Trying to help a friend of mine solve an engine
flooding problem (water in the crankcase). This is what we have looked at to date:
1. There is an anti-siphon loop in place - top of loop is 34" above waterline. Checked the siphon and it works properly.
loop is at the same height, 34" above waterline, exhaust
thruhull is above waterline.
3. The heat exchanger
/ exhaust manifold are both slightly lower (~3-4") than waterline.
is 60" below top of the exhaust loop (i.e. ~26" below the exhaust manifold).
level is ok - we know for sure its salt water
in the crankcase.
is 20+ years old - this is something that has happened only within the last couple of years. He was unable to figure out why water
was coming in so he has installed a gate valve on the exhaust (~16" below waterline). He has to close the gate valve and raw water
after shutting the engine down to prevent water
coming in). This last time, they had an issue and forgot to close the valves which stayed open overnight - flooded the next morning.
The only thing I can think is the exhaust pipe is filling with water (or has a certain amount of water in it when the engine is shut down) and creating a pressure head
in the exhaust manifold - this pressure head
could potentially be up to ~38" (distance from manifold to top of the exhaust loop). So is the water leaking in through the exhaust valves? A diesel mechanic
is suggesting he have new exhaust manifold (outlet) manufactured that includes a vertical loop going up before coming back down, connecting the siphon loop and then down to the muffler
. Not sure if this will solve the problem?
If its not coming in from the exhaust then is is possible to come in from inside the heat exchanger
- just wondering know if we should try pressure testing that? If there was a leak there this would be a continual problem - his issue only happens with engine off.