How to fix fresh water coolant leakage Yanmar 3YM30?

[Vilja 36.7]

I have a 2008 FIRST 36.7 yacht w Yanmar 3YM30/SD-20 , sea and fresh water cooled . First trip in February, cold with snow. After 30 min at low spead, got engine overheating alarm. Surprised when found almost no fresh water/cooler in cooler tank. No water in engine oil. No signs of external leakage. What can be wrong? Is top gasket blown? Grateful for the help !

 

[Albert Ross]

Did someone drain it on laying up and forget to refill it this year?

 

[David2452]

Fill it up and run it (or pressurize it) and look for leaks as a first step.

 

[Vilja 36.7]

No. The coolant was replaced 4 years ago (by Yanmar dealer). After this, I have (only) checked the level in the recovery tank, and that level has been OK. Yesterday, I filled it up and ran the engine at idle for 30 min. Then alarm for overheating again. When checking after the engine had cooled, once again no coolant in the tank. So substantial leak. I can check whether coolant appears with seawater in the exhaust.

 

[charles_reed]

Unfortunately filling up the overflow tank on the 3YM doesn't fill the main system.

You need to wait till the engine is cold, take off the pressure-cap on top of the heat-exchanger and then fill that up to the brim (with ready-mixed coolant).

It takes a few repeats of the exercise to fully fill the system, especially if you have a calorifier in the circuit.

My reading of your situation is:-
a) the coolant level has fallen too low
b) the belt, running alternator and main coolant pump may be slipping.
c) (most unlikely), the cooling system is being pressurised by a leaking head-gasket and being emptied.
I'd be most surprised, in the latter case, that you hadn't noticed the dye in the ejected coolant around the engine bilge.

 

[RichardS]

Unfortunately filling up the overflow tank on the 3YM doesn't fill the main system.

Charles - this is the relevant section from my 3YM30 manual

(5) Check and Re-supply Fresh Water

Check the fresh water level before operation while the engine is cold.
Checking the water level while the engine is hot is dangerous, and the cooling water reading will be misleading due to thermal expansion.
Check and supply cooling water routinely at the coolant recovery tank only.

It goes on to explain, in slightly mangled English, that you should only add coolant through the pressure cap if the recovery tank has been allowed to become completely empty. Whilst this is the case with the OP, it is not normally necessary to remove the pressure cap.

Richard

 

[[3889]]

When you say no signs of leakage do you mean in engine bay? Have you checked calorifier if fitted? Mine drains to main bilge sump and leaking coolant would be removed by float-switch pump.

 

[Vilja 36.7]

How to fix leakage

When you say no signs of leakage do you mean in engine bay? Have you checked calorifier if fitted? Mine drains to main bilge sump and leaking coolant would be removed by float-switch pump.

Thanks for you thoughts! When I left the yacht, I noted some (around 100 mL) fluid in the bilge, coloured, so could be coolant mixed with oil (?). It might have arisen when i exchanged oil filter. Since the volume seemed small, I did not suspect that to be coolant. Could this be a lead?

As for calorifier, do you mean heat exchanger for hot water in the sink? If so, there is one (Quick model). Due to electrical short cut last Autumn when using it by land current, I thought the element was gone and replaced it with a new one. When I removed the water in the Quick tank, I did not notice any colour indicating coolant. It has been functioning normally (water heats) when engine is running.

 

[Halo]

I had something similar last year
It turned out to be a leak on the water pump
The fix was a new pump

 

[Vilja 36.7]

Calorifier and bilge

Unfortunately filling up the overflow tank on the 3YM doesn't fill the main system.

You need to wait till the engine is cold, take off the pressure-cap on top of the heat-exchanger and then fill that up to the brim (with ready-mixed coolant).

It takes a few repeats of the exercise to fully fill the system, especially if you have a calorifier in the circuit.

My reading of your situation is:-
a) the coolant level has fallen too low
b) the belt, running alternator and main coolant pump may be slipping.
c) (most unlikely), the cooling system is being pressurised by a leaking head-gasket and being emptied.
I'd be most surprised, in the latter case, that you hadn't noticed the dye in the ejected coolant around the engine bilge.

Thanks for you help! See below regarding bilge and calorifier. I will try and fill up more and see what happens. I still wonder why I could fill 3.5 litres in the coolant tank that holds around 5 litres and after running at idle, low level again. Maybe 5 litre capacity is without calculating the calorifier?

 

[[3889]]

Yes, I made the mistake of not including the calorifier loop when refilling with coolant -it takes about an extra 3l of fluid. If you replaced the immersion coil I would check that joint for possible leaks, though I don't think it should affect the coolant side of the system.

 

[charles_reed]

Thanks for you help! See below regarding bilge and calorifier. I will try and fill up more and see what happens. I still wonder why I could fill 3.5 litres in the coolant tank that holds around 5 litres and after running at idle, low level again. Maybe 5 litre capacity is without calculating the calorifier?

My 3YM and calorifier holds 9.5 litres - it all depends on how far the feed pipes wander. I did have a leak - one of the coolant feeds had rubbed against the propshaft producing a minute leak, but only when the sytem was fully pressurised. That took quite a long time to find, because the coolant evaporated almost immediately.
Immense patience and a considerable healthy scepticism regarding "received" wisdom are required about anything to do with boat engines, their electrics and anchoring.

 

[charles_reed]

Charles - this is the relevant section from my 3YM30 manual

(5) Check and Re-supply Fresh Water

Check the fresh water level before operation while the engine is cold.
Checking the water level while the engine is hot is dangerous, and the cooling water reading will be misleading due to thermal expansion.
Check and supply cooling water routinely at the coolant recovery tank only.

It goes on to explain, in slightly mangled English, that you should only add coolant through the pressure cap if the recovery tank has been allowed to become completely empty. Whilst this is the case with the OP, it is not normally necessary to remove the pressure cap.

Richard

I've found that advice to be thoroughly misleading, having one filled from scratch, the indirect system and once replaced the coolant in the system.

 

[cliff]

To save the cost of anti freeze use tap water dosed with drain tracing colourant containing fluorescein then search for leaks with a black light