PT425 and Robin/Subaru Engine Oil blow-by

[woodlandfarms]

stupid question but has your property changed? are you tilting the engine more than you have in the past? And your PT, it is a verticle engine, correct?

 

[atwood]

My property is still the same, hilly West Virginia. Other than sometimes going up and down vertically some steep hills I typically keep the 425 on gentle slopes. I should note that this blow by in the air filter has been going on for sometime now , perhaps several years. I had mentioned it to the mechanic/friend I know over that period but since it was running okay he didn't have any concern or idea why it was happening and I just kept running it, adding engine oil here and there not really paying a lot of attention. However this past summer when outside temps were higher cutting grass, brush cutting, etc, the oil residue was burning off the outside of the engine. That could of been the hose on the oil cooler that had worked loose but either way after more inspection I decided that I should pay some long overdue attention to the problem or find out the cause.

 

[woodlandfarms]

Well, a steep slope can cause oil to get into the carb. You say this has been going since the beginning. I am not saying it isn't your engine, but I am wondering if you are pushing the machine further over the edge as you have become more comfortable. That, and maybe your oil level is too high to begin with.

The thing that is odd is that your compression is still solid. A leakdown test would be a good double check but.

 

[MossRoad]

Whats the difference between a compression test and leakdown test and how are they performed?

 

[ponytug]

I'm sure you have thought of it, but if the oil level is even a little too high, there will be splashing and foaming, which will raise the oil level higher, resulting in more foaming and higher oil levels... The end result will be lots of oil spray out your breather tube. It is also hard on your crankshaft and connecting rods to be slapping oil.

Foamy oil isn't a great lubricant, either. Think of it as oil with 20% of the good stuff and 80% bad stuff (air).

Just a thought.

All the best,

Peter

 

[woodlandfarms]

As I am no mechanic, I was told a compression test was a quick turnover of the engine and guaging what the pressure was.

Leakdown was to get the piston into TDC or as close as possible and wait for X time to see how much pressure escapes.

But heck, what do I know. It always sounded basically the same to me.

Knew I would find it.

Compression-leakdown test

 

[MossRoad]

Thanks for the link!

 

[atwood]

Thanks everyone. yes, from what I've been told the leak down test is more involved than the compression test like Woodlandfarms indicated. And maybe the steeper slopes have something to do with the blow by, it surely is possible. I did take the 425 back to the mechanic and this time, not only the blow by (very little) but more oil was over the bottom of the tub on the oil cooler side. He put some dye in the oil and seems at this point more is coming from the oil cooler area. He is going to pull the engine and run it on the bench to get a better look. Wherever its coming from the flywheel seems to blow a bunch around. Other than that the engine runs probably better than it ever has or at least for a long time. Will let you know what he finds.

 

[arrow]

Whats the difference between a compression test and leakdown test and how are they performed?

Basically Moss, compression reads just pressure on it's gauge and just begins to tell the story. Sort of reading the book flap to get the gist of the book. A leak down reads percent of leakage. Leak down is more for chasing down where the leak is as air is fed into the gauge adapter and seeing where it exits. If air is coming out the PCV valve for instance, you have a bad piston ring. Coming out of other areas describes if you have a cylinder head or valve leak etc.. Both gauges are inserted into the empty spark plug hole. The only thing that the compression gauge reads is what is being created by the piston. The leak down gauge is fed air or sometimes nitrogen. It is zeroed and then air is blown in which is then dispersed within the engine cylinder to measure first a leakage percentage and then where the leak is as the air attempts to find the least resistive path for exiting.

 

[Frank Sorbello]

I too was having problems with gas in my oil. I put a shut off valve on the fuel line before the fuel pump. Whenever i am done with my PT-422 for the day I shut the valve off. My oil has been good ever since I started using the shutoff valve.