Briggs & Stratton Vanguard Oil Leak

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  #1  
Old 02-23-09, 05:37 PM
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Briggs & Stratton Vanguard Oil Leak

I have a 16 HP V-twin vertical shaft B & S Vanguard engine (303777) on a Simplicity tractor. Lately I notice oil on the garage floor after I've used the tractor for snowblowing. It's not much (no more than a teaspoon I'd say) but it appears every time after I use it. I pulled off the air cleaner cover and the two air filters. There's just a very small amount of whitesh emulsified oil on the bottom of the air filter gasket. There's certainly no oil running out of the air filter assembly onto the tractor so a malfunctioning breather is not the cause of my problem.

Because of the tractor frame I cannot look up at the bottom of the engine. The oil is distributed over a fairly wide area on the bottom of the tractor frame, almost like it's been blown there. It seems to be centered sort of between the two cylinders and the crankshaft. It's more on the side where the starter motor is, not the side where the oil filter is. I removed some of the sheet metal shrouding. There's no oil I can see on the cylinder head fins. The valve covers are tight and I don't see any oil leaking from them.

So that makes me wonder if the bottom main oil seal is bad. If I believe the hour meter the engine only has 230 hours on it. I'm inclined to believe it because the tractor is in great shape (I bought it used). There's virtually no wear on the brake pedal, the seat has no tears or cracks, the starter motor gear has very little wear, etc.

What other sources of an oil leak should I check for? If the bottom main seal is bad (is that common?), do I need to tear down the whole engine to replace it? I don't yet have a repair manual for this engine so I don't know what is required to replace the oil seal.
 
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  #2  
Old 02-23-09, 07:08 PM
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Most of the oil leaks I see are coming from the drain plug area or the oil fill tube where it meets the engine. Check these areas over well. It could be the crankshaft seal, but usually not. Usually when the crank seal leaks, it runs down and pools up in the top of the pulley on the shaft. Then, when you start it, all that oil slings out under the mower and makes a mess. This doesn't sound like what is happening.

If it is the crank seal, it generally doesn't take engine removal to repair, but it may in some cases. It doesn't require engine disassembly to fix.
 
  #3  
Old 02-24-09, 03:37 PM
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Missing O-ring

I agree it doesn't seem like I have a bad crankshaft seal--I looked for an oil-sling pattern around the top pulley and don't see anything. The oil drain is a beefy extended steel pipe with with a big hex cap nut. I can't see where it enters the engine block but everything seems tight and solid. Then I checked where the plastic oil filler enters the block. It sure looks like that's my problem. That location would also explain why there's oil on the bottom of the starter motor since it's right next to oil filler tube.

I pulled out the oil filler tube and inspected it. I don't see anything wrong. The O-ring looks OK and I don't see any cracks in the plastic. I bought a new O-ring anyhow and replaced it. When I was putting it back I noticed a groove inside the dipstick cap where it looks like there should be an O-ring, but there's not. I found an exploded engine diagram on the web and indeed there should be an O-ring there. So obviously I'm not getting much of a seal. No oil comes out there since it's 6 or 7 inches above the oil level. But I'm wondering if that could be the cause of my problem. What is the purpose of that O-ring--an oil seal or an air seal? What happens when it's not there?
 
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Old 02-24-09, 06:14 PM
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You did not list an engine Code Number so I will guess it may be covered in the Illustrated Parts List below. On page 2, you will see Crankcase Gasket Ref. No. 12. This is another possible area for the oil leak origin. Leaks coming from the joint formed by the sump and cylinder assembly are not uncommon. Identifying the area the leak is coming from is difficult. Occasionally, tightening the bolts securing the sump to the cylinder assembly will stop the leak. Replacing the crankcase gasket is actually not difficult. If you need to replace the gasket post back for tips/advice.

Is the O-ring you are referring the top one. This O-ring is important to prevent oil from blowing out of the oil cap, which normally is not a problem unless you have an increase in crankcase pressure, which is common with cylinder/ring wear.

http://www.briggsandstratton.com/pdf...100/MS9727.pdf

To find the leak you will need to clean the engine, run it and inspect for leaks. Sounds easy but is time consuming.
 
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Old 02-24-09, 07:28 PM
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Engine model # is 303777, type is 1111-A1, code is 96112011. I looked at the same exploded parts view as the one you provided in your link and that does seem to be the correct one. I see the gasket you reference. It's not clear from the diagram but I assume those bolts thread from the bottom upward--correct? I can try locating them (without removing the engine from the tractor) and seeing if any are loose.

Yes, the missing O-ring is the top one. I will replace it but I don't really see where oil has been blowing from the top of the oil filler tube. It looks, at first blush, to be coming from the bottom. But there was all kinds of oil-soaked grass debris in that area so I can't be certain of that.

I cleaned up the lower portion of the engine and will run it to see if I can find exactly where the oil is coming from. I've tried this before and agree that it is not easy. Is it possible to purchase UV dye and get a UV light to track down the leak if I can't find it visually? What can I expect to pay for this?
 
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Old 02-24-09, 07:47 PM
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As the oil that is soaked in the grass/dirt/dust caked up on the engine warms up, it will drip even if the leak is stopped. I'd suggest cleaning the engine. Pick up a degreaser like "purple stuff" from an auto parts store and clean the area with the degreaser and a hose sprayer or better yet, a pressure washer. This way it will be clean and you will be able to see a fresh oil leak, and you won't be wondering if the oil dripping is from the caked up mess or an active leak. Then run it and see if your leak has stopped since you replaced the gasket at the filler tube.

The o-ring missing at the dipstick creates an air leak into the engine, which increases crankcase pressure and basically renders the PCV system inoperative. This will cause the internal pressures to push oil out of places it normally wouldn't. Replace this, and I think you have a pretty high chance of having your leak stopped.
 
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Old 02-25-09, 07:54 AM
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Originally Posted by BikerBill View Post
I looked at the same exploded parts view as the one you provided in your link and that does seem to be the correct one. I see the gasket you reference. It's not clear from the diagram but I assume those bolts thread from the bottom upward--correct? I can try locating them (without removing the engine from the tractor) and seeing if any are loose.
The parts list is correct for your engine.

The bolts are installed from bottom up and you should be able to access each of them with engine installed.

Originally Posted by BikerBill View Post
Yes, the missing O-ring is the top one. I will replace it but I don't really see where oil has been blowing from the top of the oil filler tube. It looks, at first blush, to be coming from the bottom. But there was all kinds of oil-soaked grass debris in that area so I can't be certain of that. I cleaned up the lower portion of the engine and will run it to see if I can find exactly where the oil is coming from. I've tried this before and agree that it is not easy.
Definitely replace the O-ring. If oil were coming from the cap, I think it would be evident. The missing O-ring in the oil tube can cause a loss of crankcase vacuum allowing oil to enter the air filter. If this is happening you will see oil in the filter area.

To find the source of the leak you need to start with a very clean engine. The leak could be anywhere. I have been fooled more than once thinking a leak originated in one place and actually came from a different place. Ensure the oil is not overfilled.

Originally Posted by BikerBill View Post
Is it possible to purchase UV dye and get a UV light to track down the leak if I can't find it visually? What can I expect to pay for this?
I have used an oil dye and black light in the past as an aircraft mechanic to locate source of oil leaks. I have no idea of the cost and do not think it is needed in your situation. I think starting with a thoroughly clean engine is the best way to approach this. If the leak is minor, it may require an hour or so of running before the leak shows up.


When oil leaks are caused by excessive crankcase pressure a crankcase vacuum test is performed. I doubt you need to do this.

Here is an article about making a homemade manometer:
PER Notebook - Those Messy Oil Leaks

Begin at page 127 in this manual:
http://www.fastonline.org/CD3WD_40/JF/417/06-247.pdf
 
  #8  
Old 02-27-09, 12:21 PM
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Some New Information

It turns out that the top O-ring on the oil filler wasn't missing after all. In the process of installing the new O-ring I realized this O-ring doesn't mount in the annular groove on the inside of the dipstick cap itself, rather it mounts on the outside of the molded plastic filler tube. And there was an O-ring already there. Black rubber on black plastic--I just didn't see it. I replaced it anyway.

I also noticed that my oil level is high. It's about 3/8 of an inch above the top line that marks the "normal" zone. I don't know how this happened. When I changed over to winter oil last fall I didn't change the filter so I made a point to add less than the specified amount of oil. Maybe I still overdid it. Anyway, the level is too high. How could this contribute to my oil leakage problem?

After I restore the oil level to the "normal" zone, I'm going to clean up the lower portion of the engine as best I can, fire it up, and see if I can find the source of the leak.

If I need to measure crankcase vacuum I already have an analog dial-type manometer that I use on my propane house furnaces.
 
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Old 02-27-09, 04:03 PM
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Ok, the high oil level brings a new aspect to this. Smell the oil...does it smell like gas? Is it thin oil? If so, your carb is leaking gas into the crankcase and diluting the oil.
 
  #10  
Old 03-01-09, 07:31 PM
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I drained about 6 ounces of oil from the engine to bring the oil level down to the top of the "normal" zone. I didn't smell any gas in it and the viscosity seemed the same as some fresh oil I had in the garage. I've cleaned up the engine and the tractor frame where the engine mounts as best I can. We have 9" to 15" of snow on the way so I'll get a good chance to see what the oil leakage under load picture looks like in a day or day and a half. I will post back.
 
  #11  
Old 03-04-09, 08:31 AM
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Update

OK. I ran the tractor/snowblower for an hour and a half. Afterwards I placed a piece of clean cardboard under the tractor. I checked many hours later and had one drop of oil on the cardboard, directly underneath the hex oil drain cap that attaches to the angled iron pipe coming out the base of the engine. But the pipe itself seemed dry. Then we got a bonus snowfall overnight so I ran the tractor/snowblower for another hour. This time no oil leaked onto the cardboard. I carefully checked the engine and tractor deck where the engine mounts. There was a small amount of oil on the tractor deck that seemed to be coming from one the four ears or lugs that hold the engine down. It was not enough to reach any of the drilled holes in the deck so nothing dripped down. The area around the plastic oil filler was definitely dry, as was the seam where the oil sump casting meets the engine block.

I ordered a B&S repair manual for this engine. When I get it I will remove the shrouding that covers the area where the oil drain pipe screws into the engine, even though that's not near the mounting lug where I saw the oil. That will also allow me to better clean up the side/underside of the engine. Then I'll run the engine again and look for any leakage.
 
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