Forum Thread

Small engine continually leaking oil?

Dr. J 25,043 3,353 September 23, 2015 at 09:31 AM
I have several small engines at home. For some reason the two that are on generators have slow continual leaks. I first noticed it when I brought home a ~ 18 yo generator (was Dad's until he passed away 12 years ago and it's been sitting in a garage since). The thing was bone dry. filled it with 5W30 synth (per the manual) and it ran fine (after also cleaning carb).

It's been sitting in my garage for a couple months and I noticed oil stains on the floor from the generator. Then I looked over at my generator a few ft away (about 4 yo) and it, too, has some leakage.

Both are B&S engines however I have B&S engines on other equipment but this issue does not come up.

So - is this normal - how to limit it? As best I can tell it looks like the oil is coming from the fill spout and neither is/was overfilled. FWIW these are both "fill till spills" models without level sticks.

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#2
There is no such thing as a fill till spill. In the operating instructions / service manual / stamped somewhere, is a recommend quantity.

This allows some breathing space for the oil as it expands when heating up in the summer. If you "fill till spil" the expanding oil has nowhere to go but the breather. I know you said it was not overfilled but I think it was.

Remeber the engine has a sump filled with oil which you also need to account for. Hope you come right
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#3
Ya I would agree there definitely is a quantity of oil the engine is supposed to have. Worth looking into again to make sure you don't have too much in it. Remember your not likely to empty it 100% on a change.

As for the old engine it's very likely the seals have dried up. I have had decent luck running a high milage oil specifically valvoline maxline in cars and small motors that have small oil leaks either slowing it down or stopping it.
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#4
there is no dipstick on either machine:

http://www.briggsandstratton.com/...o-dipstick

Either of the yellow oil fills may be used to fill the engine with oil as they both lead to crankcase. Add oil until it reaches the top threads of the oil fill hole.

No insult but I am surprised neither of you have ever seen this.
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Last edited by Dr. J September 23, 2015 at 04:24 PM
#5
dry oil seals or you need to use regular oil. this 18 years old machine, are sure it states synthetic oil not regular oil?
i have older lawn mower smokes on synthetic oil and runs clean on regular.

oil until it reaches the top threads of the oil fill hole --- it's like rear differential in car , you do not have dipstick on top just hole on side, i have the same setup on edge cutter.

with 18 year engine you need to get new seals.
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Last edited by dude2000 September 23, 2015 at 05:44 PM
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#6
Quote from dude2000 View Post :
dry oil seals or you need to use regular oil. this 18 years old machine, are sure it states synthetic oil not regular oil?
i have older lawn mower smokes on synthetic oil and runs clean on regular.

oil until it reaches the top threads of the oil fill hole --- it's like rear differential in car , you do not have dipstick on top just hole on side, i have the same setup on edge cutter.

with 18 year engine you need to get new seals.

B&S just gives recommendations on operating temp; synth 5w30 had the widest range so that's what I used.

Also while the 18yo engine is the worst, the newer engine also leaks to a lesser extent.
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#7
Clean it with degreaser and let it run for sometime. You may see a trace of oil.
Oil can leak because
Stuck float in carburetor and gas gets in to engine.
Cracked engine block
Bad gasket
Bad seal
Wrong oil viscosity.

I am using 5w-30 in my car as winter oil because it could get really cold in IL.
First number is only important during cold start and first 3 minutes, till engine starts warming.
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#8
Synthetic oil has smaller molecules than conventional oil. If the engine was run for years on conventional oil, you should continue to run it on conventional oil.
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#9
Quote from VorlonFrog View Post :
Synthetic oil has smaller molecules than conventional oil. If the engine was run for years on conventional oil, you should continue to run it on conventional oil.
This actually is a myth. You can interchange synthetic and natural at will and even mix them.

Are you sure it isn't the generator oil you are looking at? Those typically fill to the bottom thread as well and are designed to be used as the generator runs. Is it leaking or just using a lot of oil? A leak you should be able to find and fix with a new gasket (hopefully).
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#10
Quote from VorlonFrog View Post :
Synthetic oil has smaller molecules than conventional oil. If the engine was run for years on conventional oil, you should continue to run it on conventional oil.
Quote from dealgate View Post :
This actually is a myth. You can interchange synthetic and natural at will and even mix them.
Provided the rubber seals are in good shape. I switched my Nissan to 10W-30 synthetic, and in a few days it was dripping maybe a couple of teaspoons a week, but within days of changing back to conventional 5W-30, the drips completely stopped. Valvoline said it was because synthetic was slipperier. I had more synthetic left, so I mixed a little of it with conventional, and the Nissan didn't leak with 25% synthetic.
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