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Using machine with worn rings?

Discussion in 'Skid Steers' started by motochris, Sep 8, 2012.

  1. motochris

    motochris Active Member

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    I just picked up a Bobcat S175 from a buddy. It smokes a decent amount when cold, though it goes mostly away when warmed up. It's hardly noticable at idle and just a bit of smoke under load.
    He had just had the injectors and pump replaced thinking that was why, but it continued to do it. The local dealer checked it out and said it needed rings. At this point he doesn't want to mess with it so he sold it for a good price to me.
    What I'm wondering... how much will it hurt to continue using it like it is for a while? Its runs great, hasn't used any oil I've seen, though I've only put about 15 hours on it.
    I bought this machine is for home based use. If it gets used much over 50-60 hours per year by me, I'de be highly suprised. 100 hours a year tops for sure.
     
  2. Scrub Puller

    Scrub Puller Senior Member

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    Yair . . . motochris. Mate if it needs rings it's already hurted . . . but if you haven't topped up oil in 15 hours it can't be too hurted. At a 100 hours a year it probably will be good to go for a while yet.

    Lack of compression for starting could eventually get you . . . and a gasoline soaked rag on the intake will probably get you a couple of years more.

    Cheers.
     
  3. motochris

    motochris Active Member

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    Starts right up, no issues at all really. If I didn't SEE the smoke when its cold... I wouldn't think it has an issue at all.
    Basically... I've already talked to my local machine shop and they'll rebuild it for me for $1500 if I bring them the long block. Plenty good price, but I have about 40 hours worth of work that needs to be done before the end of the year. Light duty stuff... mainly using a bucket I setup to screen rocks from dirt, to get the rocks out of an area for our horses.


    rockbucket.jpg

    I'll get pics of it running cold and warm so you guys can see it. Maybe its better/worse than I'm thinking.
    It really doesn't have much time on it.. less than 1300 hours, but it was a theft recovery from a rental yard so we really don't know what it's been thru. The dealer basically said that they believe the cylinder walls are glazed and that it also needs rings. They said the common cause is someone running it without an air filter.
     
    Last edited: Sep 8, 2012
  4. John C.

    John C. Senior Member

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    Kind of sounds like a bunch of fertilizer is being pitched at you. If the machine needed rings you would have had to add oil already. The engine would be hard to start in the temperature range of 70 degree F. or less. You would have high crankcase pressure that would tend to want to blow the dipstick out of the tube when you were running hard. Glazed cylinders happen when the piston rings don't seat on the cylinders. A dusted engine doesn't have a glaze problem. The dust is abrasive and mixes with engine oil to actually grind material off the cylinder walls.

    The other issue is rebuilding any engine for $1,500 sounds like a big bait and switch. Around here standard labor is around $1,000 a day. No one I know can rebuild an engine in a day and a half and make it better than when it was pulled from the machine.

    Make sure your air filters are clean, maybe check turbo charger boost pressure, take an oil sample and have it analyzed. From what you are describing, it doesn't sound like you have a lot of issues with just running this machine until more evidence shows up indicating a bad motor.
     
  5. motochris

    motochris Active Member

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    Thanks for the input. The rings/glazing is what the closest Bobcat dealer told my buddy.. and charged him a buttload to diagnose. All the injectors have been replaced, the pump and he had head the head redone (basically he kept throwing money at it), and the smoke still persists. That's when he decided to take it the closest dealer 100 miles away.
    The rebuild quote is reasonable if it's not being done by a $150 per hour dealer. The quote came from a friend who owns a local machine shop and includes pistons, rings, bearings, gaskets and labor. Heck, you can buy a rebuilt long block from a number of online sources for about $2500. I'm comfortable with the rebuild figure he gave me as being legit.

    The machine isn't turbocharged, so that's out the window. I do plan on getting an oil sample next and see what it says/means. I believe the oil was changed just recently however... should I run it longer before taking a sample?
     
  6. motochris

    motochris Active Member

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    So here's a couple pics of the smoke. This is at startup, maybe 1/4 throttle or so. It was a bit hard to get pics of since it's not dark or real heavy. It's a whitish/blue color.
    It goes away pretty much completely when warmed up as long as it's not over about 3/4 throttle or so. I have run the machine lightly, never really needing alot of throttle, so once warmed up I really don't see any smoke.
    In taking pics yesterday.. there was nothing to take a pic of once warmed up until I got over about 3/4 throttle.. then it was similiar to what is in these pics... maybe a bit less though.


    042.JPG
    043.JPG

    Here's some info I found online--

    Blue smoke is an indication of oil being burnt. The oil can enter the combustion chamber for several reasons.
    Worn valve guides or seals

    Wear in power assemblies (ie cylinders, piston rings, ring grooves)

    Cylinder glaze

    Piston ring sticking

    Incorrect grade of oil (eg oil too thin, and migrating past the rings)

    Fuel dilution in the oil (oil thinned out with diesel)

    At cold start, blue smoke is often evident, and can reflect reduced oil control, due to fouling deposits around piston rings or cylinder glaze (which is actually carbon deposited in the machined cylinder crosshatching. These tiny grooves actually hold a film of oil, which in turn completes the seal between the combustion chamber and the oil wetted crankcase). Blue smoke should not be evident at any time, but it is worth noting, that engines with good sound compression can actually burn quite a lot of oil without evidence of blue smoke. Good compression allows oil to burn cleanly, as part of the fuel. It’s not good though!

    --------------------------------------------------------------------------------
    White smoke occurs when raw diesel comes through the exhaust completely intact and unburned. Some causes of this include…
    Faulty or damaged injectors

    Incorrect injection timing (could be a worn timing gear or damaged crankshaft keyway).

    Low cylinder compression (eg caused by leaking or broken valves, piston ring sticking, cylinder and/or ring wear, or cylinder glaze)

    When white smoke occurs at cold start, and then disappears as the engine warms up, the most common causes are fouling deposits around piston rings and/or cylinder glazing.
     
  7. KOENIGS

    KOENIGS Member

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    I have seen a few Bobcats that the "Operators" had run them at 1/2 - 3/4 throttle and got significant carbon buildup. They are made to be run at or near full throttle. It's unlikely that you will cause any damage using the machine. I would run a can or SeaFoam through it and see if it eliminates most or all of the symptoms... if it is infact carbon based it very well may. Ron
     
    Thughes likes this.
  8. motochris

    motochris Active Member

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    I wasn't aware of that... This is the first I've had/used one. I'll start using it with considerably more throttle and see what happens.
     
  9. Scrub Puller

    Scrub Puller Senior Member

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    Yair . . . KOENIGS.

    .

    Who says? Why? Where is the "significant carbon buildup" and how does it cause smoke?

    Just asking.

    Cheers.
     
  10. KOENIGS

    KOENIGS Member

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    Bobcat... And most other manufacturers. That is where the engines make Power, where the cooling system (Engine, hydraulic or otherwise) is intended to work, and where the Hydraulic Pump(s) is set to work most efficiently. Carbon deposits on pistons, namely ring lands can and do cause smoking.
     
  11. motochris

    motochris Active Member

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    I figure it's certainly worth a shot to try. Since this was a rental at one time, I'm willing to bet it's had plenty of running at partial throttle. Guys like ME who have little skidsteer experience.... running it at lower throttle settings so the machine is smoother. Let's you "ham-fist" your way around with less jostling. :)
    If I try an additive/flush like Seafoam... how many hours would you say it should be run?
     
  12. John C.

    John C. Senior Member

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    Actually what you are seeing is pretty normal. I went through this for years with true Komatsu engines. They smoked blue for the first ten minutes or so and then cleaned up until the next cold start up. What I saw was when the injection pressures went up into the 3,000 PSI or higher range and at the start up temperatures all the fuel didn't burn completely. Check your oil consumption over a hundred hours or so and I'll bet you have nearly none.

    You can lose a lot of sleep worrying about something that is pretty normal.
     
  13. motochris

    motochris Active Member

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    I have a Kubota tractor that does the same basic thing... but since it's ran forever that way, I never worry about it. Only reason I was at all concerned about this is that my buddy was... and he knows more about these things than me.
    I may still try some Seafoam and change the oil again in a while to see if it helps. If I don't have any real issues... I'll most likely just keep using it like it is.
     
  14. motochris

    motochris Active Member

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    OK... my buddy just walked in with the paperwork from the dealer he took it to. Now I know alot more.
    You can see by the invoice..... low compression readings on all cylinders, especially with cyl. #2.
    I'm still thinking I'm gonna run it a while though.... what do you guys think NOW?

    038 (3).jpg
     
  15. John C.

    John C. Senior Member

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    Was that compression test done before or after the head was repaired and the injectors replaced?

    Basically there should by two reading on a compression test. The first is done dry and the second is done with a shot or two of oil in the cylinder. If there is a difference it could indicate rings. If there is no difference then you usually have a valve problem. If they had the head off they would have known for sure whether or not the engine was dusted.

    What you are telling us doesn't make sense at this point.

    As before, run it and see.
     
  16. motochris

    motochris Active Member

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    Makes sense to me... the injectors, pump and head were all redone at a local shop, THEN it was taken to the dealer that did the tests shown on the invoice above. Among other things, they did 2 compression tests, one dry with the lower readings as listed on the invoice (#1-300psi, #2-260psi, #3-360psi, #4-365psi) and one with oil with the higher readings (#1-420psi, #2-320psi, #3-440psi, #4-480psi)also listed on the invoice. The higher reading indicated the head was good, the rings were the most likely culprit.
    Am I missing something that leads you to believe something different?
     
    Last edited: Sep 11, 2012
  17. John C.

    John C. Senior Member

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    Those reading don't make and sense at all.

    You might see thirty to forty PSI difference after a squirt of oil but certainly not 120 PSI that shows in #1 cylinder and 115 PSI for #4 cylinder.
     
  18. motochris

    motochris Active Member

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    Ok... so what do you suppose is happening here then? Fictional results? Unusual circumstances?
    I've seen 75+ psi jumps on worn gas motors, though I've never tested a diesel.
    Anyone else have input on this?
     
    Last edited: Sep 11, 2012
  19. mitch504

    mitch504 Senior Member

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    If those compression figures were right, this thing would be hard to start.

    I would be completely unconcerned about this little bit of smoke if the machine ran good.

    If we are all wrong, and it does need rings, it'll still need rings after you run it a few years.


    Run it and stop worrying!
     
  20. motochris

    motochris Active Member

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    Oh, I definitely plan to use it. :)
    I'm actually not too worried at all, I just figured IDE ask to make sure I wasn't going to do something stupid. ***
    Thanks!