Engine coolant pre-heater and use in the UK?

[FionaJC]

I am about to change my engine which seized over lockdown - that's another story. My engine heats the hot water by the addition of a calorifier. The cabins are heated with a Chinese diesel heater which has been great. I now have a spare Webasto 5Kw water heater.

I thought I would replace the air heater with the Webasto, add a couple of fans to the circuit with some valves to choose what I heat and I thought why not preheat the engine? So I will have a lot of pipes running with engine coolant (not good but don't worry, I am including cut off valves.)

I'm then thinking if I can heat water or air with either the engine or Webasto, why not add pre warming the engine? I can do this with an extra valve and a by-pass pipe (brown) in the picture below.

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I live on the east coast of the UK and when there are cold winters (>-5C) i'm at home with a log fire and a duvet. So I wont need it to start the engine.

My question is? Will it be good for my old Perkins 4107. It will warm the block, melt the oil so it starts easily and with runny lubricant reduce wear or am I wasting my time? I can put in plenty of interlocks and protection but doing it this way I can use the engines expansion bottle too.

[GordMay]

Why not?
Improves engine [cold] starting, and helps eliminate "white smoke", at start-up.

[tkeithlu]

Go for it. Your oil will do a better job on startup, and as Gord says, starting will be easier. The only design element I'd be concerned for is making sure that your engine circulating coolant can get up to operating temperature. Suck off too much heat during the engine operation phase and you'll be perpetually running a cold engine.

[FionaJC]

Originally Posted by tkeithlu

Suck off too much heat during the engine operation phase and you'll be perpetually running a cold engine.

That's a good point but its also why I'm doing valves and things. My engine control panel is computer controlled so that's why I say I have interlocks etc. The Calorifier and fan only activate after the thermostat has opened.

I'm also thinking about a plate heat exchanger between the engine and webasto but it means more pumps and header tanks so I'm trying to keep to the KISS principle while giving me all the options.

I don't need coldstart as it starts cold in one second, I really just want to minimise wear with warmer oil.

[rslifkin]

I personally like the heat exchanger option. It means less parts in the engine cooling loop (although you'd need an electric pump in the engine loop to enable pre-heating). And that means a failure in the hydronic heating loop somewhere doesn't disable your engine. You could also limit the size of the heat exchanger to limit the amount of heat taken from the engine coolant if desired.

[goboatingnow]

I would agree , I’d be concerned about long runs of engine coolant.

A heat exchanger with a thermostat would allow the engine to get up to temp etc.

Given you have hot air heating , it’s all very elaborate , personally i wouldn’t bother. The benefits are very limited , if you want to heat the engine get a block heater

[FionaJC]

Thanks for all your comments.

Just had a conversation with someone I know who is up high in tecnhical areas from Case New Holland.

Wear in the UK will be minimal hot or cold, and the coolant will not heat the oil up much as its in the sump and its the block thats warm so potentailly I am going to put cold oil round a warm engine and could induce other stresses.

As he said, its not likely to be -40C like Canada.

So Ive decided to go with either engine / webasto heating and leave engine pre-heating out of it.

[Jammer]

Originally Posted by FionaJC

Thanks for all your comments.

Just had a conversation with someone I know who is up high in tecnhical areas from Case New Holland.

Wear in the UK will be minimal hot or cold, and the coolant will not heat the oil up much as its in the sump and its the block thats warm so potentailly I am going to put cold oil round a warm engine and could induce other stresses.

As he said, its not likely to be -40C like Canada.

So Ive decided to go with either engine / webasto heating and leave engine pre-heating out of it.

Mostly true.


I live in Minnesota where it gets to -25 F. Used to have diesel equipment for snow removal and things.


A diesel in good condition should start OK without any particular effort or special measures down to around 20 F or so. Glow plugs, manifold preheat, or fuel bypass will drop that to around 5F. Below that, a preheat is useful.


Generally the main goal of preheating the engine is to warm up the cylinders to the point where the engine oil film on the cylinder walls produces less friction during starting, so that the engine will crank faster. It also helps starting by increasing the overall temperature of the engine assembly so that the fuel-air mixture will ignite.