Loosing Coolant

[RicM]

I carefully topped off my coolant reservoir when the engine was cool Friday. Went fishing Saturday AM and ran for 5 hours at a variety of speeds including 10-15 min at 3500RPM. Sunday AM, completely cool engine, and the reservoir is down about an inch, 4-6 ounces. Where could it be going?

[jleonard]

Do you have a recovery bottle?

I forget what engine you have and how many hours and all that stuff that might be relevant.

[RicM]

Sorry, it's a 2003 28 TE with 530 hours on the Yanmar 315. I am waiting for parts to do the 500 hour service which calls for replacing the mixing elbow and some hoses. Yes there is an overflow bottle (that's what I was referring to as "the reservoir")

[Russell]

As I understand it the overflow tank fills because of thermal expansion when the engine is running and the coolant gets reabsorbed as the engine cools down. Isn't it possible that it was reabsorbed into the engine coolant system as it cooled down? If the overflow tank was low before you filled it the engine coolant may have had some space. The other less likely possibility is that you overfilled the reservoir and it overflowed into the bilge when the engine was running at normal temperature.

[RicM]

Because I filled at dead cold engine and checked with dead cold engine the next day the level should be the same. There is a 50% overflow capacity in the reservoir. It didn't used to use that much coolant in a season.

[chiefrcd]

Rick, I have basically the same engine and I have to top mine off a couple of times a year. I carry a gallon with me that I've had for 5 years so it's only a inch or so at a time.

[jleonard]

Because I filled at dead cold engine and checked with dead cold engine the next day the level should be the same

You could have had an air pocket that is now filled.

You could have a loose clamp and a leak that you haven't yet found.
I put all new hoses on mine a couple of weeks ago. Thought she was all buttoned up even after running at the dock for 30 minutes (only got to 120 deg F).
I was ready to call it quits when I noticed a very very small weep. One of the hoses needed a few more cranks on the screw.
Once she heats all the way I will touch every hose clamp again to make sure they are tight.

[RobS]

Ric,

I remember adding a few shot-glasses of coolant at the start of last season to the overflow bottle. I also replaced the coolant cap on the fresh water tank (the one on the engine - not the reservoir bottle) since the cap is the decision maker for the flow between the engine mounted fresh water tank and the bottle.

[RicM]

Rob,

Part # on the cap or will one from the auto store do?

[RobS]

The Yanmar part # is 129107-44590. I do not think you would find it after-market. It's a 2-way cap, I don't recall the pressure rating, 12 to 15 lb's ?

When you fill next time, start with a cold engine, remove the cap and start and idle the engine and slowly continue to fill the tank upto the bottom of the neck with it running until she will not take anymore. Then top of the bottle to the max/full mark.

Have you checked the engine oil for any signs of moisture?

Also, if the coolant is getting into the exhaust via a leak in the exhaust manifold you could actually smell the coolant in the exhaust.

Quite unlikely you have any problems.....