Mysterious sudden coolant dump.

VESPER

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Heres a puzzler for the brains trust.

The boat an HR94 fitted with Volvo MD22 (perkins prima) mysteriously has dump about 5l of coolant into the bilges at some point over the last few months/weeks

The boat was relaunched 3 weeks ago and on relaunch the winterization antifreeze was drained from the sea water side and the water tanks refilled etc etc. On leaving the boating I inadvertently left the calorifier immersion heater on - for just shy of 2 weeks.
This visit I had an hour so to spare so changed out the primary and engine fuel filters ran through the normal engine checks and noticed no coolant in the header tank. To refill the coolant took over 5l ! Checking the bilges located the missing coolant.

Annoyingly I cannot remember checking coolant on the initial remission- it is a check I do every time pretty much on autopilot so may well have not seen any issue. (Its great getting old!!).

Checking around the engine did not throw up any major leaks however the calorifier pipes had seeped some coolant as there was minor coolant crystallization.

My query is if the calorifier was left on could this pressurise the engine coolant to the point it would vent some 5l?

I know the freshwater side of the calorifier has an over pressure vent does the engine coolant side also have this?

Any similar experiences or specific knowledge would help.

TIA.
 

RichardS

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The only way I can see that happening would be if the engine coolant coil inside the calorifier has sprung a leak and the excess pressure inside the calorifier is pressurising the engine coolant system through the leak.

I'm still surprised that the entire contents of the coolant system have been ejected as I would have thought that the coolant filler cap in the header tank would have released the pressure.

Is there any sign that the coolant has been lost through the filler cap?

Richard
 

VESPER

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Hi RichardS thanks.

The was no sign of contamination action in the hot water side of the tank not through running the tap at least.

I did think about the filler cap as point of exit and is does look pretty tired. That's on my lost of replacements - likewise I cant see that volume being expelled either not though simple expansion.

When I refilled the engine and ran it up to temperature it held its contents??? Its got me head scratching.
 

wiggy

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My MD2020 did similar. 2 weeks later it seized. Turned out the thermostat was on its way out and eventually failed shut causing overheat and seize.
 

superheat6k

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I had a similar issue on one of my VP TAMD60Cs on my last boat. Coolant would appear in the bilge, and when checked the system was over full. I drained some out and it kept filling up. This turned out to be a pinhole in the heat exchanger - the seawater from the pump was at a higher pressure than the coolant side, so it kept filling the coolant side right up and then out of the pressure cap.

In your case though the water has drained down within the coolant side, which suggests a leak somewhere.
 

Cardinal

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YHow recently was the coolant which found its way into the bilge, added to the system? If old and weak, it may have frozen in which case your new fill is heading for the bilge too? I read that this has not happened yet but was the engine
really up to temp to pressurise the system?
 
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RichardS

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Hi RichardS thanks.

The was no sign of contamination action in the hot water side of the tank not through running the tap at least.

I did think about the filler cap as point of exit and is does look pretty tired. That's on my lost of replacements - likewise I cant see that volume being expelled either not though simple expansion.

When I refilled the engine and ran it up to temperature it held its contents??? Its got me head scratching.

Very curious. I think all you can do is keep a close eye on the coolant level, whether it's going up or down, and keep a close eye on whether there is ever the slightest trace (pink/blue/whatever) in the domestic hot water.

I think there must obviously be a leak somewhere if it's not come past the filler cap so I think it will reveal itself in due course, although it's very worrying if you need to undertake any long journeys.

Richard
 

VESPER

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Thanks all.

It looks like a hour or two in gear on its berth is order if nothing else to build some confidence....

As a side note this engine was used a lot in Landrover conversions and there they have some notoriety for head gasket failure. Which is and easy test to confirm.

I'll revert if I find anything next week.
 

dom

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Makes sense to test thermostat and then gently run in marina. If that doesn't resolve it:

1. I would be inclined to disconnect the calorifier circuit for ease of testing

2. Fit an exhaust temperature overheat alarm and monitor the relevant engine components with an infrared thermometer as engine is ramped-up.

 
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