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randywatson
Join Date: Apr 2007
Posts: 109 texas
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2008-01-30          150953


looking for any possibility on cause of oil blow by out the valve pan vent on b7100 with 820 hours at high rpm blowing snow,

Ive thought of Rings, valve adj, valve stem seals, anyone else got any ideas?




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BillMullens
Join Date: Jun 2000
Posts: 649 Central West Virginia
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2008-01-30          150955


The usual answer is rings or cylinder wall problems.

Get a leakdown test and go from there. That is low hours for that kind of thing to be happening.

Edit: Also a problem with the crankcase ventilation system, such as the PCV valve if there is one, could give the appearance of excessive blowby. That is what the books say, it has been my experience it is never that easy.

Good luck,
Bill ....


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hardwood
Join Date: Dec 2002
Posts: 3583 iowa
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2008-01-30          150965


Randy; Does this happen mostly in the winter? Does the tractor sit for long periods between useages? You really don't have enough hours to think about something major. I had a Case 1070 100 hp farm tractor that I used during the winter for snowblowing only. It would sit in the shed without use between snowstorms, sometimes a month or more. It would show the same symproms as your tractor, otherwise it started and ran fine. If you are seeing vapors,(steam) and drops of oil hanging on the end of the blowby tube, theh I think you are seeing, as I was, water being being evaporated out of the crankcase during extended operation when you engine is getting fully warmed up and it tends to carry some oil vapors with it that condense toward the bottom on the inside of the tube and drip off the end. Frank. ....


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randywatson
Join Date: Apr 2007
Posts: 109 texas
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2008-01-30          150971


Hardwood, thanks, although It is not my problem but was on another site I am monitoring,

the original post states mid 80's used for mowing and snow blowing, oil out tube after warm up, no other symptoms,

further question by me he said he had maintence 2x annual, and the 820 hrs.

he did not spec how much oil, but indicated full on startup, and still in range when he noticed the oil,

I will try and pin him down on how much oil lost,

if a few drops, and since no other symptoms stated, I agree with you, will let you know what he says.

....


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Art White
Join Date: Jan 2000
Posts: 6898 Waterville New York
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2008-01-31          150995




I'd say that it might have the cylinders glazed. The best that could be done is to put it under high load for at least ten straight hours if possible. That doesn't mean just high throttle but high load too. We get to see it from time to time in low houred use where an engine doesn't get up to proper operating temps and the fuel that is unburnt glazes the cylinder walls. ....


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candoarms
Join Date: Mar 2007
Posts: 1932 North Dakota
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2008-02-01          151000


Randywatson,

If I'm understanding you correctly, the problem has to do with oil escaping from the valve cover vent?

If this is true, I would rule out any problem with the rings, cylinder walls, or any compression problems. The problem, if there is one, would be in the top end of the engine. (possibly valve stem seals) The lower end of the engine (crankshaft, rods, pistons, rings, etc) is probably fine.

I'm guessing that there really is no problem at all.

A little bit of oil residue appearing on the valve vent is common in cold weather. First off, the oil is extremely thick in cold weather. This causes the oil to build up a bit in the valve cover, because it can't drain back into the oil pan as rapidly as it does when it's warm.

Additionally, the expansion of the air contained in the valve cover, due to heating, causes a great amount of air to be expelled from the valve cover as the engine begins to warm up. Combined, these two things will cause some oil to be purged from the valve cover vent.

A possible solution to this problem would be to use lighter engine oil during the winter months (drains back to the oil pan quicker when cold), coupled with engine preheating. A heated garage works best.....but any heat source that brings the engine up to room temperature is better than starting an engine when it's very cold.

Joel ....


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BillMullens
Join Date: Jun 2000
Posts: 649 Central West Virginia
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2008-02-01          151003


Quote:
Originally Posted by candoarms | view 151000
I would rule out any problem with the rings, cylinder walls, or any compression problems.The problem, if there is one, would be in the top end of the engine. (possibly valve stem seals) The lower end of the engine (crankshaft, rods, pistons, rings, etc) is probably fine.


I disagree. Problems with the rings or cylinder walls allows pressure into the crankcase. This pressurizes the valve cover via the pushrod tubes,etc. Valve seals are not meant to control pressure, only oil flow. Same is true of valve guides. If the valves aren't seated properly or there are valve or valve guide/seal problems, there would be different symptoms.

Traditionally, blowby=ring problems.

However, I may still agree that there isn't really a problem. All engines have some blowby, it is just a matter of how bad is it. If the crankcase ventilation system (such as PCV valve) can't handle the blowby, it is deemed excessive.

A leakdown test will give a definitive answer on the condition of the rings & cylinders.

Bill ....


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randywatson
Join Date: Apr 2007
Posts: 109 texas
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2008-02-01          151008


Bill, Joel, Art, Frank,

thanks for the input, I told him I was consulting the experts, and copied and pasted this tread to the other site thread so I would not leave out anyones advise,

fall a year ago My B7100 that had been getting harder to near impossible to start started blowing bad (spewing) while I was doing some blading on the driveway in hot weather, since It was a rental before I owned it, and I had no idea how many hours was on it, I immediately went to the rebuild, man it needed it, now it runs like a champ.

Thanks againg, will let everyone know if I hear how he resolves the situation. ....


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