Coolant expansion tank always thirsty

[schatzi1]

Here is my current situation, then one or two questions.

I have a 2009 Hunter 33, purchased new 5 years plus ago now. Over the years, the engine overheated twice (Alarm came on), both cases due to seaweed stuck under the boat in engine water intake.

On both occasions, I stopped the engine right away and got the problem resolved before continuing the journey.

This summer, in a routine servicing, it was noted that the engine needed coolant and that the overflow tank was empty.

Since then, I have filled up both, the engine thru the radiator cap and the overflow tank several times, to the top limit.

I initially thought that it needed a bit more a few times due to air pockets etc.....

A few weeks ago, I again filled both engine and recovery tank to proper levels. I have ran the engine 30 mins or so at a time three or four times at the dock and all seemed good, the level in recovery tank remained same (Top Level).

Today for the first time, I took the boat out on the water and ran the engine for an hour at 3000rpm. I then returned at the dock with no visible or audible issues. (No alarm etc....)

Since the engine was hot, I did not open the cap to check it. What I did is look at the recovery tank and to my surprise, it was completely empty again. Note that the tank was noticed empty a few minutes after the engine was off.
Assuming that the overflow tank is to fill up as the engine gets hotter, I am sure it is still empty as I type this, hours after the engine has run.

Other info:

I looked under the engine, in the bilge etc and see no visible leaks or coolant.
I do not smell coolant odors when boat is running.
I see not visible leaks or coolant in the water near the dock when ran the engine for 30 mins or so.

Question:

Should I add more coolants in the recovery tank, again at the max level?
Over the last few months, it has been approx. 2.5 or 3 litres added total.

Is it common to have to fill up that ever thirsty tank so often? (I assume not)
Any common causes for this?

Thanks in advance for reading my long post.

 

[woodster]

what kind of engine is it ...

regards

woody

my guess is it is leaking coolant from the freshwater side to the sea water side of the heat exchanger ....may be a good time to service the heat exchanger and you may find your problem there ....

 

[Dan Hill]

This is not normal. Coolant is not a consumable product. I would suspect your heat exchanger is leaking coolant into your sea water system. When fully hot your coolant it's under pressure and the sea water side is not. Possible test would be to somehow test the exhaust cooling water for glycol. Not sure if the concentration would be sufficient. Another test would be to pressure test the coolant while monitoring the sea water at the exhaust injection point.

Good luck on your search.

PS: woody beat me to the punch, but I'll leave my post as reinforcement.

 

[schatzi1]

Sorry, should of specific, I have a Yanmar 3y30

 

[woodster]

This is not normal. Coolant is not a consumable product. I would suspect your heat exchanger is leaking coolant into your sea water system. When fully hot your coolant it's under pressure and the sea water side is not. Possible test would be to somehow test the exhaust cooling water for glycol. Not sure if the concentration would be sufficient. Another test would be to pressure test the coolant while monitoring the sea water at the exhaust injection point.

Good luck on your search.

PS: woody beat me to the punch, but I'll leave my post as reinforcement.

wow thats a first for me lol i was glad to see to minds thinking a like

regards

woody

 

[schatzi1]

wow thats a first for me lol i was glad to see to minds thinking a like

regards

woody

Thanks guys for the quick replies.... sounds like this is a common cause. If the leak is from the heat exchanger, is it normally a huge repair? a warranty items etc....

 

[Bill Roosa]

Purchas a pressure tester. Fits on the "radiator cap" on the engine and pump it up. If she holds pressure then your fine. I'm betting you have a leak though
the expansion tank will show loss of coolant right after you turn off the motor due to the "at temp" coolant starting to cool down. It sucks the coolant from the expansion tank but should only suck it down to the "full cold" line.
I agree with woodster, coolant is leaking into the raw water cooling system and getting pumped overboard. Given the large quantity of raw water going through the system and the small amount of coolant you would not notice it in the exhaust

 

[woodster]

Thanks guys for the quick replies.... sounds like this is a common cause. If the leak is from the heat exchanger, is it normally a huge repair? a warranty items etc....

if you don't have any metal parts that are damaged and you probably don't it no big deal just some work and a few gaskets and you should be good ...if you feel you are not capable of doing this find a buddy that has been there and get him to help you and teach you how to do it and then treat him or her to something nice to say thank you .......its probably not under warranty at this time as the sea weed is/was the problem ....

regards

woody

 

[seadaddler]

Coolant

My 3ym30 is 2007 and always seem to need me to add coolant and i checked all but never found any leaks and my expanion tank is always empty and no problems

 

[Ralph Johnstone]

My 3ym30 is 2007 and always seem to need me to add coolant and i checked all but never found any leaks and my expanion tank is always empty and no problems

I had the same problem right out of the starting gate on a 2GM20F and couldn't figure it out for love nor money. The heat exchanger was always full to the top but the exp. tank was always near empty. Fill it to COLD FULL and run it and it would be down again. And there was always a pool of antifreeze under the engine, but from where ?

Finally traced it down to the fact that the exp. tank is mounted on the engine (shown below) and gets shaken at low RPM to the point where coolant comes out from under the lid of the exp. tank.

Finally decided to remove the hose from the exp tank and feed it to a small jar to see what came out of the heat exchanger after being under full load for a few hours. Not a drop. And don't ask ........ this is pure occult as far as I'm concerned .

If you want to go at it theoretically, the coolant only gets to 175 F under full load so there's no vapour pressure there. Maybe the hoses on the engine and hoses to/from the hot water tank allow enough volumetric expansion that no pressure is generated to lift the cap and blow into the exp. tank.

To this date, the .exp. tank is left bone dry and the heat exchanger never loses a drop :cry:

 

[richk]

Schatzi1
Had a similar problem a couple of years ago. Hose from engine to hot water heater passed through a stringer and a hole was worn in it. Coolant leaked into liner; no coolant visible.
Rich

 

[Claude L.-Auger]

Before you start tearing things apart, do as Bill suggests: get a pressure tester and pump it up. Borrow, buy or rent it. Pressure should go up to about 15 PSI. And stay there ! If pressure drops, you have a leak somewhere. I would start with the easy stuff, i.e. by-pass the water heater heat exchanger and check pressure again. If no leak then it's either the hoses or the exchanger in the tank itself. If you still have a drop of pressure then your leak has a good chance of being in the heat exchanger of the engine. If the leak would let the antifreeze get in the engine through a faulty gasket, you would get some smoke and a sweet smell. Good luck

 

[bryan crites]

coolant leak

i used red die in the mix. found it in three tries.

 

[rardiH36]

Owning a boat with a much older engine, I might be barking up a wrong tree here about yours.

If you do determine that you are loosing the coolant through a breach in the heat exchanger tubes, seems to me that five years new is too soon for this to normally occur.

Do you have a zinc mounted on your heat exchanger? Has it been checked/changed a few times over the years?

The zinc on my heat exchanger seems to get fully sacrificed over a period of six months or so .... independent of how frequently I use the engine. And for my heat exchanger zinc, which is externally mounted from the engine and is electrically isolated from any other metal (since it connects to sea and coolant only through the rubber hoses), I've always been mystified why the zinc sacrifices. I would have thought that with the exchanger connected like this, it's metal would behave much like bronze thru-hulls ... not bonded to anything, so not really effected (normally) by electrolysis. Perhaps the tubes and the heat exchanger body alloys have different levels of copper and iron which sets up differences in electrical potential?