Coolant Leak - Exchanger?

[dmdiehl64]

Hello,

Noticed a sizeable drop in the coolant tank and topped it off. Went out for a sail and upon coming back I noticed we lost some more. When starting up the engine saw a glassy film on the water which is highly likely the missing antifreeze. Conservative estimate is a leak rate of 0.04 gal/hr, 0.13 L/hr. No antifreeze in the bilge or engine compartment.

Only place this could be leaking by is the exchanger tube bundle, correct? Anyone have experience with this?

Thanks!

 

[Ralph Johnstone]

WHAT IS THE ENGINE ? ? ? ? ? ? ?

Try a pressure test before tearing into pulling the HE as you could be looking at a head gasket problem. Cap off the HE discharge with hose fittings. Lead a piece of vinyl hose or other hose into the HE inlet, raise the hose up as much as you can and watch for a drop in level over 24 hours.

 

[dmdiehl64]

It's a Yanmar 3GM30F. I like the simplified pressure test you're suggesting. The one recommended in the service manual requires removing the exchanger and testing it in a water bath.

Wouldn't a head gasket leak lead to antifreeze in the oil, or white-ish exhaust gas? I'm thinking the liquid film that exited through the exhaust at the last startup is an indicator of leakage into the sea water cooling loop.

 

[capta]

First thing I'd do is check the oil. If it isn't milky, then move on to tasting whether the water that has returned to the tank is salty. If it is, then it is most likely the HX. To verify, remove the heat exchanger and plug the nipples for either the salt or fresh side except where you are introducing water from a garden hose, if available, or your boat's pressure water, if not. If one side holds pressure you can try the other, but if you aren't finding any water around the HX, then that is probably a wasted step. If you do find a problem with the HX, take it to a radiator shop for a fair repair cost.
If none of that produces a leak, then pressurize the system slightly more than called for and do a manual inspection of anywhere it could leak. Check or change all hose clamps and hoses. Good luck.

 

[jssailem]

• starting up the engine saw a glassy film on the water which is highly likely the missing antifreeze.
• No antifreeze in the bilge or engine compartment.
• Only place this could be leaking by is the exchanger tube bundle, correct

Glassy film could be antifreeze or could be unburnt fuel.

No AF in the bilge or engine compartment is a good sign.

Is there a thin mist of AF on the engine or below the coolant water pump? Age of engine and coolant pump is unknown There is a seal in the pump that can weep. Inspect the pump for coolant stain.

Definitely inspect the oil.

Your in fresh water so no way for salt water intrusion.

How long has it been since you inspected the heat exchanger? The last a long time but not indefinitely.

 

[Ralph Johnstone]

I like the simplified pressure test you're suggesting.

As I always say, start simple and work your way up ⇧ ⇧ ⇧ until you get an answer. Not vice versa.

 

[dmdiehl64]

Is there a thin mist of AF on the engine or below the coolant water pump? Age of engine and coolant pump is unknown There is a seal in the pump that can weep. Inspect the pump for coolant stain.

How long has it been since you inspected the heat exchanger? The last a long time but not indefinitely.

Thanks. There was no film or evidence of antifreeze in the engine bay. Power plant has 5,600 hrs on it, 1998, and without maintenance records there's no surefire way to know of any repairs. I did have the exchanger head off last year pulling a water pump blade out but didn't do any thorough inspection.

I'll do an oil change in a few days and check for signs of coolant.

 

[kloudie1]

The fat o-rings that seal the tube bundle to the housing and end caps are a likely suspect.. It would be unusual for a tube to corrode through in fresh water and coolant service on the different sides.. Part # for those rings is 24311-000700.. Toad Marine lists them for $3.00each.