Antifreeze leak

[murrayabbott]

I have been chasing a leak for in the engine for some time now and I think that I found it.

Antifreeze coolant seems to be leaking from the coolant pressure cap on top of the engine It is not antifreeze from the engine but from the recovery tank at/in the coolant pressure cap. When I look at the cap it looks in good condition.

Someone just mentioned that they thought that the recovery tank is mounted too high! They suggested that a correct install has the recovery tank lower than the coolant pressure cap.

The engine is a Yanmar 4jh4-te

Has anyone had a similar experience. How are recovery tanks installed on similar engines? The boat came like this new from Hunter. Here is a picture.

 

[stuartsw]

My mechanic wants me to move the recovery tank on my H36 below the level of the coolant pressure top. At ten years, I am also dealing with slow leaks. I am consulting a mechanic about changing out the entire set of coolant hoses and hose clamps, as well as replacing the gaskets in the thermostat.

 

[SycloneDriver]

There should be two rubber gaskets on the cap. One is for the pressure release and the other seals the outlet to the recovery tank. There are several styles of cap (vented & non vented come to mind). Also many different pressures but I sure you know that.

If the recovery tank is mounted above the cap and the outer gasket is missing or cracked you will have a slow leak.

Tip. Sometimes I find radiator caps that are very difficult to remove. If that cap has a gasket for a recover tank, but no tank is present, I remove the gasket.

 

[SycloneDriver]

Nice engine, 4 valves per cylinder turbo diesel. I just love turbos.
External voltage regulator as well. Your serious about your boating.

 

[uncledom]

Be wary of the hose clamps. I have had two that have rotted through and caused a slow leak. Both were back under the exhaust elbow and were a bit hard to see. I would suggest only AWAB hose clamps as replacements any time you remove a hose or a clamp looks suspect.

 

[Rich Stidger]

I find that you can't tell by looking if a coolant cap is bad. I had antifreeze disappear from my coolant tank with no obvious leaks. I finally replaced the cap and the antifreeze no longer disappears. So my original cap was apparently allowing antifreeze to vent as vapor and disappear. But the old cap looks good with no obvious defect.

 

[murrayabbott]

Thanks for the responses. I will lower the tank and change the cap.

 

[TFlight]

I chased that elusive leak for about 2 years. I tried the previous suggestions and some. It turns out when Yanmar produced the heat exchanger they press-fit the filler neck, Not welded or molded as one piece but pressed the filler neck into the heat exchanger.
there is a Global Technical Bulletin out for this repair GTB201004. I have the Yanmar 4jh4e and from what I can see they look the same. I will try and attach the Global Tech Bulletin but if it doesn't come through on my mobile app or you have further questions you can PM me.

 

[TFlight]

Here is the Global Technical Bulletin GBT 2010004 dated Apr 14, 2010