Coolant System Integrity

[Jocko_51_B3B]

I applied 5 psi air pressure to the coolant system of my 218 and the pressure leaked down to zero after 40 minutes. So OK, I know there's a leak somewhere, but what is considered an acceptable leak down rate? Zero? Is there a rule of thumb about this?

 

Meanwhile I'll keep looking, listening, and spraying soapy water on bolt heads etc. If I still can't find a leak, I'll fill it with water and check for leaks that way. Thanks.

 

Edited May 26, 2019 by Jocko_51_B3B

[Don Coatney]

Is your radiator vented on the top as pictured below?

 

[Jocko_51_B3B]

I found the leak. The engine has been re-sleeved and there is a leak coming from near the bottom of the #4 cylinder sleeve. So for now I'll disassemble the engine and take it back to the rebuilder. I should have pressure checked the block immediately after the rebuild. Live and learn. Hopefully the block can be repaired. If not, then the search for a replacement block begins.