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  1. #1

    Join Date
    May 2004
    Posts
    5
    Location
    Southern CT
    Tractor
    Kubota B21

    Default Diesel engine blow by

    I have a kubota B21 backhoe/loader with 3 cylinder diesel with 1200 hours. From reading earlier posts I believe that the engine is experiencing some degree of blow by. I have started to notice slight "puffing" smoke coming from the vent tube, however, there is no sign of any oil leaking from the tube or engine. The engine doesn't smoke from the exhaust except for a puff of black smoke on start up.

    I don't experience any power loss while using the hoe, however the engine does bog down significantly with some smoking when I am using the FEL (even picking up light objects). I have also noticed quiet a bit of engine oil viscosity break down very quickly after a fresh oil change.

    My main question is will I do damage to the engine running it with this amount of suspected blow by as long as I frequently change the engine oil? Is this relatively normal, or should I be saving my pennies to get this in to the shop? [img]/forums/images/graemlins/confused.gif[/img]

  2. #2
    Super Star Member Egon's Avatar
    Join Date
    Aug 2001
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    18,061
    Location
    Nova Scotia, Canada

    Default Re: Diesel engine blow by

    </font><font color="blue" class="small">( engine oil viscosity break down very quickly after a fresh oil change. )</font>

    How do you tell this??

    Does the tractor use oil?

    1200 hours is not much time on the engine. My B7100 engine has always had a little blow by but uses no oil.

    Compression check may be the fastest method to get an answere.

    Egon

  3. #3
    Elite Member RalphVa's Avatar
    Join Date
    Dec 2003
    Posts
    4,003
    Location
    Charlottesville, VA, USA
    Tractor
    JD 1025, previously Gravely 5650 & JD 4010

    Default Re: Diesel engine blow by

    My old 1972 Benz with almost 200,000 miles on it started building up a little pressure in the crankcase, enough to leak a tiny bit of oil around the oil fill cap. Now, my 1983 Benz with almost that many miles is starting to show the same thing. They were/are tied into the suction line. Excess vapors go to the intake manifold. Both of these used some oil. Benzes are supposed to, up to a quart/500 miles. These both used a quart about every 2,000 miles. Oil was changed at 3,000 miles (at least before switching the present one to Mobil 1; will be 5,000 miles now).

    I'd try a different oil, maybe even a synthetic one. Could cause things to tighten up. Usually works on transmissions and power steering systems, not necessarily engines.

    Ralph

  4. #4
    Platinum Member
    Join Date
    Feb 2005
    Posts
    976
    Location
    Central WI

    Default Re: Diesel engine blow by

    I would do a compression or leakdown test and also test the injectors. A steady stream of vapor is expected with an older engine, but puffing typically indicates a problem with a single cylinder.

  5. #5
    Elite Member SkyPup's Avatar
    Join Date
    Dec 2003
    Posts
    3,005
    Location
    North Central, Florida
    Tractor
    Kubota L-39 GST TLB, Kubota L3130GST, Massey 1030 HST, Kubota ZD-21 ProDecK, Two Euro VW TDIs

    Default Re: Diesel engine blow by

    Could easily be the brand of oil you are using too.

    A full synthetic with low &lt;5% Noack volatility will produce allot less crankcase pressure than a lesser oil that loses 15% or more of its volume to evaporation at operational temperature.

  6. #6
    Platinum Member
    Join Date
    Sep 2004
    Posts
    583
    Location
    south/central Va.
    Tractor
    Deutz Fahr Agrofarm 100, Stoll loader, bucket, forks & root grapple

    Default Re: Diesel engine blow by

    Where is the vent pipe connected to the engine?

    I have a Fiat engine that's vented from the side cover under the head. I have a Perkins engine that's vented from the valve cover(on top).

    Both have vapors present. The Perkins has far more than the Fiat. Oil consumption is zero(I don't add between oil changes). The Fiat is 100 hr. oil changes and the Perkins is 150 hr's. at present with 200hrs. on the next change. I use 15w-40 Amsoil HD Marine Diesel syn. oil in both.

    When the humidity is high I see more vapor. It also seems the Perkins being vented from the valve cover has more positive pressure than the Fiat that's vented from a different area of the engine. I only see vapor from both. Not smoke. The Fiat has 1000+ hrs. on it. The Perkins is just under 200 hrs. (new engine) The vapor is normal for both engines.

    It has been my experience that vapors are normal. If you see drops of oil or blue smoke from the vent you then have a wear problem. If you want to see what's being vented hang a small container right under the end of the vent pipe. Do not block the vent pipe. Then check the container every 5-10-20 or what ever hours you like. If there's liquid being forced out of the pipe you can see what type liquid it is.

    I'll finish with I've seen engines run thousands of hours with even some oil smoke and drops of oil coming from the vent. Just have to keep the oil level topped off and remember to check it often. A little oil usage is cheap when you're talking about an engine rebuild or replacement. Just depends on how much power loss the engine has.

  7. #7
    Veteran Member
    Join Date
    Feb 2005
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    1,467
    Location
    Olathe, Ks
    Tractor
    Yanmar 1602D

    Default Re: Diesel engine blow by

    I wonder if you have an injector hanging open or leaking slightly, diluting your oil?

  8. #8

    Join Date
    May 2004
    Posts
    5
    Location
    Southern CT
    Tractor
    Kubota B21

    Default Re: Diesel engine blow by

    Thanks for all the responses. I am not experiencing any oil consumption, but when I check the oil after about 20 hours of use the oil just drips off of the dipstick like dirty water. When I rub it between my fingers, it doesn't feel like oil (doesn't seem thick and slippery) but more like water. I was concerned that it was being diluted by fuel.

    I wasn't aware that I could use a full synthetic so I will try that. Can I use a standard filter with a full synthetic oil? Seems someone told me (or scammed me) when I went synthetic in my truck that you have to use a filter rated for synthetic oils.

    Thanks for all the help!

  9. #9
    Platinum Member Av8r3400's Avatar
    Join Date
    Jan 2005
    Posts
    686
    Location
    North Central Wisconsin
    Tractor
    Kubota L3400DT

    Default Re: Diesel engine blow by

    </font><font color="blue" class="small">( I am not experiencing any oil consumption, but when I check the oil after about 20 hours of use the oil just drips off of the dipstick like dirty water. When I rub it between my fingers, it doesn't feel like oil (doesn't seem thick and slippery) but more like water. I was concerned that it was being diluted by fuel.)</font>

    [img]/forums/images/graemlins/shocked.gif[/img] Slow down there. [img]/forums/images/graemlins/shocked.gif[/img]

    Is the level of your oil <font color="red"> INCREASING </font> during the time between changes? Has your fuel consumption gone up? If you have a stuck injector, this could cause some $$damage$$ to your motor. I would investigate this further.

  10. #10
    Super Star Member Egon's Avatar
    Join Date
    Aug 2001
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    18,061
    Location
    Nova Scotia, Canada

    Default Re: Diesel engine blow by

    If the oil is becoming diluted with fuel [ Which it sounds like ] perhaps a real checkup is in order at a proper Doctors office.

    Egon

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