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Oil coming from crank case vent to air-cleaner


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03-07-04, 07:33 PM   #1  
mikeymcse
Oil coming from crank case vent to air-cleaner

I have a 17HP Craftsman lawn tractor. It smokes (blue white smoke) when it has been running for a while. I found oil pumping out from the hose running from the crank case to the air breather. This engine has no PCV valve. What can cause oil to pump from the crank case? How do I fix it?

 
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03-07-04, 08:58 PM   #2  
Hello: mikeymcse

Couple of things come to mind.

Over filled crankcase. Too much oil.

Blow by caused by worn rings.

Worn valves or vave stem seals, etc.

Engine may be running too hot.

Do a compression test. Remove spark plug, hold throttle wide open and crank the engine. Only one compression hit. That number on the gauge is the compression ratio.

Reason the smoke appears when the engine has ben running for awhile, is heat expansion. Cyclinder walls expanding away from worn rings which cannot expand any further to prevent compression loss.

Most likely I haven't covered all of the possibilities. The other resident small engine service and repair professionals in the forum may be able to offer additional suggestions, advice & help.

Check back on your question several times over the next few days for additional replies.

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03-07-04, 09:02 PM   #3  
Did you ever tip over this mower to get under the blade housing? If you did and it was tilted toward the direction of the carb to long, oil could have run into the carb.
Anyway, I can tell you how to correct this but it does not mean it will not do it again depending on what your answer is for my above question. The first thing you need to do is take your carburetor off of the engine, and open it up and clean every nook and cranny including jets float needle valve seat. Every thing on there really well. To get it clean well use gumout spray along with a soft tiny clean brush or clean cloth/rag. After cleaning everything really well, install the carb back onto the engine. Do not start the engine yet. Remove the air filter and replace it. Most likely you have oil in it. After doing that it would also be a good idea to replace the sparkplug. After doing that drain all of the oil out of the engine, it is probably contaminated with gas. After doing that replace with the recommended oil for your engine. Usually it is "SAE 30" After doing all of that, then you can start the engine and it should run like a charm. After you are done with all of this let us know how it goes! Cheese will most likely give you some great information as well!

 
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03-08-04, 12:27 AM   #4  
Hello mikeymcse!

What brand engine do you have? One cylinder or two? Check the oil. Is it too full? Does the oil smell like gas? Could be gas-thinned oil, too full of oil, bad rings, bad breather, too hot, bad cylinder, etc...


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God bless!

 
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03-10-04, 06:38 PM   #5  
mikeymcse
Thanks for all the suggestions. To answer your questions the engine is a single cylinder B&S, the mower has not been tipped over and I don't smell gas in the oil. The oil level is okay.

The suggestions about blow-by seem likley since the oil is spurting all the time from the hose running from the crank case to the breater . I'll check the compression and if it is low pull the head and check the valves, valve stem seals and rings.

Thanks for all the help
Mikeymcse

 
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03-10-04, 08:42 PM   #6  
Just let us know if we can help you further. As you diagnose your machine, please post your results so that Cheese may help you out.

 
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03-10-04, 10:25 PM   #7  
mikeymcse,

Your engine is overhead valve. On the OHV engines, a blown head gasket will cause excessive blowby. Check the head gasket carefully. If it looks like it may have been leaking between the cylinder and the pushrod chamber, then that's probably the problem. A bad crankcase breather is another good and easy place to look. If the valve in it is stuck or gummed up or has something in it, you'll get lots of blowby into the air filter housing.


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God bless!

 
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03-22-04, 06:02 PM   #8  
How did everything go with this? Were you able to remedy the problem?

 
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03-22-04, 06:37 PM   #9  
mikeymcse
Thanks again for the suggestions I am waiting for good weather before I start working on it. I have to do the work outside.

 
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03-22-04, 06:47 PM   #10  
Good Luck and have fun!

 
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