Drowned engine

[Loki9]

After installing my freshly rebuilt A4 in Santosha, I somehow managed to drown it in cooling water. After much hassle, I have it cleaned up and running again, but I haven't exactly figured out went wrong.

Here's what happened:

I ran the engine for 20-30 minutes. It ran well, no problems. I shut it off and went to lunch. When I returned an hour later, I tried to start it again. When I hit the starter, I heard a "clunk" and it did not turn over. I pressed the starter again and this time it did turn over, but did not start. Further attempts to start it failed. I stopped trying after I removed the flame arrestor and found water in the carb. I then disconnected the exhaust pipe and found water in the manifold too.

This engine has a fresh water cooling kit installed. An electric pump circulates coolant through the engine and a heat exchanger, while the A4's water pump pumps raw water through the heat exchanger. The water that I found in the carb and manifold (and later in the crankcase too) was raw water, not coolant, so it had to have come in from the exhaust. My boat is on the hard, and to run the A4 I had the water pump drawing from a 5gal bucket filled with fresh water. The bucket sat in the cockpit, with a garden hose keeping it topped off.

My only idea is that after I shut down from the first run water from the bucket in the cockpit siphoned down through the water pump, through the heat exchanger and into the exhaust until it filled the water lift and backed up into the engine. Is this plausible? I would never have guessed that water could free flow through the water pump when it's not turning, but I can't think of any other place the water could come from.

[edwardc]

From a bucket sitting in the cockpit down to the pump intake, there's probably about 2 feet of "head" to build up pressure. That works out to almost 1 PSI. If you don't have a siphon break between the heat exchanger's raw water out and the water injection point, then starting a siphon is a real possibility.

It's hard to believe that water will get past that pump. but apparently it does!

[ndutton]

It tells me you probably have some pump cavity or impeller wear so there is a poor fit with the faceplate. The pump will function with a minor gap like around 0.003" but much more than that and it will be on the replacement list.

[Laker]

I think that you are barking up the right tree. ( I am sorry to say that I have experience in drowning an A4 on the hard.) It is imperative that you get the engine running again as soon as possible , lest the water in the cylinders combines with the varnish-y stuff which coats the valve stems making a valve sticking adhesive. ( I have experience with that too.)

Write it up to experience and revive your mill.

Best of luck , Laker

[Loki9]

I think that you are barking up the right tree. ( I am sorry to say that I have experience in drowning an A4 on the hard.) It is imperative that you get the engine running again as soon as possible , lest the water in the cylinders combines with the varnish-y stuff which coats the valve stems making a valve sticking adhesive. ( I have experience with that too.)

Write it up to experience and revive your mill.

Best of luck , Laker

Here's what I did to get it running again:

Removed the spark plugs, exhaust hot section, and carburetor.
Soaked water out of the manifold exhaust port using paper towels.
Removed the transmission cover to inspect for water in the oil pan (none seen).
Cranked the engine over to blow water out of the cylinders.
Drained carburetor bowl and wiped out the throat with paper towels.
Replaced exhaust, carburetor, and spark plugs.
Started engine and allowed to warm up to full operating temp.

After running, I checked the oil and found that it looked like chocolate milk. In hindsight, the visual inspection through the transmission cover wasn't helpful and I should have changed the oil out before running it. So now I changed out the chocolate milk and refilled with new oil. I'll likely have to repeat this at least once to get the last of the water out.

[Loki9]

It tells me you probably have some pump cavity or impeller wear so there is a poor fit with the faceplate. The pump will function with a minor gap like around 0.003" but much more than that and it will be on the replacement list.

I'd say it's likely there is wear. When I rebuilt the pump I put a new cam shoe in and I was surprised to find the new shoe was nearly twice as thick as the old one (the old one was worn that much). However the pump works well and doesn't drip, so I'm staying with it for now.

[Loki9]

From a bucket sitting in the cockpit down to the pump intake, there's probably about 2 feet of "head" to build up pressure. That works out to almost 1 PSI. If you don't have a siphon break between the heat exchanger's raw water out and the water injection point, then starting a siphon is a real possibility.

It's hard to believe that water will get past that pump. but apparently it does!

Yeah, such a freak thing, but I have no alternative explanation.

[msauntry]

Not the end of the world. Another oil change or two and the A4 will be back to normal.