Fresh water-closed system over run by salt water, leaking into bilge

[whitesharkseeker]

So I have a 1996 5.7Gi VP, fresh water cooled with heat exchanger and now the fresh water reservoir is overflowing, dumping salt water into my bilge at higher RPM's. How is this possible? Leak in HE? The boat ran fine as long as I had bilge evacuating all the salt water spilling out onto engine and into bilge. Finally engine overheated and limped back to harbor. I heard a sucking sound from HE when I made it back to the dock and after engine shut down. Engine only has 4,000 hours on it. I have done some research on the net but get confused with all the problems that it can be, from blockages to head gasket. Engine ran fine before this catastrophic event. Any other thoughts? Thank you.

 

[alldodge]

For me 4K hours is a bunch, but my guess is you blew a head gasket. In any case, check your oil level to see if its come up, if it has then there is water in the block

 

[Scott Danforth]

first and foremost

pressure test the cooling system

you will most likely have to pull the HX and have it tested. usually the solder joints at the tube sheets fail long before 4k hours

if that passes, then pressure test the cooling jacket on the engine.

 

[whitesharkseeker]

Thank you for the advice. I was flushing engine tonight and during warm up water is pouring out of the reservoir tank into my bilge. I also notices a few bubbles in the oil on dipstick (water?) but maybe that was water from the hose after rinsing salt off starboard engine that infiltrated down dipstick tube. Anyway, trying to understand how a blown head gasket (if that's the case) can back up my cooling system. Also wondering the mechanics how a restriction in the downstream side of the heat exchanger can make saltwater infiltrate my closed water system?

 

[alldodge]

If you HX has a crack in it, then salt water is mixed with antifreeze.

If head gasket is blown, then combustion pressure is released into the antifreeze side of the HX and pressure becomes excessive enough so it starts blowing out the cap

 

[whitesharkseeker]

Thank you I will investigate further. Keep in mind that salt water is dumping....and I mean dumping....out the reservoir cap. This confuses me and don't know how combustion pressure can pull salt water in a closed cooling system. Fixing sounds expensive if it's a blown head gasket (milky oil) so just wondering if I should re-power with 4,000 hours.

 

[Lou C]

If salt water is dumping out the reservoir cap, then for one your heat exchanger must be leaking from the raw water side into the antifreeze side. However, for the exchanger to get that pressurized, something else has to cause it and that could be combustion gas getting into the coolant. 2 separate problems. Check motor oil, do you have either water or antifreeze in the oil? Do you have water or antifreeze in the cyls? If you want to save that engine got to find out fast....

your overheat was the clue to all of this...overheated engine...could be blown Head Gaskets...cracked heads...I had both...a few years back...and wound up replacing the heads with re-man ones...you might be able to do the same...if you get the any water or AF out of the engine fast....

 

[Scott Danforth]

Thank you I will investigate further. Keep in mind that salt water is dumping....and I mean dumping....out the reservoir cap. This confuses me and don't know how combustion pressure can pull salt water in a closed cooling system. Fixing sounds expensive if it's a blown head gasket (milky oil) so just wondering if I should re-power with 4,000 hours.

stop STOP STOP using your boat.

read post #3

pressure test your HX and your block

find your problem

fix your problem

then go back to boating

 

[whitesharkseeker]

Yes, great advice and have stopped using the boat. Thank you guys very much for the help. I can't tell if anti-freeze was in oil but the dipstick shows brownish demarcation on the oil line suggesting water. I know all my fresh water coolant was long discharged and replaced by salt water. Sounds like two different problems, perhaps related.

 

[whitesharkseeker]

So I just pulled my heat exchanger to pressure test. Before doing that I unscrewed block water plug and, surprisingly, just a few drops of water came out. I did an engine compression test and all was ok so wondering if it is possible to still have a blown head gasket with a normal compression test. Will pressure test block next. Thanks.

 

[Scott Danforth]

if you pulled the block drain and only a few drops came out, you have other issues

at a minimum you should have had about 2 quarts of coolant or sea water come out each side of the typical small block cooling jacket

 

[Lou C]

 

[whitesharkseeker]

Thank you for the great info. I took HX out just need to figure out where I can buy a pressure tester. I suppose you would hook it up at the reservoir and block the fresh water hoses? Do the spark plugs need to be installed since i pulled them out already. Thanks again, Eric

 

[whitesharkseeker]

Great pictures by the way. I take it all that rust is the water intrusion areas.

 

[alldodge]

The HX has one raw water in and one out. Block off either then make something to close off the other end and be able to connect a pressure gauge and a bicycle pump. Pump it up to 15 psi and see if it holds, just air no water

 

[Bt Doctur]

Remove the HX for testing because you will find it bad
If its that bad just use your hose water pressure, put hose on raw water inlet side and cap the raw water outlet side You will see it come out the fresh water side if you have a leak

 

[Lou C]

Great pictures by the way. I take it all that rust is the water intrusion areas.

What looks like rust is actually the old intake gaskets, they were baked on like Krytonite! Took forever to get off.....of the intake....the heads....I replaced…..