Yanmar 4JH2 loosing coolant

[westernman]

My Yanmar 4JH2 is loosing coolant. Not a lot but I have had to put in 3 litres or so of antifreeze during the season. No obvious leak anywhere.

What are the likely candidates to look for?

--

 

[VicS]

Not a lot but I have had to put in 3 litres or so of antifreeze during the season

That's a helluva lot in my book. It should not need any!

Absolutely sure its not leaking externally. Circulation pump?? overflow ???

Possibilities. Heat exchanger leak and being lost with the seawater. Gasket and leaking internally in the engine. Turbo charger

I reckon the heat exchanger is the first one to look at esp if the engine is running sweetly.

Cant find a workshop manual for a 4JH2 only a 4JH3

 

[westernman]

I know it should not need any coolant adding at all - it was drained completely at the start of the season. The first time or two it was topped up I could believe is due to air locks working themselves out. But there can't be any more after a few hours of running.

Apart from this problem the engine (11 years old and probably fairly heavily used) is running perfectly - it always starts immediately, and purrs away smoothly at all speeds/loads. It does not use any oil at all. At bit of black smoke when giving it a burst at full throttle but thats all.

I will get the manual out and try and trace through carefully the cold water circuit - just wondered if there was any collective wisdom - like Yanmars always leak coolant from ......

 

[ianat182]

Yanmar losing coolant......

Possible faulty pressure cap on heat exchanger,or not secured correctly? perforated seals to H/E? Pipe clips cutting through rubber piping?

 

[westernman]

Possible faulty pressure cap on heat exchanger,or not secured correctly? perforated seals to H/E? Pipe clips cutting through rubber piping?

Thanks - that gives me somewhere useful to start. The cap on the heat exchanger sounds like a good one - after all the engineer may well have fiddled with that when draining the coolant during the service at the start of the year.

 

[Manuel]

My Yanmar 4JH2 is loosing coolant. Not a lot but I have had to put in 3 litres or so of antifreeze during the season. No obvious leak anywhere.

What are the likely candidates to look for?

--

You don't say how old the engine is or give any history. Fresh water circulation pump, rubber hoses, or at the worst an internal leak around the head gasket. Steam in the exhaust is the classic clue for that. 3l is a huge loss and needs to be found. I have a similar engine and the plastic header tank (overflow) is mounted in a way that causes the water to splosh out of the seal at the top. A bit of cardboard stopped that. You might be lucky and find that your problem is as simple.

If a good torch doesn't show you where the leak is coming from wrap some masking tape round various parts and hoses and inspect after a few hours use. Otherwise it might pay you to get a mechanic in to have a look and get him to do some of those difficult jobs at the same time to save you the trouble. Engine mountings, stern gear, etc.

 

[Sailfree]

I know it should not need any coolant adding at all - it was drained completely at the start of the season. The first time or two it was topped up I could believe is due to air locks working themselves out. But there can't be any more after a few hours of running.

Apart from this problem the engine (11 years old and probably fairly heavily used) is running perfectly - it always starts immediately, and purrs away smoothly at all speeds/loads. It does not use any oil at all. At bit of black smoke when giving it a burst at full throttle but thats all.

I will get the manual out and try and trace through carefully the cold water circuit - just wondered if there was any collective wisdom - like Yanmars always leak coolant from ......

I assume from you question the leak is not detectable by antifreeze on panel beneath engine and you suspect its an internal loss?

 

[ianat182]

I should have asked previously.
What symptoms led to your discovery of the coolant loss.? Was the engine overheating,steam from the exhaust or just a service interval check? Do you have a water temperature gauge fitted,and working? Could it be back pressure within the H/E tubes, so that the coolant is not able to travel,and vents out of the cap.

I lost my H/E coolant by overheating ,after the impeller became blocked in the raw water system ;very noticeable too, out of the overflow pipe and into the bilge. Shut down quickly and sailed back to a pontoon,and replaced the impeller,cleared all blockages, refilled the coolant, and back to normal after 1 1/2 hrs. I was lucky it did no damage.

ianat182

 

[westernman]

I should have asked previously.
What symptoms led to your discovery of the coolant loss.?

Low level in the plastic header thank.

Was the engine overheating,steam from the exhaust or just a service interval check?

None of those. No obvious symtoms. The engine is otherwise running perfectly.

Do you have a water temperature gauge fitted,and working?

None fitted.

Could it be back pressure within the H/E tubes, so that the coolant is not able to travel,and vents out of the cap.

I don't know - but the H/E cap seems to be a possible place to start looking. I guess this was removed when the coolant was drained and it might not be a good seal anymore - or have been not properly screwed back on!

I lost my H/E coolant by overheating ,after the impeller became blocked in the raw water system ;very noticeable too, out of the overflow pipe and into the bilge.

No - defintely not that. The raw water is pumping well. The engine is not overheating.

Shut down quickly and sailed back to a pontoon,and replaced the impeller,cleared all blockages, refilled the coolant, and back to normal after 1 1/2 hrs. I was lucky it did no damage.
ianat182

Indeed - you were lucky.

Thanks for all the suggestions everyone.

 

[TheBoatman]

Are you getting any anti freeze laying in the bilges? If not then you're loosing it internally. If you can see a/f in the bilge then try and chat up a local motor mechanic and see if he'll lend you his radiator pressure tester ~ it allows you to pressurise the system without running the engine which makes checking for leaks that much easier ~ the gauge on the tester will also confirm if you have a leak.

Peter.

 

[Blueboatman]

Just a suggestion..

You don't say whether you have a domestic hot water tank/engine heated circuit fitted.

If so, you may just need a secondary, additional expansion tank to allow for the extra 'Volume' of coolant water being circulated and heated ?

 

[westernman]

Just a suggestion..

You don't say whether you have a domestic hot water tank/engine heated circuit fitted.

If so, you may just need a secondary, additional expansion tank to allow for the extra 'Volume' of coolant water being circulated and heated ?

Yes we do have a domestic hot water tank/heat exchanger.
Could it be that the standard coolant header tank is too small and it is overflowing?

Actually, it does look as if the domestic hot water tank has leaked at some time. Not sure where the heat exchanger is - inside the tank I guess??? In which case that might be the answer.

I will try and find out if that is hot domestic water or engine coolant which has leaked. Didn't cross my mind before.

Thanks for bringing this up.

 

[westernman]

Are you getting any anti freeze laying in the bilges? If not then you're loosing it internally.

None that I can see. But I couldn't be sure that there really isn't any or it hasn't evaporated.
After all it is only 3 litres over a season and that amount would evaporate inside a couple of weeks. (It is warm/hot and mostly very dry down here).

 

[TheBoatman]

I recently had a small leak on a Yanmar YM20 that I fitted last year and despite my best efforts I couldn't find it ~ I knew I had a leak because there were traces of "green" a/freeze in the bilge after prolonged use. I finally sorted the problem by borrowing a system pressure tester and from memory the operating pressure is about 8 psi, by the time I had got about 6 psi in I could see a small trickle of a/freeze down the front casing ~ it turned out to be a hose clip on the domestic supply pipe on the top of the engine ~ I tightened it up and then jacked the system up to 13 psi without any leaks. Since then I've not lost a drop.

Take my advice and beg, borrow or steal a pressure tester because you can push the pressure way beyond what the engine will normally generate and if you have a leak that is running externally you'll see it easily ~ if there apppears to be no leak externally but the pressure guage drops you'll know the leak is internal.

Peter.