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Old 07-21-2013, 12:19 AM
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SWGA Boater SWGA Boater is offline
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Join Date: Oct 2012
Boat: Not a MasterCraft
Location: Southwest Georgia
Posts: 203
Originally Posted by [email protected] View Post
Yes a normal motor will show 10-15% leakage, your numbers are mostly good, cylinder 8 is iffy at best, I would start looking at #8, anything above 15% and you need to start thinking about investigating and possible rebuild. I recently did a leak down test on a 5.6L titan with 135,000 miles none were over 8%. I would clean top end, pistons etc. Mix up some atf/ water mix 50/50, (marvel mystery oil can also be used)remove all spark plugs insert several teaspoons full of mix into each plug, let soak for 10-20 minutes while slowly rotating engine over by hand every few minutes, then spin engine over with starter motor, plugs still out to remove excessive atf mix, install plugs, it will smoke like a chimney until all atf is burned off, run it for a while, let cool down and recheck leak down.
Thanks for the suggestion. I talked with a mechanic yesterday and he suggested the same thing, except pouring down carb throat until engine dies and then letting it sit over night. Last resort before going into engine i guess.

Any idea what is the difference betweeen the oil the engine uses and atf for the rings? Why would atf be a better choice?
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