Crankcase pressure test

[anesthes]

Doing a pressure test on a 717 that I just had to rebuild the top end on because of a piston failure.

I think the failure was due to lubrication since it only affected one cylinder, however I wanted to do a pressure test to see if the outer crank seals were leaking.

So I made some block off plates and I pressure tested the intake and verified that Eric escaped out the pulse hose.

From what I understand it should hold 5 PSI for 3 minutes. I found that it does leak about a half of PSI in that time but it'll hold at least two to three psi for 20 minutes or so.

I also pumped it up to 10 PSI, In the first three minutes it loses a few psi but it still takes 20 to 30 minutes to completely leak down.

Obviously that is a minor leak, but is it big enough to worry about? I mean I imagine that's not really enough volume of air to cause a lien condition?

as far as the lubrication issue, I'm not really sure what happened I'm thinking when I disconnected the lines I failed to bleed the pump. Both squirters have oil in their lines. I guess I'll use a tank of premix and water test it.

 

[Whus02]

It is important to note that air leaks never get smaller on their own. While you have the engine out, you might as well find the leak and fix it before it gets big enough to cause a problem. Also, air leaks are generally worse when the engine is at operating temperature.

 

[anesthes]

It is important to note that air leaks never get smaller on their own. While you have the engine out, you might as well find the leak and fix it before it gets big enough to cause a problem. Also, air leaks are generally worse when the engine is at operating temperature.

The engine is not out, it's currently in the boat. I just did a top end in place. If I have to take the engine out again I will probably just get a new engine.

 

[Whus02]

In that case, it's up to you to decide. You can run it, but make sure to check your plugs pretty often to make sure you aren't running lean.

 

[Lake Sailor]

Based on some experience I have had with a rebuilt 717 in my GTI, I'd not worry too much about it. Keep an eye on the plugs as Whus02 says.

You could make it worse

Edit: I assume you can't identify some easily fixed leak

 

[mikidymac]

Proper leak down is 8 psi for 10 minutes and it should not move at all if it does you need some soapy water and find the bubbles.

 

[anesthes]

Proper leak down is 8 psi for 10 minutes and it should not move at all if it does you need some soapy water and find the bubbles.

That would be easy to do if the engine was on the bench and the mag and PTO was removed, but at the boat it's impossible.