Persistent Coolant Leak Issue!

[Nodak7]

OK I am turning this one over the the brain trust to give me a clue as to what is happening. I keep losing coolant from around the coolant cap. Oddly it usually only drains the expansion bottle then quits. This has been a persistent problem for quite some time. No external coolant leaks on the engine. I have changed the coolant cap three times and it still does it. Anyone else experience this issue? Yanmar 4JHE 1800 Hrs

 

[Michael Davis]

Are you sure it’s the rad cap? Maybe the neck to heat exchanger joint?

 

[SycloneDriver]

Yanmar had a problem with some of the coolant necks. They leak between the neck and the exchanger. There is a fix from Yanmar, the neck is replaced using a special tool. There are other threads on this subject.

 

[Nodak7]

Yanmar had a problem with some of the coolant necks. They leak between the neck and the exchanger. There is a fix from Yanmar, the neck is replaced using a special tool. There are other threads on this subject.

I did a search on this but found nothing! BTW I am not having any overheating issues just this darn coolant lose. I will continue my search!

 

[clavius]

Here's a related thread...

Filler Neck Replacement on Yanmar YM-series Heat Exchanger?

Found a crack in the filler neck of our Yanmar 3YM30. I pulled the heat exchanger and pressurized it through the overflow tube per the shop manual and air bubbled out of the crack. I have a replacement filler neck and the sealing copper ring that has to be pressed inside the neck to force the...

forums.sailboatowners.com

 

[clavius]

Another related thread on another forum. On post #13 of that thread, the owner has the same engine as yours. He mentions there is a Yanmar service bulletin for replacing the filler neck.

Yanmar coolant filler neck loose - Cruisers & Sailing Forums

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

www.cruisersforum.com

 

[sailme88]

Are the new caps for the Yanmar engine that you have or a generic cap from NAPA? Universals require their specific cap. Because of the typical low clearance in the engine compartment, necessitates that the cap be a low profile.

 

[Nodak7]

Are the new caps for the Yanmar engine that you have or a generic cap from NAPA? Universals require their specific cap. Because of the typical low clearance in the engine compartment, necessitates that the cap be a low profile.

No they have been OEM caps purchased from Yanmar

 

[Nodak7]

I am thinking that indeed a leak at the filler neck is my problem. After doing some research it looks like the filler neck is "pressed" on and not bolted. I did find one "fix" using High Temp Liquid Gasket. Other than removing the existing one (which could get ugly) and pressing on a new one (which without the proper tools could get ugly as well) this looks like the best viable solution.

 

[ice breaker]

Thanks for the question. Now I understand why I always have a little pink stuff under the engine after a long winter lay up. During the summer all is tight. Must be the cold cycle shrinking the fittings.

 

[Michael Davis]

I once broke the neck to rad. joint on an old Toyota I had. A quick and dirty fix was to clean the area with sandpaper and silicone it back together. Was still good when I sold the car two years later.

 

[murrayabbott]

I have the same problem. It is a common problem. I went to Yanmar and they told me to move the expansion bottle. If the bottle is mounted above the valve cover on the engine will you have that leak. I moved It lower and the leak stopped.

 

[NYSail]

I have a 4JH4E 2005 with the same problem. I replaced the cap when I first bought boat and have noticed fluid.... I suspected the cap and bought a new one..... same results so I started to think it was the fill neck. Another person told me that they used jb weld around seam with neck and engine and it fixed their problem so I cleaned and applied. No luck..... however I confirmed it was the cap.... I saw it dripping. I also read about the reserve tank is not to be higher than 11 inches above. Mine was 12 so I lowered to about 8 and it slowed it dramatically. But still a few drips..... I am thinking to lower a couple more inches and see what happens. I really want to avoid replacing the neck.... sounds like a pain ( in the neck of course). Wonder if we could replace with a bolt on style..... they are much more reliable and solid.

Will be following.

Greg
2005 yanmar 4JH4E

 

[Rick486]

I have a 4JH4E 2005 with the same problem. I replaced the cap when I first bought boat and have noticed fluid.... I suspected the cap and bought a new one..... same results so I started to think it was the fill neck. Another person told me that they used jb weld around seam with neck and engine and it fixed their problem so I cleaned and applied. No luck..... however I confirmed it was the cap.... I saw it dripping. I also read about the reserve tank is not to be higher than 11 inches above. Mine was 12 so I lowered to about 8 and it slowed it dramatically. But still a few drips..... I am thinking to lower a couple more inches and see what happens. I really want to avoid replacing the neck.... sounds like a pain ( in the neck of course). Wonder if we could replace with a bolt on style..... they are much more reliable and solid.

Will be following.

Greg
2005 yanmar 4JH4E

point of information. On our 4JH4E the plastic reserve tank is much lower. The line from the top of the surge tank to the cap is essentially level.

 

[NYSail]

point of information. On our 4JH4E the plastic reserve tank is much lower. The line from the top of the surge tank to the cap is essentially level.

Yep.... I am going to lower as much as possible this weekend and see results. Thanks!

 

[Valerio]

i have same boat and same engine and the bottle is almost 10 inch above, yet not losing coolant in the cap.
Nodak7 all my hoses now are leaking (2004 boat)with 1200 hours, did you replace all your hoses?
If your fresh water system is partially clogged somewere you have some build up in pressure and the cap is made to loose pressure there. Have you ever cleaned you cooling system (both fresh and saltwater)?