Now, the rest of this post is boring maintenance information. Normal folks should now stop reading and do something mind improving.
That evening, the captain noticed that the main engine had spat a little coolant into the overflow bottle. Hum. Upon checking the header tank, the bad news unfolded. There was a little clean oil on top of the coolant in there. Grr. Luckily the engine had decided to wait for the end of the cruising season to play up and as the engine is keel cooled, diagnosis is pretty simple: the O rings in the gearbox oil cooler have almost certainly started to leak a little, allowing gearbox oil under high pressure to get into the coolant. The big questions is, how much?
Well, after cleaning out the slightly contaminated header tank, the coolant that was drained from the engine block was fine. No nasty emulsified stuff at all - seems we were lucky that it chose to fail on a shorter run. A little cleaning and perhaps flushing with some dishwasher detergent in the system, a coolant change and all should be well. Just the small matter of changing the O rings in the cooler to contend with. We had the spares on board for such an eventuality too. Perhaps we should have changed them last winter as a preventative thing? Well, on keel cooled engines they are supposed to last many more hours than we have recorded so far but lesson learnt. They are now on our routine maintenance list a little more frequently than before!
Whilst the coolant level was low, the thermostats got changed too. Here are the two new ones cuddled up in their housing:
Michael, who owns Coracle, a Nordhavn 40, intends to replace his oil cooler O rings as a preventative job this winter. Hence he came along to help and so we discovered the challenges together.
Draining down the coolant via the drain fitting on the engine block was a slow process. It resulted in some suspicious looking bags:
If you remember the story of the Liverpudlian that we bumped into at Fort William, then you will see how the sight of these brought back some unpleasant memories. The John Deere pre-mix coolant is an unfortunate colour.
The next challenge is removing the coolant pipe from the bottom of the oil cooler without drowning the small alternator. It sits in just the wrong spot and so some large plastic bags were taped into position to protect it as the hose was gently released and the residual coolant leaked out. Alternator saved, the cooler itself was removed:
and then we found the next challenge - a normal Allen Key will not undo the top end cap as there is not enough space to get it into one of the three fixings. Nothing in the tool box was going to work but luckily Michael had an extensive Dremel kit on his boat and so we cut down an old Allen key to suit. This is now an important part of our toolset!
The end caps came off relatively easily to reveal the tubestack and the offending O rings:
Nice gloves though....
The tubestack had a good clean up and then, after cleaning the casing, the work hit trouble. there were what looked like some form of stress cracks in the casing itself. Two thin ones along the length of the cooler and three smaller ones around the body - all of these were hidden between the cooler and engine when it was in position.
There had been no leaks evident (oil would be coming out under pressure onto the cooler surface) but it looked suspicious. There were two choices - get it tested by a professional outfit with the right kit or replace it. A new casing was amazingly sensibly priced via ASAP Supplies at a lower cost than a test would be so new parts were duly ordered. In fact we went wild and got a whole new cooler as that was as cheap as ordering a casing and tubestack individually. Having a spare tubestack seemed sensible somehow. The new cooler duly arrived:
was dismantled and the original end caps were fitted as they have different outlets. We also used the new O rings from Alaska Diesel, the Lugger people, rather than the ones supplied with the Bowman cooler itself. Apparently they have sourced a different material that is more forgiving of assembly issues and more durable. Let's see if they can survive a ham-fisted captain.
Of course, having a brand new tubestack means that the one we had carefully cleaned out is now a spare. Still, it had to be spruced up..........
A new coolant hose was procured and then the whole thing rebuilt. Here is the oil cooler free engine adorned with plastic bags to protect the alternator:
And with the new cooler casing, tubestack and hose:
Coolant gently refilled, gearbox oil level adjusted, we fired it up to check for issues.
Guess what...... Luck was on our side and it all looked OK. Will need to take the boat for a run and get it seriously warm to prove the point but so far, so good.
