Other than checking the cylinder compression (on another thread) I am also testing the cooling system for a possible leak. I got a loaner Stant style pressure tester from Autozone and then checked online for directions on how to use. (http://ww2.stant.com/repository/documents/JB-1164_20091.pdf) When I tested the 7# psi caps, the caps from both 8.1L engines would prevent any higher pressure than about 7# but neither one would hold any amount of pressure. The online tester directions indicate that the caps should hold pressure which makes sense to me. I purchased an automotive radiator cap and it would hold pressure while preventing pressure above 7#. Are marine heat exchanger caps different that automotive (other than cost which is normal for anything to do with boats)?
Another test is to connect the tester and start the engine and observe the pressure. One engine does show pressure slowly building up to about 7-8 lbs but the suspect engine does not. However if a pump the tester up to about 8-10 lbs it will hold pressure both with the engine running or with it shut down. So it "appears" to be holding pressure OK and I don't know now if the recent loss in coolant may just have been due to an air pocket in the system which finally cleared.
Ideas and suggestions please.
Erich
Another test is to connect the tester and start the engine and observe the pressure. One engine does show pressure slowly building up to about 7-8 lbs but the suspect engine does not. However if a pump the tester up to about 8-10 lbs it will hold pressure both with the engine running or with it shut down. So it "appears" to be holding pressure OK and I don't know now if the recent loss in coolant may just have been due to an air pocket in the system which finally cleared.
Ideas and suggestions please.
Erich