Yanmar coolant filler neck loose

[Ocean Sky]

I have recently bought my very first boat..my friend tried to remove the coolant filler cap and twisted it without pushing down at the same time...2007 Yanmar 3JH4E.

Now there is a small gap all around the bottom of the filler neck where it fits on to the top of the heat exchanger .i am not too sure if this is just because the sealant has been broken or if there is an actual crack in the neck.when i run the engine there is hardly any water loss at all.

Would it be ok to just clean off the old sealant and simply seal it up again without dismantling the heat exchanger?

I have discovered on a 2005 manual on line that the neck is a separate part number which is attached on to the heat exchanger with sealant...but current Yanmar manuals no longer show this as an available part.

Any advice would be most appreciated,thanks!

[Bruce Beard]

Yanmar could not get that design to seal on out 2005 3JH4E for the entire time it was under warranty and they tried.
The neck is swaged into place at the factory and it always leaked from the time it was new. I ended up using a bolted flange type of gooseneck from an older Yanmar design. I removed the manifold, had it machined to accept the older flange and reinstalled. We never saw so much as a drop of coolant leak from there again.
Just sayin...
Bruce

[Ocean Sky]

Hi Bruce

Thanks for the information,hmmm looks like quite a big job, it wasn't leaking before my friend twisted it ,do you think it might be worth just trying to seal it again?

[Jacko]

Hey this is not a big deal just buy some epoxy putty ( available everywhere in a tube ) cut a bit off knead it together and seal the joint. This stuff will even set under water just make a small ridge around the neck and it will strengthen the joint. Wet your fingers to get a nice smooth finish. Good luck

[Ocean Sky]

Originally Posted by Jacko

Hey this is not a big deal just buy some epoxy putty ( available everywhere in a tube ) cut a bit off knead it together and seal the joint. This stuff will even set under water just make a small ridge around the neck and it will strengthen the joint. Wet your fingers to get a nice smooth finish. Good luck

Hi Jacko

Thanks for your input, will these products also withstand the high temperatures of the engine?

[Bruce Beard]

Originally Posted by Ocean Sky

Hi Jacko

Thanks for your input, will these products also withstand the high temperatures of the engine?

No they will not!
The filler neck is designed to be a kind of swage fit. There is a small copper ring inside the neck that is slightly larger than the thickness of the hole with the neck in it. There is a tool for tapping it in place but you can use a socket of the correct diameter too. If you want any chance at getting it back in place without a leak under pressure, use a new neck and a new swage. No sealant...
I found that no matter what Yanmar did, including various sealers, it leaked.
My fix was about $50 in total for a machine shop to drill and tap the 4 holes. You could easily do it yourself if you have a steady hand but I was tired of antifreeze running down and smoking on the hot alternator so I just had the machine do it on a milling machine...it was perfect!
We came all the way back from Bermuda smelling that awful hot smoky antifreeze smell...I never want to smell it again!
Bruce

[Ocean Sky]

Originally Posted by Bruce Beard

No they will not!
The filler neck is designed to be a kind of swage fit. There is a small copper ring inside the neck that is slightly larger than the thickness of the hole with the neck in it. There is a tool for tapping it in place but you can use a socket of the correct diameter too. If you want any chance at getting it back in place without a leak under pressure, use a new neck and a new swage. No sealant...
I found that no matter what Yanmar did, including various sealers, it leaked.
My fix was about $50 in total for a machine shop to drill and tap the 4 holes. You could easily do it yourself if you have a steady hand but I was tired of antifreeze running down and smoking on the hot alternator so I just had the machine do it on a milling machine...it was perfect!
We came all the way back from Bermuda smelling that awful hot smoky antifreeze smell...I never want to smell it again!
Bruce

Hi Bruce

Thanks for that information. i talked to the local yard but they say that filler neck part with the copper tube is no longer available ..so i will try the epoxy first .They want to take it off and weld it up ,but that is not how it was designed i think.

Someone has recommended JB Weld,or something similar that can withstand high temps,the pressure is only around 20 psi according to Yanmar.

Anyone had any success with these metal epoxy products?

[Ocean Sky]

Originally Posted by Ocean Sky

Hi Bruce

Thanks for that information. i talked to the local yard but they say that filler neck part with the copper tube is no longer available ..so i will try the epoxy first .They want to take it off and weld it up ,but that is not how it was designed i think.

Someone has recommended JB Weld,or something similar that can withstand high temps,the pressure is only around 20 psi according to Yanmar.

Anyone had any success with these metal epoxy products?

This is a pic ,the whole filler neck can rotate together with the cap about 2 inches left or right. it does not have hardly any leak at all so far.

[Bruce Beard]

It will leak, give it time.
We no longer own the boat with that Yanmar but I found this picture online of the part I retrofitted to our engine to permanently repair the problem. Any older Yanmar used this design and they are available if you look around.
All it takes is a gasket and 4 holes drilled and tapped for a forever repair...
Good luck!
Bruce

[Wanderlust]

Automotive shops have radiator repair sealant. I used that for a successful repiair in a previous boat, in a much more hostile situation.

The water inlet into the exhaust elbow snapped off. I positioned the broken water tube in place and pushed putty all around it. It was only intended to be temporary but it lasted a couple of years before leaking again.

[belizesailor]

Originally Posted by Bruce Beard

No they will not!
...

Depends on the product of course, just use the right one.

For example, many years ago I had a similar problem on a Volvo engine. Temporariy fixed it with JB Weld. Worked so well, I never changed. Many years later, its still not leaking.

[Ocean Sky]

I just picked up some JB Weld at Ace its good for 500f (260c),they didn't have the extreme heat one which is 900f in stock. So will give it a try .

i don't know the max temps experienced in these yanmar diesels?

Thanks for all the input guys!

[TFlight]

Originally Posted by Ocean Sky

I just picked up some JB Weld at Ace its good for 500f (260c),they didn't have the extreme heat one which is 900f in stock. So will give it a try .

i don't know the max temps experienced in these yanmar diesels?

Thanks for all the input guys!

I own a 2007 Yanmar 4JH4E with the same small annoying coolant leak around the base of the pressed in filler neck. Yanmar sent me a copy of a Tech Bulletin for replacing the filler neck. see attached.

I was wondering if the sealant around the Filler-Neck worked for you?
I'd like to try that first and if it doesn't work I'll replace the filler neck as per the Yanmar Tech Bulletin or replace with a flange type filler neck.

Also in regards to the earlier post showing the bolt on filler neck with the flange from an older engine, any idea what engine, year, or model that came off of?

Thanks,
TFlight

[Ocean Sky]

Originally Posted by TFlight

I own a 2007 Yanmar 4JH4E with the same small annoying coolant leak around the base of the pressed in filler neck. Yanmar sent me a copy of a Tech Bulletin for replacing the filler neck. see attached.

I was wondering if the sealant around the Filler-Neck worked for you?
I'd like to try that first and if it doesn't work I'll replace the filler neck as per the Yanmar Tech Bulletin or replace with a flange type filler neck.

Also in regards to the earlier post showing the bolt on filler neck with the flange from an older engine, any idea what engine, year, or model that came off of?

Thanks,
TFlight

Thanks for the Yanmar link .

i will be doing the JB bit early next week, will let you know how it goes.

[a64pilot]

Originally Posted by Ocean Sky

i don't know the max temps experienced in these yanmar diesels?

Thanks for all the input guys!

At the radiator cap neck, I would expect you would never, ever see more than 220F or so, and that would be when she was overheating, normally about 180F ?