header/expansion tank beta 43

[dave mackie]

It looks like i have a remote steel header/expansion tank ( large screw cap on it instead of radiator cap ) hidden away above the deck on my NB , but i still have a radiator cap on engine .Is this normal as i would of thought the radiator cap on engine should be blanked off and refitted to the remote header/expansion tank that is fitted above deck . Any thoughts . Its a Beta 43 engine .

[Machpoint005]

Which one is the thermostat?

 

[dave mackie]

thermostat is in cylinder head as standard 

[Tony Brooks]

It depends how it has been piped but the "radiator cap" can have a seal under the cap or just a plain metal cap. If it has a rubber seal then the other tank cap must be vented. I that case i would expect the expansion tank to be connected to the engine by the small hose that is normally in the filler neck. If it is anywhere else then either the metal cap is a pressure cap as well or you are running unpressurised that is unlikely to be a problem until you get onto a large river or tidal waterway.

 

The radiator cap may be plain cap with no spring thing hanging down form the underside but with a seal. If so the metal cap will be a pressure cap or you are running unpressurised.

 

All dependant upon how the pipework is configured.

Edited November 22, 2021 by Tony Brooks

[matty40s]

This is quite a common installation for Beta's, the problems arise subsequently when someone comes along and replaces the unpressurised cap with a pressurised one and vice-versa.

[dave mackie]

Cheers for the info .  Would it be that the remote expansion tank which is above deck is that high away from engine because my calorifier is slightly higher than engine and the height of expansion tank would help stop air locks in calorifier coil.

[Iain_S]

3 hours ago, dave mackie said:

Cheers for the info .  Would it be that the remote expansion tank which is above deck is that high away from engine because my calorifier is slightly higher than engine and the height of expansion tank would help stop air locks in calorifier coil.

Would help, but main reason is to keep the heat exchanger full, especially if there is a large skin tank, and make it easier to check, unless, of course, it's hidden away!  

 

There are two methods of fitting which are found on Betas. The official one uses a tapping in the thermostat cover, and has a pressure cap on expansion tank and the heat exchanger. The other method is to use the overflow at the heat exchanger, in which case it should have a flat cap on the heat exchanger and a pressure cap on the expansion tank.

Edited November 23, 2021 by Iain_S

[Tony Brooks]

7 hours ago, Iain_S said:

The other method is to use the overflow at the heat exchanger, in which case it should have a flat cap on the heat exchanger and a pressure cap on the expansion tank.

 

Except there are pressure caps with a seal under the cap itself  and one of those will do the job along with  a vented cap on the tank. Without more info we don't know what the OP has so have to guess.

[Phoenix_V]

This is the standard Beta fit from their parts list. Plain cap on expansion tank which connects to tapping on thermostat housing. 13 psi standard pressure cap retained on heat exchanger. From memory I think they  use a repurposed Citroen expansion tank!

[Tony Brooks]

7 minutes ago, Phoenix_V said:

This is the standard Beta fit from their parts list. Plain cap on expansion tank which connects to tapping on thermostat housing. 13 psi standard pressure cap retained on heat exchanger. From memory I think they  use a repurposed Citroen expansion tank!

 

And the plastic cap on the bottle is almost contains a PRV and vacuum breaker valve, as per modern cars. Ideally the one on the manifold would have a higher pressure setting so any loss of coolant would be form the bottle and not the manifold cap.

[Tractor]

Or, is this two systems ‘engine’ witch will be pressurised, using the radiator cap; and the header tank is serving the boat heating, radiators?

[Cheshire cat]

My Beta 35 is similar to that diagram except the takeoff is from the engine header water jacket and there are two remote expansion tanks working in tandem.

 

The skin tank is so large that the volume of coolant expands by two litres between cold and hot. Once up to running temperature both containers are full but once moored up it all disappears back into the engine again.

[Tony Brooks]

4 minutes ago, Tractor said:

Or, is this two systems ‘engine’ witch will be pressurised, using the radiator cap; and the header tank is serving the boat heating, radiators?

 

No,  it is a modification of the engine cooling system to allow it to run pressurised with an expansion tank. In truth it is a bit of a bodge, be it an effective one, to overcome the problem of high coolant volumes in skin tans systems expanding when heated.

[Phoenix_V]

30 minutes ago, Tony Brooks said:

 

And the plastic cap on the bottle is almost contains a PRV and vacuum breaker valve, as per modern cars. Ideally the one on the manifold would have a higher pressure setting so any loss of coolant would be form the bottle and not the manifold cap.

I'm not on the boat so can't examine the tank cap but coolant overflow is definitely from the manifold cap

[Tony Brooks]

6 minutes ago, Phoenix_V said:

I'm not on the boat so can't examine the tank cap but coolant overflow is definitely from the manifold cap

 

Yes, many are. There is nothing wrong with this as long as it works as it should but many don't.  We are back to needing to know the details of individual systems.

[pearley]

1 hour ago, Phoenix_V said:

This is the standard Beta fit from their parts list. Plain cap on expansion tank which connects to tapping on thermostat housing. 13 psi standard pressure cap retained on heat exchanger. From memory I think they  use a repurposed Citroen expansion tank!

Definitely Citroen.

[dave mackie]

Thanks for all replies, the steel header tank I have has two outlet pipes at bottom of tank. I’m not at boat at moment but should be back at W/end so will take some pics ..cheers again👍

[Tony Brooks]

1 hour ago, dave mackie said:

Thanks for all replies, the steel header tank I have has two outlet pipes at bottom of tank. I’m not at boat at moment but should be back at W/end so will take some pics ..cheers again👍

 

In that case some of the circulating coolant probably passes through the tank and if the tank cap is not a pressure cap the engine is running unpressurised. I think the two pies are an aid to self bleeding. one from lower down on the system and one from high up.

 

As I said, running unpressurised is unlikely to cause any problems unless you run at high speed AND powers for long periods.