Automotive-type heater (bus heater) on sea water cooled engine

[ColIn Ferguson]

Greg,

This is a raw water cooled engine so there is not a heat exchanger and closed pressurised system as in a D2 series engine.
The problem is that air gets into the manifold from the exhaust when it cools and then enters the calorifier piping on start up.
Not sure how an expansion tank would help.

Regards

Colin

[Stu Jackson]

Originally Posted by ColIn Ferguson

I have fitted a calorifier to a Volvo 2002 that is raw water cooled. The main problem has been getting air locks on the circuit.
The problem is that as the engine cools water falls down out of the manifold so when starting up again and reaching operating temperature, as the thermostat opens, air is pumped through the piping. This the
N causes the engine to overheat as coolant flow is stopped.
The solution has been to put in a second direct circuit to run the coolant as normal until operating temperature is reached before opening the circuit to the calorifier. You then need to shut off the calorifier circuit before stopping the engine so the circuit remains primed before restarting from cold.
I have incorprated electric valves wired to a switch in the cockpit to open and close the circuits.
A complex problem but i think you will have the same issues with an air heater installation.

What you need is an automatic air vent. These are used in standard commercial heating systems all over the world.

[Shaneesprit]

If you buy an air vent don’t buy the cheapest type which is about 3inch tall x 1inch wide approximately, almost any other would probably be better, the amount of those 1/2 bsp air vents I have seen failed ��.branded or not

[ColIn Ferguson]

Tried an air vent - did not work reliably. Placed it at several different points in the circuit but not good enough to allow safe engine running.
The system I have ended up with of two separate circuits with electric valves to switch once up to temperature works fine but is a bit complicated with too many junctions involved.

[Shaneesprit]

There is no reason that you can’t leave an air vent in, I have used endless amounts of them, quality really counts, spend 10 - 30 on one it’s probably not going to work.
Spend on the right product and at least the air won’t be an issue again.