Crusader engine missing coolant. Ideas?

[MV Wanderlust]

Friend of mine has twin crusaders. One is operating normally. During a multi day cruise, the other engine ran fine for the first three days then overheated at the start of the fourth day. He immediately shut it off and checked it over. He discovered the coolant reservoir was empty so he refilled it. And refilled it. And refilled it. After it took a lot of coolant, it was fine the entire day. The next day, the same thing happened. There are no obvious signs of leakage in the bilge so we’re theorizing the leak is in an exchanger and the coolant is being ejected with the exhaust. We thought about throwing some dye in the coolant to see if it shows up in the discharge. Any other ideas or diagnostic approaches?

John

[boatpoker]

Originally Posted by JohnEasley

Friend of mine has twin crusaders. One is operating normally. During a multi day cruise, the other engine ran fine for the first three days then overheated at the start of the fourth day. He immediately shut it off and checked it over. He discovered the coolant reservoir was empty so he refilled it. And refilled it. And refilled it. After it took a lot of coolant, it was fine the entire day. The next day, the same thing happened. There are no obvious signs of leakage in the bilge so we’re theorizing the leak is in an exchanger and the coolant is being ejected with the exhaust. We thought about throwing some dye in the coolant to see if it shows up in the discharge. Any other ideas or diagnostic approaches?

John

Check the oil, betcha it's the colour of a chocolate milk shake and the motor is toast.

[Lepke]

If no leaks are apparent coolant can escape from cracks in the head or cylinder, blown head gasket, and the heat exchanger. If the engine had good compression, it's probably the exchanger. Any radiator shop should be able to pressure test it. You can test it if you make up some adapters, have a gauge and a bicycle pump.
Dye might work, but it's not a good idea to put things in the coolant not designed to be there. It could effect heat transfer, water pump bearings, etc.

[MV Wanderlust]

So basically, it's a simple, closed system and the coolant should pretty much remain within normal expansion and contraction levels. If it's low, it went somewhere and there are limited routes out of the system.

• There could be a leaking hose or broken hose clamp. That would be the first place to check and the best case scenario.

• There could be a crack in one of the internal heat exchanger tubes, which could be allowing the coolant to be discharged in the exhaust. Not a horrible repair.

• There could be a bad head gasket or cracked head, which could allow it to leak externally. That should be visible.

• There could be a bad head gasket or cracked head that allows the coolant to leak into a cylinder and get mixed into the combustion chamber. That should present itself as steam in the exhaust, shouldn't it?

• There could be a crack in the block that allows the coolant to leak into the lower engine. That would manifest itself as chocolate milk-looking oil and would be the worst case scenario.

To diagnose:

• Check the oil to see if it's chocolately. If not...

• Top up the coolant and run it. Check for obvious external leaks on hoses and around the heads.

• Run a compression test. If the oil is okay and the compression test is good...

• Pull the heat exchanger and take it to a radiator shop for inspection/repair.

Did I miss anything?

[AfterHoursNLCT]

Pull the end caps from the heat exchanger and pressurize the fresh water side. You'll see the green antifreeze if the heat exchanger is indeed leaking...

[MV Wanderlust]

Originally Posted by AfterHoursNLCT

Pull the end caps from the heat exchanger and pressurize the fresh water side. You'll see the green antifreeze if the heat exchanger is indeed leaking...

Another good suggestion. Thanks, AH. Looks like you're on a Silverton 34. By coincidence, my buddies boat is a Silverton 36 Convertible.