I thought I'd share my recent experience around a sudden (almost) catastrophic loss of coolant and the reason for it. By way of background: We've had our 2008 Bav 38 (Enceladus) for just over a year. It's fitted with a D2-40B and 130 Saildrive. The engine now has 1478 hours on it and looks brand new and generally well maintained. Fuel and oil filters were dated and had the engine hours clocked up written on them when they were changed so it looked like regular servicing had been done anyway. The boat was in charter for a few years but came with no documented service history. I had it non-invasively checked by the local Volvo agent before we bought it because it had a weeping salt water pump and a very small amount of dried up antifreeze in the bilge below the muffler. Additionally, the saildrive had been overfilled with oil. I'd looked at another 38 before this one (fitted with a D2-55) and, from the invoices kept by that owner, noticed a very expensive raw water pump replacement. That, along with my Googling the effects of overfilling the saildrive unit caused some concern! I wanted to know the implications of what I'd noticed and it gave me some negotiating leverage with the vendor via the broker. The only comment the local Volvo agent’s rep gave me in his report (apart from regurgitating what I'd actually told HIM…
) was that 'it might need a pressure test at some time'.
Fast forward a year and I have it on the hard, anti-fouling before the Summer holiday here in NZ. Put the boat back in the water and decided to go for lunch at a bay an hour away. Going down the harbour I heard the engine change pitch ever so slightly. Water flow from the exhaust was fine as usual. I knocked it into neutral and idle and could then hear the ‘no water’ alarm (no temperature gauge). Off engine immediately and checked coolant. No coolant in the expansion chamber but a very hot smell! I sailed back to the marina (carried more by the tide than wind!) which allowed the engine to cool down, topped up the coolant, and started the engine only long enough to reverse down the fairway and back into the berth. Result - no coolant in the chamber and alarm just starting to go off again. Coolant was dripping from the back of the freshwater pump pulley into the bilge (but certainly not the entire contents of the expansion chamber). I figured it was ‘burping’ and self-bleeding and would just take some time to get itself sorted out but I didn’t want the freshwater pump to be dripping, so I Googled some more and got a new (non OEM) freshwater pump ordered from the UK (very reasonably priced I thought). Fitted that, took the core out of the H/E (lovely and clean but a PITA to remove as there’s not enough room in front as it hits the bracket holding the expansion chamber), fitted new o-rings to the end caps etc (not knowing when they were last done). I had removed the exhaust elbow (and air filter) in order to remove the aft end cap (the very short hose directing the raw water into the elbow is next to impossible to remove so I undid the hose clip and slid the entire elbow off without disturbing the gasket - the exhaust elbow looked quite manky. At the very end of the heat exchanger there were some greenish crystals (see photo 1). I thought salt water crystals that would blow out next time the engine ran, but I got a rag and wiped it out and then reassembled everything. No experience with Volvo motors before this and my old boat’s 1967 six cylinder marinised Ford was a completely different arrangement.
Topped the coolant up again and sat the pressure cap on top (rather than screwing it down) - coolant level stayed the same - all good. Screwed the cap down and it started disappearing again! Checked the exhaust - greenish tinge in the water and somewhat more frothy mix than usual. Took the cap off - raw water from exhaust back to being water only. Oh dear - serious issue going on (?head gasket, $$$). So my thought process was that the coolant, when under pressure, is making it into the exhaust and being pushed through the waterlock muffler and straight into the briny. Given that it’s a closed system there must be a crack or hole in the H/E. To confirm this, my mate put his jandal over the exhaust and with the cap off the expansion chamber the coolant was popping and bubbling. So, off with all the parts I’d just reassembled and off with the H/E. I also removed the exhaust elbow from the exhaust pipe and got a much better look at how manky and closed up it was (see photo 2). Imagine my surprise when I removed the exhaust gasket from the H/E and started poking around with a screwdriver when the screwdriver opened up two holes in the back of the heat exchanger (photo 3). I spoke with a marine mechanic about perhaps TIG welding the hole and putting a bead around the ‘gap’ where the exhaust gasket sits but he advised that it was not feasible. So, just before the Summer holiday the boat was going to be unusable…..emptied the boat maintenance account, sold the wife and kids, and got a new HE and exhaust elbow (none in the country so flown in within two days from Australia).
The reason I’m telling this story? If you do your own maintenance it would pay to check this area once every couple of years at least (the same time you’re replacing the O-rings in the core area). The H/E is a very poorly designed casting (and VERY expensive). I asked the mechanic what I might do to prevent this reoccurring and the only advice he could give was to ensure that the coolant was changed as per the Volvo recommendation, and with the correct grade (as the antifreeze loses its anti-corrosive properties over time). It also starts aerating more (how? Why? Not sure) – add fizzing bubbles to already compromised alloy and it starts eating away even more.
I looked at alternative material exhaust elbow replacements but for expediency just went for the cast iron unit from Volvo. Coming from a DIY background where we are used to fabricating some of our own parts, it really hurts to have to fork out big money for parts like this!
Pleased to say that I don’t think there are any other issues as a result of this event.
Cheers,
Griff
