Oil in water after acid wash

[gravy26]

I gave the A4 an acid flush as prescribed by Don, my blend might have been a little higher percentage (40% muratic acid to 60% water) for 15 minutes.
I then ran the engine with fresh water for 10 minutes to flush the acid out.
I had to leave the boat for an hour to get antifreeze.
Once back the engine would not start, I checked the dipstick and found water in the oil.
What are the chances water that was in the bucket siphoned back into the engine vs acid burning a hole through the water passage vs the water pump leaking?

[ndutton]

I gave the A4 an acid flush as prescribed by Don, my blend might have been a little higher percentage (40% muratic acid to 60% water) for 15 minutes . . . . . . What are the chances water that was in the bucket siphoned back into the engine vs acid burning a hole through the water passage vs the water pump leaking?

Acid opening up a hole is a very real possibility, perhaps even likely in your case given the sequence of events you reported but know that if it did, the affected area was paper thin to start with so in a way you may have done yourself a favor by discovering this under controlled circumstances rather than out at sea. I suggest a cooling system pressure test is the next thing you should do.

[joe_db]

Yes - pressure test is in order.

[gravy26]

I was thinking the same thing. Divine intervention?
I’ll be pressure testing this week.

Thanks,
Mike M.

[JOHN COOKSON]

Agree a pressure test of the cooling system is in order.

If you left the end of a hose in bucket of water that was higher than the engine while you were gone to get antifreeze a siphon is a possibility. As a warm engine cools it can create enough of a vacuum to start siphon.

TRUE GRIT

[gravy26]

Back at the boat this weekend, water in oil not from siphoning or water pump. There was water on the two back spark plugs. What are the chances the acid ate through the head gasket or exhaust manifold gasket?
I noticed when running, when I plugged up the water intake hose the engines rpm increased and decreased when allowed to draw water again.

Mike

[edwardc]

Yes, you have a breech. The water puts out the fire, which is why it runs better with the water blocked off. Though possible, I think the gasket is unlikely to have been affected by the acid. More likely a thin spot in either the manifold or the head gave up the ghost under the acid bath.
You need to pressure test the whole system before disassembly to confirm the leak. Then pressure test the manifold (still without disassembly) to isolate the leak to it or the head & block.

[joe_db]

Yes, you have a breech. The water puts out the fire, which is why it runs better with the water blocked off. Though possible, I think the gasket is unlikely to have been affected by the acid. More likely a thin spot in either the manifold or the head gave up the ghost under the acid bath.
You need to pressure test the whole system before disassembly to confirm the leak. Then pressure test the manifold (still without disassembly) to isolate the leak to it or the head & block.

Manifold would be the best news, followed by the head. A hole in the block will be bad news

[gravy26]

After replacing the head gasket l still found water entering the engine. I pulled the engine out, pulled the head off and sent to a machine shop for cleaning, magnafluxing, and pressure testing. All came back good, no cracks or warps.
Before installing the head I filled the water jacket on the block from one of the small ports on top with water and found the culprit - see attached.

I can get to the hole from the exhaust port and somewhat from the water port on top. To get me back on the water this season I'm planning to clean out the area all around the hole top and underneath and JB-Weld Hi TEMP it.
I realize the entire water jacket area is probably compromised and should start looking for a replacement block. The engine was rebuilt 10 yrs ago including a new crank and has 400 hours on it so the parts are just 'broken in' so I should be able to reuse most parts.

Thoughts?
Mike M.

[edwardc]

JB Weld is a temp fix at best, but it could get you through the season.

Since you have access to both sides of the hole, be sure to form a "mushroom" cap of JB Weld on both sides. This will help lock the plug in place instead of solely depending on adhesion.

[thatch]

Mike, That is a very interesting breach. Depending on the size and access to it, I'd be tempted to drill and tap it and install an Allen set screw. Sealing it with JB should keep it in place.
Tom

[ndutton]

Are you sure that's the only breach?

[thatch]

One method while looking for "hidden" cracks or breeches is to fill the water passages with shaving cream and then blow compressed air into the intake and exhaust ports. If you see bubbles, you've got a breach.
Tom