Sound of Air Escaping

[t.mcbride]

I have just purchased a boat with a nearly new Yanmar 3J-4E diesel (less than 250 hours). There were a couple of times during our first cruise that we heard what sound like air escaping from a pressurized vessel. Not unlike the sound you hear when the air escapes from the brakes on a large truck. I would say the sound lasted for 3 to 5 seconds.

Any sugestions what this is? Is it the sign of something bad about to happen?

Thanks.

[Chief Engineer]

"scratching my head:"

When did you hear the sound.

Where were you when you heard it.

What were you doing when you heard it.

And Can you account for your wherabouts on the day it happened?

[Ex-Calif]

This may sound like a smart aleck question but the engine was running, right?

Bilge pump cavitating? More of a sucking sound?

[Alan Wheeler]

Yeah like, we have to know at least what colour the string is to give an indication of how long it is :-)

[Lancerbye]

What else have you got in that boat? Like I have a compressor for the air horn. If the pressure switch were to fail the high pressure release would dump the excess pressure. If you have a hotwater tank with a high pressure relief which is being heated by your engine it might dump if there is no place for the pressure to go. There are other possible senerios depending on what other systems you have on your boat.

[Boracay]

The only source of pressurised air on a marine diesel that I can think of is the exhaust.

Particularly if there is a bit of back pressure.

[Zanshin]

Air getting sucked into the fuel tank?

[speciald@ocens.]

Did you hear it when the engine was turned off? It would then be the anti-syphon vavle venting.

[MarkJ]

Your heads manual, electric or those vacume thingos?

[DWT]

A turtle next to the boat snorkling for air?

Hey! It happens all the time to me.

David
69Morgan30'
CarolAnn

[Whimsical]

Originally Posted by t.mcbride

There were a couple of times during our first cruise that we heard what sound like air escaping from a pressurized vessel. I would say the sound lasted for 3 to 5 seconds.
Thanks.

I have the same problem and my 5yo makes me excuse my self everytime it happens

Mike

[Wotname]

Mike takes the prize

[Lancerbye]

Originally Posted by Whimsical

I have the same problem and my 5yo makes me excuse my self everytime it happens

Mike

Mike you beat me to it or rather had a better way of saying what I was thinking.

[t.mcbride]

Thanks for all of the legitimate suggestions.

I think the most plausible answer is the water heater. I will check it next time we run under power for a few hours.

The sound always occured while at cruising speed after a good long run. We have no air horn and there are no large turtles in our area. We can't hear the bilge pump from the cockpit, when the engine is running and the head is manual.

Tony