. You can see the end of the suction tube (circled) down below the dimples.

    upload_2019-10-28_17-52-18.png
     
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  8. mobile-tech

    mobile-tech Member

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    that's what I got the dimples or indentions right below that is my venturi tube of suction tube , ill double check to make sure that tube is centered between those dimples , when I ordered the new exhaust my dealer called me and back and said the part number had been updated , but everything looked the same when I received it
     
  9. mobile-tech

    mobile-tech Member

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    D87E7D50-B5CF-4992-A507-050E17302474.jpeg ADE2D2DC-0055-42EE-9299-F6ED3BDA3A25.jpeg 63DD7285-704D-48A0-B1A7-C904E7249DB0.jpeg
    Looks pretty darn center to me .
     
  10. Nige

    Nige Senior Member

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    The centre one of your three photos. Do the dimples really come as close together as they appear in the photo..? They look like they are almost touching.
    The distance between the dimples should be about the same diameter as the O/D of the suction tube.

    Another question. In your 3rd photo the flange for the suction tube appears to be part of the muffler outlet tube. Are the dimples in the exhaust ejector tube that clamps on to the muffler.? If so try loosening the clamp and moving the exhaust ejector up or down a bit on the muffler to see whether there is a sweet spot somewhere that gives you the correct suction.
     
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  11. mobile-tech

    mobile-tech Member

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    Yes they are that close , not much clearance between them , but there is some , I thought it was awful tight when I was installing the stack , I’ll try and move stack up I’ve got it pushed down is far as it will go , just seems like the center of that stack should be opened more , original parts usually seem to be right on the money
     
  12. Nige

    Nige Senior Member

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    My rule of thumb is that the gap between the inside of the dimples should be approximately equal to the outside diameter of the suction tube, give or take.

    I cannot believe that the dimples are supposed to be as close together as that, but then again I've never had the genuine parts for a D8R in my hand before so I cannot say with any certainty one way or the other. It just doesn't look right.
     
    Last edited: Oct 28, 2019
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  13. mobile-tech

    mobile-tech Member

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    Well I tried moving it up and down, stile the same result, blowing exhaust blowing out ejector section hole , looks like tomorrow I’ll modify those dimples a little , it’s a simple system , shouldn’t be this much messing around , haha yeah right , just turned into one of those jobs
     
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  14. RZucker

    RZucker Senior Member

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    Somewhere in the ejector plumbing there should be a check valve with a stainless flapper that prevents back flow from the stack when the rpm drops and comes back up, such as reversing the tractor. But I think you have a stack problem too.
     
  15. mobile-tech

    mobile-tech Member

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    Yeah dust ejector is new , replaced it the old melted apart , there’s a stainless flapper valve in there , but I think your right as well , believe the dimples are too tight In the stack to establish good Venturi effect
     
  16. mobile-tech

    mobile-tech Member

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    This a picture from bottom of stack , or as it’s called dust ejector on sis , those dimples are 18 1/2 long in that pipe , don’t know if I’ll be able to modify them , don’t wanna trash a $330 pipe from cat
     

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  17. Nige

    Nige Senior Member

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    I understand what you're saying and here's what I suggest. Take that photo above to the Cat dealer where you bought the ejector, make sure you have the Part Number (7C-2991.?) of the ejector to hand. Ask the Parts guys to have their Technical Communicator contact Cat via the DSN system to have the dimensions of the ejector checked against the measurements given on the engineering print for the same Part Number. That would settle the question once and for all whether the dimples are correct or not, but in my opinion they are far too close together and are effectively plugging up the flow of exhaust gas up the chimney.

    As a work-around for now you could install a blanking plate over the 2-bolt flange where the hose from the air cleaner connects to the exhaust ejector. All that will do is result in the air cleaners needing servicing at slightly shorter intervals than normal because the larger dust particles will not be getting sucked up the exhaust stack like they normally would.
     
  18. nicky 68a

    nicky 68a Senior Member

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    My experience in D8R's is fairly simple.......If they start smoking,farting or fluttering even a little bit,it's doom for the cam.
    I think it would be prudent to measure up the valve clearance whilst you are under the bonnet before it blows the engine to bits.
    I've had this twice.Each time I thought it was muffler,or fuel injection issues and each time I was wrong.
    Thankfully,I had the good sense to take advice from my fitter chap,so no massive harm done.
    I think your D8 engine will be seeing daylight soon.
    Sorry.
     
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  19. Nige

    Nige Senior Member

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    Excellent first-hand experience Nicky. Worth its weight in gold.
    It might also be worth the OP posting the tractor Serial Number, just so everyone knows which iteration of the D8R we're actually dealing with.

    Nicky, a question for you. What change interval do/did you use on the engine oil & filter on your 8R's. I'm not sure if you still have any.
     
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  20. mobile-tech

    mobile-tech Member

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    I’m curious to that as well , also what kinda of hours we’re you seeing cam failures at? We are running 250 hours on the oil , filter , and outer airs
     
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