Engine vented loop

[seadaddler]

My vented loop on my yanmar engine has water coming out the
hose into under my engine pan.
Can anyone tell me why and what is the need for the vented loop
Nick

 

[Claude L.-Auger]

My vented loop on my yanmar engine has water coming out the
hose into under my engine pan.
Can anyone tell me why and what is the need for the vented loop
Nick

Hi Nick. The vented loop is there to prevent water from siphoning back into the engine when there is no exhaust pressure. Assuming your exhaust elbow is in good shape, if you have water leaking from any part you have a blockage somewhere preventing the vented loop from doing its job. Shut of your water intake through hull, disconnect the hoses and check them. it could also be the vented loop itself. Some are plastic with a tiny metal spring inside the vent. Spring gets corroded and breaks, allowing water back in. Good luck

 

[Rick D]

Replaced mine

My vented loop on my yanmar engine has water coming out the
hose into under my engine pan.
Can anyone tell me why and what is the need for the vented loop
Nick

After some years of frustration and dribbles on one of my motor mounts, I replaced the factory unit with a Vetus. That was ten years ago; no problem since:
http://www.vetusmarine.com/store/p/335-Airvent-With-Valve.aspx

 

[Stu Jackson]

Discussed here:

 

[seadaddler]

Loop vent

It think mine has screws to take apart and clean and so will try that
or replace as mentioned.
Nick

 

[Bill Roosa]

Perhaps you should check the check valve at the top of the loop to make sure it it closing during operation. They tend to get salted up and leak. Pretty easy to fix too.

 

[newage1461]

I've had 2 boats with Yanmar engines and neither had a vented loop.

 

[Stu Jackson]

I've had 2 boats with Yanmar engines and neither had a vented loop.

newage,

That's quite possible.

With no intent to disparage your previous boats, AND more importantly for those who are unfamiliar with this subject, it would be helpful to point out that if the engine is below the waterline and is water cooled, then those installations should have them.

I urge those folks to read the link I provided earlier which is, IIRC, from GOB magazine and explains it all.

Just don't want anyone to misinterpret and say, "Heck, if he didn't have two, I don't need one, either."

 

[newage1461]

I'm unable to look at my setup for several months, but as memory serves the exhaust hose goes from the elbow directly under the fuel tank and out the exhaust port. The engine is I believe above the waterline. 1981 Hunter 30 .

 

[Claude L.-Auger]

It think mine has screws to take apart and clean and so will try that
or replace as mentioned.
Nick

Hi again Nick, as posted in my first post and as Bill said, you can perhaps fix the vent itself. Mine was broken so I went to a Vetus 6 or 7 years ago and have not had a problem since. For $60 it was one of the cheapest long term part change I ever did.

http://www.jamestowndistributors.com/userportal/show_product.do?pid=11754

 

[Bill Roosa]

Think we are talking about two different things here. the raw water feed needs a vented loop. Only raw water in that circuit. The exhaust also needs a vented loop but there is raw water and exhaust in it. I believe the OP was concerned with the raw water feed and not with the exhaust loop.

 

[Bill Roosa]

the raw water vented loop (usually) has a valve that has a "cap" that holds the valve parts together. The valve is a standard mushroom type and after taking the cap off you can clean it then reinstall. no need to even take off the hoses. should be part of everybody's (that has one of course) yearly maintenance tasks

 

[Stu Jackson]

Think we are talking about two different things here. the raw water feed needs a vented loop. Only raw water in that circuit. ...

Bill, new to me. Where would that VL be?

 

[seadaddler]

Vented loop

I am pretty sure my vented loop is a Vetus as in the Jamestown photo
will take the screws out and check it and clean if that is the problem.
Been busy at my house and getting ready for our drive up to NY for Xmas.
next week will check it out for sure.
And thank for all the help and everyone have a happy Xmas.
Nick

 

[Bill Roosa]

The raw water vented loop is between the raw water pump and heat exchanger. Mine is at the extream aft end of the engine compartment.
A vetus is a water lift muffler item in the exhaust loop. It pumps the raw water using exhaust pressure up and over the exhaust loop. It would not dump water into the engine sump. The exhaust loop is not really an anti-siphon loop. since it dumps immediately into the above the water line thru-hull it is just a high spot in the exhaust that keeps sea water from flowing backward into the engine from the thru-hull. No anti-siphon suction breaking one way valve in it so not much chance of it leaking.
The raw water loop does have a one way (into the hose) vacuum braking valve that can get salted up over time and leak raw water into the engine sump.

 

[seadaddler]

mixing elbo

My vented loop is vetus brand and one end is connected to the
mixing elbo.
My vented loop looks just like what Auger posted from Jamestown supplier
nick

 

[interpanama]

Vented Loop

I had exactly same problem with my H 376. I found it is an anti siphon device. Apparently if you shut down the engine in some circumstances water can back flow into the engine. Seeing as we are FWC Fresh Water Cooled as an engineer I didn't see this as much of a problem. I removed it completely four years ago and have not had any problems since.

Hope this helps

Alan