Yanmar 4JH3-TE coolant overflow

[Irish Rover]

I noticed recently that the level of coolant in the expansion bottle on one of my engines was above the max level when the engine was cold. I was fairly sure it hadn't been like that previously but I wasn't certain so I took a small amount out with a drill pump and left it just below max. After running the engine for about 4 hours at the weekend I checked it yesterday and it was above the max again and some had actually overflowed. I'm not much of a techie but I'm assuming I have a problem - presumably seawater getting into the closed system. How serious is this and what do I need to do to fix it - can it wait a few weeks as I have family visiting for the next couple of weeks and they will be disappointed if the boat is out of action. Any advice appreciated.

 

[RichardS]

Probably a leak across the heat exchanger. If it's just an O-ring then should not be difficult to replace but if it's a perforation in the core then a new part is probably the best answer. If it's not too bad you could wait, although, if it were me I would start topping up with undiluted antifreeze to keep the concentration high and prevent the salt causing too much corrosion in the cooling circuit.

Richard

 

[VicS]

I noticed recently that the level of coolant in the expansion bottle on one of my engines was above the max level when the engine was cold. I was fairly sure it hadn't been like that previously but I wasn't certain so I took a small amount out with a drill pump and left it just below max. After running the engine for about 4 hours at the weekend I checked it yesterday and it was above the max again and some had actually overflowed. I'm not much of a techie but I'm assuming I have a problem - presumably seawater getting into the closed system. How serious is this and what do I need to do to fix it - can it wait a few weeks as I have family visiting for the next couple of weeks and they will be disappointed if the boat is out of action. Any advice appreciated.

As well as looking at the heat exchanger for leaks it might also be worth checking the water injection point into the exhaust for partial blockage causing an increased pressure in the seawater circuit. Normally the coolant pressure will be higher that the seawater pressure at least at normal operating temperature which would lead to loss of coolant into the sea water side of the HE in the event of a leak, not an apparent gain of coolant.

 

[Mistroma]

As well as looking at the heat exchanger for leaks it might also be worth checking the water injection point into the exhaust for partial blockage causing an increased pressure in the seawater circuit. Normally the coolant pressure will be higher that the seawater pressure at least at normal operating temperature which would lead to loss of coolant into the sea water side of the HE in the event of a leak, not an apparent gain of coolant.

+1 I thought the same thing, why would seawater enter the coolant side as that's usually at a much higher pressure? Only other thing I can think of would be a head gasket leak as that would over-pressurise the coolant side and force coolant out. However, OP hasn't mentioned other problems and surely a head gasket leak would lead to other problems due to coolant leaking through head gasket after engine stopped. That would likely show up as starting problem (or worse), overheating, water in oil etc.

1) Blockage in water injection point AND leak in exchanger.
I prefer a single failure rather than 2 as the simpler option is usually more likely. However, I can see increased back pressure leading to failure in a seal being pushed in opposite direction. The seals would be designed to withstand pressure generated in the coolant system. First failure then makes second one more likely.

2) Head gasket leak
Single failure explains the symptoms. However, other associated issues aren't mentioned. I suppose it could be a very recent failure and quite small. Even so, pressure would still cause slow loss of fluid into cylinder after engine has been stopped.

Not really completely convinced about either of the above but am leaning towards VicS's explanation unless OP has other symptoms.

 

[Irish Rover]

Thanks for the replies. There are no other symptoms that I’m aware of - the engine starts first turn same as it’s compatriot and oil on the dipstick looks fine. The only thing to add is the coolant colour in the expansion bottle looks black whereas on the other engine it’s green.

 

[RichardS]

2) Head gasket leak
Single failure explains the symptoms. However, other associated issues aren't mentioned. I suppose it could be a very recent failure and quite small. Even so, pressure would still cause slow loss of fluid into cylinder after engine has been stopped.

I would be surprised if a head gasket leak would cause the coolant level to be raised above the normal level once the engine had cooled down. I think it would be more likely to cause a temporary increase whilst the engine was running due to overheating and/or over-pressurising (which would also cause other effects). However, once the engine had cooled the level would probably be lower than before due to the loss of coolant from the overflow.

A continuing increase in coolant level over several hot/cold cycles must surely be due to sea water ingress and the heat exchanger is presumably the only interface.

Richard

 

[Mistroma]

I would be surprised if a head gasket leak would cause the coolant level to be raised above the normal level once the engine had cooled down. I think it would be more likely to cause a temporary increase whilst the engine was running due to overheating and/or over-pressurising (which would also cause other effects). However, once the engine had cooled the level would probably be lower than before due to the loss of coolant from the overflow.

A continuing increase in coolant level over several hot/cold cycles must surely be due to sea water ingress and the heat exchanger is presumably the only interface.

Richard

Good point. However, I still don't see why a seal failure would normally cause seawater to leak back into an engine when it is running. Surely pressure would cause the leak from coolant side to seawater side. Are you saying that coolant system normally runs at lower pressure than the seawater side? Or are you agreeing with VicS about possible reason for pressure difference? This information would be useful to OP.

I see that OP now says coolant is black instead of green. Might that be from exhaust side as per VicS's comment about a restriction in that area?

 

[VicS]

Thanks for the replies. There are no other symptoms that I’m aware of - the engine starts first turn same as it’s compatriot and oil on the dipstick looks fine. The only thing to add is the coolant colour in the expansion bottle looks black whereas on the other engine it’s green.

Dont like the sound of that !

Maybe suggests a head gasket failure but I am sure you'd notice the engine not running quite right.

Maybe there is more salt water in the coolant circuit than you realise and that it is already causing corrosion.

 

[Keith-i]

Whilst I tend to agree with the above posts one further possible scenario is a defect in the calorifier coil allowing domestic fresh water to enter the cooling system. I think this is unlikely given the typical pressure differences and the colour change noted. Sounds more like a head gasket failure but that doesn’t explain the rise in level once cool.

 

[RichardS]

Good point. However, I still don't see why a seal failure would normally cause seawater to leak back into an engine when it is running. Surely pressure would cause the leak from coolant side to seawater side. Are you saying that coolant system normally runs at lower pressure than the seawater side? Or are you agreeing with VicS about possible reason for pressure difference? This information would be useful to OP.

I see that OP now says coolant is black instead of green. Might that be from exhaust side as per VicS's comment about a restriction in that area?

I agree with you and Vic that coolant pressure would normally always be higher than seawater pressure in the heat exchanger so normally I would expect the flow to be in the other direction. Vic's suggestion of a partial blockage causing elevated seawater pressure seems the most likely explanation .... but whatever the explanation, I just cannot think of any other place other than the heat exchanger for the transfer of water-based fluids to take place.

I also wonder whether the black colour is caused by salt attacking the iron inside the engine, simply because I can't think of any other explanation but whether salt could cause this effect so quickly when some coolant is presumably still present is something I don't know.

Richard

 

[RichardS]

Whilst I tend to agree with the above posts one further possible scenario is a defect in the calorifier coil allowing domestic fresh water to enter the cooling system. I think this is unlikely given the typical pressure differences and the colour change noted. Sounds more like a head gasket failure but that doesn’t explain the rise in level once cool.

Good point. That is another interface if a calorifier is fitted. In fact, it's possibly a more likely explanation since the freshwater side of the calorifier will be pressurised by the domestic water pump and could certainly enter the coolant stream before the engine is up to temperature. However, this doesn't explain the black colouration unless the anti-corrosion level has gone very low. Perhaps the black is a coincidence?

Richard

 

[duncan99210]

Good point. That is another interface if a calorifier is fitted. In fact, it's possibly a more likely explanation since the freshwater side of the calorifier will be pressurised by the domestic water pump and could certainly enter the coolant stream before the engine is up to temperature. However, this doesn't explain the black colouration unless the anti-corrosion level has gone very low. Perhaps the black is a coincidence?

Richard

The symptoms match those I had. A taste test proved the coolant was not sea water contaminated and replacing the calorific stopped the problem.

 

[Irish Rover]

Thanks again for all the information. I will try the taste test when I go to the marina later. Will there be a way to isolate the calorifer from the fresh water system?

 

[VicS]

Thanks again for all the information. I will try the taste test when I go to the marina later. Will there be a way to isolate the calorifer from the fresh water system?

Probably not but its worth checking the supply to it for a valve.

There may or may not be valves to isolate it from the engine coolant circuit.

In the absence of both it will probably be easier to disconnect from the fresh water system and blank off the connection so that you can still use the cold water.

 

[Mistroma]

Good point. That is another interface if a calorifier is fitted. In fact, it's possibly a more likely explanation since the freshwater side of the calorifier will be pressurised by the domestic water pump and could certainly enter the coolant stream before the engine is up to temperature. However, this doesn't explain the black colouration unless the anti-corrosion level has gone very low. Perhaps the black is a coincidence?

Richard

Makes sense what you said about pressure differential between coolant and sea water. I was only probing further as a mechanic might just be told to fix a heat exchanger leak without thinking what could have caused it. At least OP now knows back pressure from sea water side isn't the normal condition.

Calorifier leak is possible as you say but I thought most are stainless and don't think it would give a black colour either. If water is coming from the calorifier you wouldn't get corrosion from inside that item. Good point about dilution of coolant leading to corrosion inside the block etc. but OP didn't indicate a huge long term leak. My feeling is that replacement of a litre or two with fresh water wouldn't leak to rapid production of "black rust".

I agree with you that the black colour is difficult to explain. Perhaps OP hasn't accurately described the amount of coolant lost (doesn't sound like it though). I'm not a great believer in coincidence and would treat the black colouration being linked to the issue.

Calorifier issue is well worth considering but I don't think it is a good match for the symptoms. But nothing we've discussed is either and that's always the difficulty with remote diagnosis.

 

[Irish Rover]

I’m at the boat and I’ve done a bit of investigation based on the replies and advice above. First off about the colour the bottle seems to be discoloured on the inside but when I took a sample of the liquid inside it seems to be clear clean liquid with a slightly sweet taste. If I had to guess now I’d say the coolant is diluted to the stage of being nearly water unless of course the water has just risen to the top. I completely cleaned the bilge and I’d estimate there was less than a liter there but that’s not to say the pump hadn’t operated at some stage.
The water heater is a Di Mariano 22L which appears to have been in the boat from new - the boat is 2003 and the heater was manufactured in 06/01. There are 4 hoses connected to the tank - one blue one red and 2 yellow/black. The blue hose has a tap on it and when I close it the hot water supply to the taps is cut. I’ve left that closed for now and reduced the level in the expansion bottle just below max. Am I safe in assuming that if the level in the bottle is not higher after my next trip and there are no more overflows that the problem is the water heater?
I have a couple of other questions I’ll post later but I’d be grateful for any words of wisdom based on this information.

 

[RichardS]

The tap has closed the flow of fresh water either into or out of the calorifier .... but it depends whether the tap is on the inlet or output side. If its on the inlet then once you open a hot tap all the pressure will be relieved in the calorifier and no water should be forced into the coolant. If it's on the outlet side, then opening a hot tap will relieve the pressure in the hot water pipework but the calorifier itself will still be pressurised by the fresh water pump.

Is there anything to indicate inlet or outlet? If not, you could crack open a fitting slightly and see whether the calorifier is still pressurised or there is probably a pressure relief valve with a small handle or knob which can be cracked open manually. If water comes out under pressure when it the handle is pushed and the fresh water pump kicks in then the tank is still pressurised even though the tap is off.

Richard

 

[duncan99210]

Usual water system colours are red from hot water, blue for cold. So, it there’s a tap on the blue hose it most likely to be the cold water supply to the calorifier whilst the red hose is the outgoing hot water supply. Therefore turning the valve on the blue hose off will depressurise the calorifier and thus stop the leak into the engine coolant.
Once you’ve resolved the calorifier problem, drain the coolant and replace with the proper stuff; not because it’ll freeze in Turkey but because the “antifreeze” also has an anti corrosion function.

 

[vyv_cox]

When I assisted Carmel 2 with this problem and wrote it up for PBO my test was simply to monitor the level of coolant in the overflow bottle while the domestic water pump was switched on. In the time we took to drink a beer the level had risen significantly. It turned out that the heating coil inside the calorifier was perforated.

The alternative already discussed, of seawater entering via the heat exchanger, has come up quite a few times with Volvo 20x0 engines but not with Yanmars that I recall. Yanmar manifolds tend not to foul with carbonate salts to the same extent. There's always a first time though...

 

[Keith-i]

There are 4 hoses connected to the tank - one blue one red and 2 yellow/black. The blue hose has a tap on it and when I close it the hot water supply to the taps is cut.

The black/yellow hoses are probably the coolant hoses from the engine to the calorifier coil. Closing the cold water feed to the calorifier should test the theory about the domestic water entering the coolant circuit. The belt and braces approach would be to pull the fuse for the domestic water pump too. Discoloured coolant bottle sounds like oil/gases from engine combustion have entered the system i.e. head gasket problems.