appropriate PSI for coolant cap

[Tomm]

Hey

 

Getting a bit of liquid in engine compartment. Engine is Beta Marine. Wondered if water was escapeing from the coolant cap. Does anyone know what PSI would be appropriate for this engine? Its not too much liquid but wondered if this could be the problem.

[bowten]

Hey

 

Getting a bit of liquid in engine compartment. Engine is Beta Marine. Wondered if water was escapeing from the coolant cap. Does anyone know what PSI would be appropriate for this engine? Its not too much liquid but wondered if this could be the problem.

Have you overfilled the coolant.

[alan_fincher]

I don't specifically know for Beta, but usually the pressure settings on caps used in these applications are low - maybe in the 4 to 7 psi range, possibly a bit more, but not a lot more, generally.

 

Many engines connected to a large skin tank need there to be a surprisingly large amount of air in the header tank when the engine is cold, (with maybe half the header tank empty), otherwise as the engine teaches full temp expansion will always cause fluid loss.

 

If you are in that situation, and keep topping up, then unless you are using an antifreeze mix each time, you risk the antifreeze protection getting progressively reduced.

 

But sometimes it is the pressure cap not sealing properly - I have had this too......

[bowten]

Are you sure it is coming from the coolant cap and not the small overflow pipe just underneath the cap.

[Arthur Brown]

Slip a pipe onto the overflow outlet and see if, what and how much flows from the overflow rather than the cap seal.

 

While the header tank may have "top" and "Lower" levels marked you may need to run lower than these when cold to retain enough capacity for the large volume to expand as the temperature rises.

[bottle]

If it is a Beta Marine 43 or larger the pressure is 15 psi. or 95kPa

 

Reference:http://www.betamarine.co.uk/literature/spare%20parts%20listings/B43_to_B60_Spares_List.pdf large PDF file.

[Giggetty]

If it is a Beta Marine 43 or larger the pressure is 15 psi. or 95kPa

 

Reference:http://www.betamarine.co.uk/literature/spare%20parts%20listings/B43_to_B60_Spares_List.pdf large PDF file.

My 20 hp Bukh needs a 4lb pressure cap.

 

Advice for persistent overflow is to install an expansion tank. In this mode the header tank may be filled to the top. (q.v. www.cbsonline.co.uk).

[Giggetty]

My 20 hp Bukh needs a 4lb pressure cap.

 

Advice for persistent overflow is to install an expansion tank. In this mode the header tank may be filled to the top. (q.v. www.cbsonline.co.uk).

This has set me thinking. Can anyone see what is wrong with this circuit? My link

 

(use a magnifying glass in Gallery-haven't got the hang of this yet).

Edited February 27, 2013 by Giggetty

[churchward]

If it is a Beta Marine 43 or larger the pressure is 15 psi. or 95kPa

 

Reference:http://www.betamarine.co.uk/literature/spare%20parts%20listings/B43_to_B60_Spares_List.pdf large PDF file.

I am pretty sure it is the same PSi for all the Beta narrowboat range. ie 15 PSI it is certainly that on my B38/BV1505

[Tony Brooks]

I am pretty sure it is the same PSi for all the Beta narrowboat range. ie 15 PSI it is certainly that on my B38/BV1505

 

 

You may have problems form too low a pressure but as long as the hoses stay on and the water pump seal does not leak not from too high. The only exception I would make is anything with rubber endcaps on the manifold (BMCs), then I would be a bit cautious.

[churchward]

You may have problems form too low a pressure but as long as the hoses stay on and the water pump seal does not leak not from too high. The only exception I would make is anything with rubber endcaps on the manifold (BMCs), then I would be a bit cautious.

On the BMC with those horrible rubber boots I would expect it to be 4PSI or may be up to 7PSI but no more. They might balloon up more than they do normally and fail.

[Alanji]

Put a plastic tube on the overflow pipe, as Arthur Brown suggested, and put the other end in a bottle, with some antifreeze mixture in it. If engine overheats bottle fills - when cool draws water back into engine. No loss of antifreeze mixture and you can see at a glance that you do not need top-up.

Courtesy of RCR course earlier this month.

[jelunga]

Put a plastic tube on the overflow pipe, as Arthur Brown suggested, and put the other end in a bottle, with some antifreeze mixture in it. If engine overheats bottle fills - when cool draws water back into engine. No loss of antifreeze mixture and you can see at a glance that you do not need top-up.

Courtesy of RCR course earlier this month.

provided the cap is designed for return flow. Some were / are not.

[Tony Brooks]

provided the cap is designed for return flow. Some were / are not.

 

 

Most are not because they have a brass diaphragm rather than a rubber seal immediately under the cap. If you want to try it ask a motor factors for a cap off a Mk 1 Fiesta but it may only be a 6PSI cap.