Leakdown Test Results

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I have a two cylinder Kawasaki KD590V in my lawnmower. Last fall, I had a failed headgasket which I replaced. This spring, I've been questioning whether the repair was successful so I thought I'd try a leakdown test and see what happened. The reason I'm questioning the repair is that I can get a bit of antifreeze coming out of the overflow bottle when I'm driving around and it's sloshing in the bottle. But I don't see any bubbles out of the overflow tube, nor do I see any bubbles when I run the engine with the radiator cap off. So I figured a leakdown test might tell me something.

I'm getting 20-22% leakage on both cylinders. No air hissing from carb or exhaust. No air bubbles coming up out of the radiator. The oil in the fill tube moves, and moves more and more the higher I turn the pressure up. So, we have leakage around the rings. I don't hear any sharp hissing, but hear a sound around/behind the head. It's more of a "filling up a tire" sound, not a hissing. I've never done one of these before, but was expecting hissing/bubbling somewhere with this amount of leakage.

So...Question #1. Given the lack of any bubbling action in the radiator when doing the leakdown. Can I be reasonably confident my head gaskets are intact?

Finally, from what I read 20% leakdown is getting into the grey zone in auto engines. I'm assuming the same is true for small engines?
 
20% leakdown sounds pretty good to me.
You would really have to have a seriously failed head gasket for it to leak at the 100 psi supply pressure of a normal leakdown test. In operation, peak firing pressures of gasoline engines can be 1000 psi, depending on the compression ratio.
 
Originally Posted By: Chris142
Have you replaced the radiator cap?


Replaced this weekend, along with the overflow tube. I haven't taken it out on rough ground since to get the antifreeze sloshing around to see if it's still dripping out the top.
 
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