OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Tecumseh / Kirby Engines 12 hp OHV Tecumseh blowing oil into air cleaner

Hi All;
I have a 12 hp Tecumseh on a Victa ride on and it's giving me nothing but grief ( I guess that's why the previous owner sold it!).
I thought I had everything that could possibly go wrong sorted and finally got it running but it had me well fooled.

It now pumps copious amounts of oil out of the breather pipe into the air cleaner when it warms up. It looks like it would pump itself dry of oil if I let it.
What would be causing this and how can I fix it?

The previous owner said he had done a valve grind, fitted new gaskets, new rings etc after replacing a dropped rod.
When it wouldn't start for me I checked the valve clearances and the exhaust was at 25 thou!
I reset them at 6 thou and (after I also replaced the broken flywheel key)it started ok.
I pulled the bottom end off (while trying to find the cause of the starting problem) and all looks well but I haven't had the head off it.

Any help would be much appreciated.
Best regards.
Rob.

There are two common causes of oil passing through the breather. The first is over-filling the sump with oil. The second is combustion gas getting into the crankcase under pressure. There are three ways gas can get past the piston: a hole in the piston, piston rings not sealing to the cylinder bore, or in the case of OHV engines, a blown head gasket.

I suggest you begin by checking the oil level, and verifying that you haven't been trying to run the machine on a slope of greater than 15 degrees. If that doesn't provide the answer, a compression test may be useful, but probably won't in this case if the previous tenant actually did replace the piston rings. If he didn't replace them, you'll probably find that the compression pressure rises substantially when you put a spoonful of engine oil in through the spark plug hole and repeat the test. This would mean that the piston rings are not sealing to the cylinder bore.

If it should turn out that the oil level is correct, you haven't been operating on a steep slope, and the compression pressure does not change much when you put oil in the cylinder, the remaining strong possibility only applies to OHV engines like yours: the head gasket may be blown to the pushrod cavity, which pressurises the crankcase and has the same effect as blowby passing the piston rings.

Please let us know what turns out to be the problem, or ask further questions if necessary.

First off, thank you for your prompt and detailed answer to my cry for help.
Oil level and sloping ground were easy to cross off the list.
I don't (yet) have a compression tester so I couldn't do that.
I took the head off and the, very thin, steel head gasket look fine.
The piston looks fine, no holes. I haven't yet taken it out so I don't know if the rings have been installed correctly.
When I took the breather assembly off I noted that it had been installed with the reed valve(?) at the bottom. Is that the correct way to install it? I thought that, if there was to be any level of oil in the chamber that valve should most likely be at the top.
Is this just wishful thinking from a poor soul who really doesn't want to completely pull the engine down?
I have (I hope) added photo's of head, gasket, piston top and breather assy as it was installed.




Thanks again.
Rob.

Rob, I'll refer to the Tecumseh engine and transmission manual (a 1,400 page document available in the Manuals section of this site).

The manual describes the type of breather you have as a "side mounted breather", and indicates it installs with the large port and the reed toward the top, so the tiny drain holes are in the bottom, for obvious reasons.

That may well be the answer to your problem, as you suggested. Just check that the tiny drain holes are in the bottom horizonal surface of the breather, not the top.

Here are a couple of excerpts from the manual about trouble-shooting for oil passing through the breather - note the emphasis on installing the valve with the drain holes facing down:
The Breather is a sealed assembly. If it is defective, replace the entire assembly. The rubber tube on the outside is not part of the assembly. Install the breather with the drain holes toward the base of the engine. Always use a new gasket. The retaining screws must be tight.
If oil is being pumped out the breather:
1. Check for excess speed.
2. Operating at excessive angles.
3. Loose oil filler cap.
4. Worn rings.
5. Excess blow-by.
6. Breather body installed up-side down.
7. Overfilled with oil.

All of that is standard stuff, except the warning about the loose filler cap.

Here is another troubleshooting guide for breather oil from later in the manual:
BREATHER PASSING OIL
1. Check the oil level, make sure the engine is not overfilled. Also verify that the viscosity rating on the container of the oil being used is to specification.
2. Check the angle of operation. Avoid prolonged use at a severe angle.
3. Check the engine R.P.M. setting for excessive R.P.M. using a vibratach or other tachometer and compare it to the R.P.M. settings found on microfiche card # 30 according to the engine model and specification number. Adjust the high and low R.P.M. as necessary.
4. Check for leaking or damaged gaskets, seals, or "O"-rings. External leaks may not be evident; however, the leak may prevent the engine from achieving a partial crankcase vacuum.
5. Check the breather for damage, dirty condition, or improper installation. The oil return hole(s) must face down.
6. Check the engine compression using a compression tester. If the engine has weak compression, determine the cause of weak compression: worn rings, leaking head gasket, or leaking valves. Follow the compression tester's procedure.

Fixed!
Thank very much for your help.
The breather assembly being installed upside down seems to have been the culprit!
Such a simple error but so much anguish! A lesson well learned!
The old woodworking adage of "Measure twice, cut once" springs to mind.
The previous owner, a mechanical novice like me, managed to install a conrod, install a set of rings, do a valve grind and put the engine back together but all this good work was brought undone by a simple error.
Thanks again for your help.
Rob.

Thanks for reporting back, Rob. The error lies predominantly with Tecumseh - it is not normal engineering design process to have parts that can just as easily be installed backwards, but cause problems if that happens. There should be, and normally is, either an assymetrical mounting so it would only go on one way, or the word "Top" pressed into the component to show which way it goes.

I will close this thread - if any member has something to add to it, please PM a moderator.