Volvo D2-55

[peterbotto]

I have this engine fitted to my Bavaria. At the rear of the engine is in inverted U pipe rising some 18ins above and behind the engine. At the top of this pipe is fitted a Vetus Vacuum valve with a small (third pipe) attached which is lead down to the bilge.
What is the function of this apparatus and why does the small 3rd pipe lead back to the bilge?
Many thanks

 

[hornblower]

I have also just acquired this engine on my new boat that is abroad - I shall check out the back of the engine for these pipes and see if I have the same arrangement.

 

[johnalison]

It's to stop the boat sinking!!

If a leak develops around the engine or pump it will break the syphon and save you oodles of pounds. It may need regular (annual) servicing unless it is a no-maintenance model.

Normally no water drains into the bilge, but this is not an adequate check and the diaphragm should be regularly replaced where present.

 

[branko]

This is breathing small valve for automatic emptying siphon tube. This valve commonly make problems with leaking and water inside motor compartment is 99% from this valve.
Most of Bavaria owners change this small tube with longer one and connect it in plastic container in-front down of the motor ( this small containers you have in every drugstore). Than every 2 or 3 days you can empty this container and motor compartment will be dry.
Some people connect small tube directly outside.

 

[Gypsy]

I have the same engine but the vacuum valve is from Volvo (I think). The 3rd pipe is for the air to break the vacuum when the pressure is off when the engine is stopped to ensure the water does not run back into the cylinder head. The reason it is taken to the bilge is that it is not uncommon for this valve to leak or weep and so the water is directed to the bilge.
It is a pain to have water dribbling into the bilge so it is common practice to put a collector such as a used mineral water bottle and empty it every so often BUT be sure not to allow the water to build up to block the hose coming from the valve as it may stop the valve opening and/or suck water back up and therefore defeat the purpose of the valve with very expensive consequences if water gets into the cylinders.

On my boat there was so much dripping I found a way to re-direct the hose to a basin hull outlet in the aft head but again you have to ensure that when the engine stops and the valve opens that it sucks back air, not water. This can be done by ensuring an air break is in the path. I was also advised by a couple of mechanics that this line could be safely fed back into the exhaust water lock but I found it did not quickly allow the air back through the valve so discarded that and I don't recommend that.
Ray