Diesel engine blow by

   / Diesel engine blow by #1  

Scott037

New member
Joined
May 18, 2004
Messages
5
Location
Southern CT
Tractor
Kubota B21
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? /forums/images/graemlins/confused.gif
 
   / Diesel engine blow by #2  
</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
 
   / Diesel engine blow by #3  
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
 
   / Diesel engine blow by #4  
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.
 
   / Diesel engine blow by #5  
Could easily be the brand of oil you are using too.

A full synthetic with low <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.
 
   / Diesel engine blow by #6  
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.
 
   / Diesel engine blow by #7  
I wonder if you have an injector hanging open or leaking slightly, diluting your oil?
 
   / Diesel engine blow by
  • Thread Starter
#8  
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!
 
   / Diesel engine blow by #9  
</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>

/forums/images/graemlins/shocked.gif Slow down there. /forums/images/graemlins/shocked.gif

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.
 
   / Diesel engine blow by #10  
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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