Coolant loss - Volvo D2 55

dunedin

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Engine is circa 7 years old and has run trouble free (except for saildrive blockages with shellfish) to date.

Over the winter the engine has been little used, and mainly just tick over pottering in and out of the marina. So yesterday decided to give the engine a bit more of a run when coming back in. Engine had been running gently for 10 minutes x 2 so nicely warmed up, and water flow normal.
So ran it at full throttle for about 2 minutes, 2,000 rev cruise for 5 then full for another minute before reducing revs to come back into marina.

When did engine checks before leaving boat was very surprised to find about a pint of clean blue coolant in the engine tray. Never lost coolant before. Carefully restarted, expecting to find water coming out from a split hose or damaged connection, but no further leakages spotted (access not brilliant on heat exchanger side, so not detailed checks, but no flow or drips.

Any suggestions of potential causes and diagnostic checks?
 

Bobc

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Do you have an expansion tank?

If not, it may just be fluid expansion that has relieved itself through the little rubber pipe that comes from the side of the tank by the cap.
 

Plum

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Engine is circa 7 years old and has run trouble free (except for saildrive blockages with shellfish) to date.

Over the winter the engine has been little used, and mainly just tick over pottering in and out of the marina. So yesterday decided to give the engine a bit more of a run when coming back in. Engine had been running gently for 10 minutes x 2 so nicely warmed up, and water flow normal.
So ran it at full throttle for about 2 minutes, 2,000 rev cruise for 5 then full for another minute before reducing revs to come back into marina.

When did engine checks before leaving boat was very surprised to find about a pint of clean blue coolant in the engine tray. Never lost coolant before. Carefully restarted, expecting to find water coming out from a split hose or damaged connection, but no further leakages spotted (access not brilliant on heat exchanger side, so not detailed checks, but no flow or drips.

Any suggestions of potential causes and diagnostic checks?

Have you recently topped up or changed the coolant? If so, maybe you put too much in so not enough airspace above the level. If this is the case, the level may now be correct so you will not lose any more.

Www.solocoastalsailing.co.uk
 

Bobc

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Also, giving the boat a good blast at full throttle will get the engine quite hot. If you don't usually do this, the extra heat will make the coolant expand more, hence dumping the excess.

As said above, the header tanks don't want to be brimmed. Usually just enough to cover the tube element is about right.

Most people (including me) strap an empty water bottle in the engine bay with the overflow pipe going into it to catch the excess fluid.
 

ashtead

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It can do that but normally the amount of coolant in the empty bottle as per post 4 is quite small and certainly less than a pint . Why is the coolant blue I always thought volvo needed green?
 

peteK

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More than likely it will be the rubber end caps leaking, the salt water forcing its way into the coolant side thus forcing out the coolant usually worse at higher revs.I have had it happen.
 

pvb

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More than likely it will be the rubber end caps leaking, the salt water forcing its way into the coolant side thus forcing out the coolant usually worse at higher revs.I have had it happen.

The D2-55 doesn't have rubber end caps.
 

RichardS

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It can do that but normally the amount of coolant in the empty bottle as per post 4 is quite small and certainly less than a pint . Why is the coolant blue I always thought volvo needed green?

I seem to have built up a stock of different coloured coolants over the years; clear, yellow, pink, orange, green ..... such that I though I had all bases covered. Last week I needed to top up a Honda motorbike and a Mazda sports car and these both come with blue and that was a colour I didn't have on the shelf.

Both need OAT LongLife coolant so I bought the Honda version and used it for the Mazda as well. This doesn't mean that all recent blue coolant is OAT but I suspect that it might well be.

Richard
 

dunedin

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Thanks for all of the replies.

There doesn’t seem to be an expansion tank on this installation (though had one on last boat with Yanmar). It is exactly as factory delivered. Would there normally be an expansion tank with a D2 55?

I checked the coolant level at the service in November. But not topped up recently. In fact don’t think it has needed any top ups since coolant was changed circa 2-3 years ago. And so must have done 500 hours or so, including some long hot runs, in that period.
Coolant looked blueish, but I see was Volvo Green non-OAT that I had put in previously.

No idea what end a “rubber end cap” would be on? But pvb’s post suggests I don’t need to worry?

So still a bit of a mystery why should suddenly lose coolant with a 10 minute brisk run,only 2 x 2 minutes at full revs, when have never lost any at all in previous 500 hours.
 

black mercury

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I think you are going to have to run engine again and see what happens, after topping up the coolant. Do you have a temperature gauge or just an overheat alarm? No, as said you don't have rubber end caps on heat exchanger. It may be worth taking off the end plates of the heat exchanger to make sure the tubes are all clear in case there is a partial blockage causing engine to run slightly hotter. You don't need to remove the tube stack. But as already said, with the engine running flat out it has experienced higher temperature than normal which could cause further expansion of coolant which will spill off from the heat exchanger, although a pint more than I would expect. An expansion tank would have been an option when engine was new. I think you need to try engine again and see what develops.
 

XDC

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Thanks for all of the replies.

There doesn’t seem to be an expansion tank on this installation (though had one on last boat with Yanmar). It is exactly as factory delivered. Would there normally be an expansion tank with a D2 55?

I checked the coolant level at the service in November. But not topped up recently. In fact don’t think it has needed any top ups since coolant was changed circa 2-3 years ago. And so must have done 500 hours or so, including some long hot runs, in that period.
Coolant looked blueish, but I see was Volvo Green non-OAT that I had put in previously.

No idea what end a “rubber end cap” would be on? But pvb’s post suggests I don’t need to worry?

So still a bit of a mystery why should suddenly lose coolant with a 10 minute brisk run,only 2 x 2 minutes at full revs, when have never lost any at all in previous 500 hours.

Whatever you do don’t fall into the trap of putting yellow coolant in if you’ve got green already. The block needs a flush even if you think you’ve drained the green out.
 

Bobc

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The expansion tank is an option, not standard.

Top it up, put the overflow pipe into a bottle, and then give it another run.

If there is water in the bottle, then it's no problem. If there is coolant in the bilge, check for moisture under the water pump, as the pump seal might have gone.
 

dunedin

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The expansion tank is an option, not standard.

Top it up, put the overflow pipe into a bottle, and then give it another run.

If there is water in the bottle, then it's no problem. If there is coolant in the bilge, check for moisture under the water pump, as the pump seal might have gone.

Thanks, yes that seems like a good strategy before doing anything more advanced.
 

dunedin

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Whatever you do don’t fall into the trap of putting yellow coolant in if you’ve got green already. The block needs a flush even if you think you’ve drained the green out.

Thanks. yes I am aware of the imperative not to mix OAT and non-OAT coolants. I checked carefully the age of engine and current spec before using the nonOAT stuff when changed last time, and have plenty in stock. But a very helpful reminder as that could be a good way to create a proper problem if done wrong !
 

dunedin

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I think you are going to have to run engine again and see what happens, after topping up the coolant. Do you have a temperature gauge or just an overheat alarm? No, as said you don't have rubber end caps on heat exchanger. It may be worth taking off the end plates of the heat exchanger to make sure the tubes are all clear in case there is a partial blockage causing engine to run slightly hotter. You don't need to remove the tube stack. But as already said, with the engine running flat out it has experienced higher temperature than normal which could cause further expansion of coolant which will spill off from the heat exchanger, although a pint more than I would expect. An expansion tank would have been an option when engine was new. I think you need to try engine again and see what develops.

Thanks also. Yes will investigate further and revert back.
No temperature guage, just the standard Volvo panel which may have an overheat alarm, but never heard one. Have got a separate laser temperature sensor can use to check things.
Re the "rubber end caps", I didn't really say I don't have them - as I have no idea what these are. But prv said they aren't on this engine model. In the absence of any other info, cant be definitive. Do the end plates of the heat exchanger come off without removing the heat exhanger. Not at boat currently so cant visualise this (and access on that side is very poor).
 

black mercury

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Yes the end caps will come off without removing the whole heat exchanger. You will either have three bolts or four bolts holding them on, they have a gasket and rubber o ring behind, if you're careful you might get away without having to replace them if you're only removing the end plates. A mirror may be needed for the rear one if access is tight.
 

dunedin

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So back at the boat yesterday.

Slightly worryingly, the coolant level was at normal level, whereas should have been lower having lost some coolant and then cooled down.
Is there a way of testing for any salt water in there?

Fitted a pipeway from the overflow nipple, just under the water filler cap, and fed into a bottle.
Ran for 20 minutes, in reverse gear whilst still at the pontoon, including a minute or so as near full throttle as I dared without pulling marina cleats off. No overflow in either bottle or engine tray. So still a bit confused.

Also looked for any "end caps" but failed to recognise them. Will "read the flippin manual" and see if I can identify them and/or post a couple of photos on here once downloaded them.
 
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