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Engine temperture

My Shire 50 diesel engine dose not seem to reach what I think is it's normal operating temperature of 82degrees. Checking with thermocouple probe the max temp I can detect is 60 degrees after running the engine for 90 minutes. I have removed the thermostats (2) and checked by heating in a sauce pan and both proved okay. Can you help!

Asked by: Nick  | 7.22pm, Wednesday 4 March

WW says:

The first thermostat should open around 60C to allow the coolant to flow around the the calorifier circuit. Then, once the temperature rises further, the second thermostat opens to allow coolant to flow to the skin cooling tank.
It may be that, with slow running, until the calorifier comes up to full temperature, the engine temperature may not rise above the setting of the first thermostat. If after an couple of hours cruising (with the engine under load) the engine temperature has not risen, then it may be that there is either an issue with all coolant being pumped into the skin tanks.
You may need to check the layout of the engine coolant plumbing, in case it has been set to miss the second thermostat. It is possible for the calorifier connections (especially if a hot water calorifier is not fitted) so that coolant leave the first thermostat and return to bypass the second- so allowing coolant to pass to the skin tanks when it shouldnt. The Shire 50 is a large block, so it should warm up fairly quickly when under load- I would check with the engine under cloud (ie cruising) and also then check the plumbing layout and where connections are made on the engine. Sometime blanking plugs are missing, depending on the age of the engine, which could lead to a short circuit.

Mark Langley  | 9.49PM, Wednesday 4 March

The Barrus Shire 50 has a cooling system with two thermostats that operate at different temperatures. The initial warm up of the engine is aided by heat recovery from the exhaust, after which the first thermostat opens at 71C letting hot coolant around the calorifier circuit. When the calorifier is hot, the second thermostat opens at 88C letting the coolant around the skin tank to cool the engine.
The engine temperature should therefore be between 71 and about 90C, but if the calorifier is large this will probably absorb most of the engine heat at low speeds.
You do not say what sort of boat the engine is fitted into, but the engine will be very lightly loaded in a narrowboat for canal cruising, but would work harder in a larger boat on a river generating more heat.

Rupert Smedley  | 10.05PM, Wednesday 4 March

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