Kohler K301 high crankcase pressure, trying to diagnose with Leakdown test

[Alrashid2 355]

Hey yall. Started a discussion yesterday but I was going all over the place with ideas and it didn't gain much traction. To make a long story short, my Kohler K301 engine on my Wheel Horse 312-8 is having a high crankcase pressure, which is causing oil to push out of every gasket and opening on the front of the engine. 

 

What I find odd is that the breather seems to be in perfect shape and assembled correctly. Reed closes and sits flush, filter in good shape, parts in right order and direction. The gasket closer to the engine face does have a rip in it, however, it is compressing tightly and doesn't seem to be letting any air through... 

 

What's weirder to me is, if there is high crankcase pressure, why isn't it blowing air/oil out the breather valve? Instead, I have almost no oil leaking from the breather, but tons of oil leaking from the camshaft cover, governor bushing, and governor stop pin. Under load, the wet spots turned into a steady dribble and pool of oil after an hour of plowing.

 

I chatted with Lincoln over at AZ Tractors,he was very adamant that blowby from the piston rings would not cause oil to leak past gaskets. He said the Kohler engines will have oily, smoky exhaust so thick you can't even see through it far before the blowby causes oil leakage... He said if I'm not burning oil and no smoke, then he wouldn't be concerned with the rings at all. Likewise, I'm having trouble finding any post on here where oil leakage happens under load from crankcase pressure, but there isn't exhaust smoke from burning oil... 

 

All of this, paired with the fact that the tractor itself and the engine are otherwise in really great condition for being 40 years old, makes me think that my issue might not be piston rings. So I am trying to narrow down the list and check anything else that could be causing this... So far I have checked:

 

• Breather is correct and in good shape, as stated
• Oil dipstick tube gasket is tight. When engine is running, if I pull the dipstick, I feel some air blowing but nothing violent. I have read of bad piston rings causing oil to spray out the dipstick tube, or the pressure to cause the dipstick to shoot out. Neither of those things are happening to me...
• The gaskets on the engine, though leaking oil, are all in good shape. Screws are all tight, engine faces were clean prior to installing gaskets

 

What I'd like to do next is a Leakdown test - I am hoping my Autozone has one I can rent but if not I would buy one, along with a compressor. But I have so many questions

• Does anyone know of a written up guide with photos or a video showing how to do a leakdown test on a Kohler K series specifically? Found ones online for general engines but I know these have the automatic comprpession release so I'm not sure how to navigate that
• Do the leakdown kits come with the adapter for our spark plug hole threads? Or is that something separate I need to source?
• I'm also a bit confused on how the leakdown test works. When engine piston is top dead center, are both valves closed? If not, how do I plug the exhaust and air intake?

 

I'm also trying to check anything else I can without/before doing the Leakdown test.

• Is there any simple way to check the head gasket? If I pull the head, I'm assuming I should replace the head gasket? Could a leaky head gasket cause the increase in pressure? 
• If I do end up pulling the head, anything I should do in there or take photos of prior to putting it all back together? 

 

Thanks all for your advice here.

 

[squonk 41,778]

The "Blowby will not cause oil to blow out gaskets"  is 

 

I've worked on engines for 50 yrs. Excessive blow by will blow out anywhere it can unless there is a large enough hole to relieve pressure in one spot. You are just spinning your wheels. I know you want a miracle answer so you don't have to take the engine apart , but either find another engine,  rip into it or by oil and speedi dry and some rags. 

 

Leakdown testers come with the adapters. You test at top dead center with the valves closed

Edited January 7 by squonk

[Alrashid2 355]

Fair enough @squonk. Can't deny I am hoping for something better. But I also know blowby can be caused by other things and I'm having a hard time figuring out a good way to confirm its not those things... If a simple breather issue can cause these symptoms, why not another part of the engine? Just trying to hit in order of cost and effort before jumping to an engine rebuild or even replacement...

 

I'll see about doing the leak down test. Maybe I'll buy a cheap compressor from harbor freight...

 

I did find a cheap leak down tester on Amazon. It only shows pressure on one side though, and percentage on the other - would this work?

 

https://a.co/d/iqRZgi3

[Achto 28,083]

1 hour ago, Alrashid2 said:

It only shows pressure on one side though, and percentage on the other - would this work

 

This is how a leak down tester does work. The pressure gauge shows how much air pressure you are pumping into the cylinder. The instructions will have a recommended pressure to set the regulator to. The percentage gauge shows you the amount of air loss that you have. Any percentage in the green is good, yellow = marginal, red = you got problems.

 

Remove you air filter, crank case breather cover, and muffler as well if it comes off easy. Lock you flywheel so that your piston stays at TDC.

While tester is hooked up you will listen in 3 spots for air leakage. 

Hear air through the carburetor = You have a leaky intake valve

Hear air through the exhaust = you have a leaky exhaust valve.

Hear air through the crank breather = you have bad/leaky piston rings. ( If this is where your air is leaking, then the bang is blowing past the rings and into the crank case when the engine fires. ) Note: you will always have a bit of leakage to the crank case, if the percent gauge is in the green it is acceptable. 

 

A leak down tester is merely a tool to tell you how much compression and bang power you are loosing and where it is going. 

 

 

 

Edited January 8 by Achto

[squonk 41,778]

One of your other posts said it leaks bad under load. That's when the combustion pressure is the highest. That points to the most likely cause. Blowby. A blown head gasket will not cause blowby. A leaky intake valve will blow through the carb. A leaky exhaust valve will pop out of the muffler. If the gaskets are in good shape as you say and the breather is installed correctly it is blow by from the rings forcing the oil out.

[Alrashid2 355]

UPDATE!

Sorry guys, I have been sick with the flu all week so didn't get a chance to get back to you guys or even do much to the tractor.

 

Finally got sick and tired of being sick and tired and pushed myself to get back in the garage. I know blowby can't be fixed without an engine rebuild, but in the past I have been able to reduce it by using thicker oil. Likewise, I have seen cases with other small engines where the piston rings get suck and allow some blowby, and can sometimes be loosened back up. So, I did a few things:

 

1. I pulled the spark plug and using a plastic pipette, placed about half an ounce of Marvel Myster Oil on top of the cylinder. I let that soak overnight before starting the tractor. For the hell of it, I also poured 2 oz of MMO into my 2 gal fuel tank and ran that through after too (made the exhaust smell sweet!)
2. I drained my oil (10w30 basic Walmart brand oil) and replaced it with Rotella T4 15w40 diesel oil. I had read good things about the Rotella T4 with helping with blowby and burning oil, and likewise I think the 40w will help a bit with blowby at running temps.
3. While changing the oil, I drained the old oil into precise measuring cups and measured that, after all the oil I lost during my last plowing session, I still drained out 72 oz which is 2.25 quarts... that tells me I was definitely overfilled before. This time around, I filled with just 1.75 quarts of the Rotella T4 15w40 oil. This put me about halfway between the Add and Full marks.
4. Just to be safe, I pulled the carb and took apart the breather assembly. Everything was put together correctly, except that I noticed that one of the two gaskets was ripped. I doubt this would have caused my issues but I replaced the gasket with a new one. 

Well, today we got the most snow we've gotten since I bought my Wheel Horse - 4 inches! I plowed the driveway as I have and it performed beautifully. Once I was done, about an hour later, I parked her and popped the hood - NO OIL LEAKAGE! The engine face looked a bit wet but I believe that was just from snow hitting the engine and melting - wiping my finger it just felt damp, not oily. 

 

As far as I can tell, I had zero blowby or oil leakage during this session of plowing, with the engine under heavy load plowing uphill. I'm hoping that my "blowby" was really due to thin oil and being overfilled... but time will tell. I'm happy though! 

Edited January 19 by Alrashid2

[squonk 41,778]

Over filling will cause the oil to get whipped into a foamy, frothy mess and can easily overwhelm the crankcase breather system.

[oliver2-44 10,019]

44 minutes ago, squonk said:

Over filling will cause the oil to get whipped into a foamy, frothy mess and can easily overwhelm the crankcase breather system.

[lynnmor 7,447]

On January 8 I tried to tell you that the oil pan is special and the capacity would be 1 to 1.75 quarts.

[Alrashid2 355]

1 minute ago, lynnmor said:

On January 8 I tried to tell you that the oil pan is special and the capacity would be 1 to 1.75 quarts.

Thanks @lynnmor - my engine does have the A label but it looks like it was repurposed with the larger oil pan for Wheel Horses. Regardless the 1.75 it seems to be working well so far