Pressure cap for a Yanmar 4JH4E

[Ian_Edwards]

I posted earlier on an overheating problem with my Yanmar Diesel.
Yanmar 4JH4E RUNNING HOT!

The high oil level turned out to be a silly mistake, it had simply been over filled, and doesn't appear to have anything to do with the overheating problem. I pumped some of the oil out, no water, no smell of diesel and the viscosity looked normal. It ran for the rest of the season without filling up or using any oil.
However, the overheating problem is still there, sort of.
When I check the header/expansion tank, it is at the full mark, and hasn't moved.
When I check the water level at the heat exchanger, under the pressure cap, there is air at the top of the heat exchanger. I takes around 100 to 200ml of water to fill it after several hours of motoring. As long as there is water in the heat exchanger the engine runs normally, at around 80C.
I've taken the small hose, next to the pressure cap off, and poked a small screwdriver through the pipe into the heat exchanger, and it's clear, I've blow back up the small hose to the expansion tank, and I can hear the bubbles in the tank. So, I know there's no blockage there.
I'm wondering why the antifreeze mixture in the expansion tank doesn’t run back into the heat exchanger, when the engine is cold, and when the pressure cap is off.
The engine is losing water slowly, but I’ve no idea were.
It could be via the heat exchanger, which was stripped, cleaned, and rebuilt 2 years ago, or the cylinder head gasket, or the calorifier, which has a heating coil in it, or could the pressure cap have anything to do with it?
What’s the best way to go about finding the leak?
To make matters more complicated, the boat is out of the water until next April.

 

[VicS]

I assume what you are calling the "header/expansion tank" is what is shown in the manual as the "coolant recovery tank"

When the system cools coolant in the recovery tank should be sucked back into the heat exchanger,
I suspect yours is sucking air in rather than sucking coolant back in

I would insect the cap on the heat exchanger. It must make an air tight seal on the top of the filler neck.
Are you sure it is the correct cap? If it is perhaps it is worn or defective in some way so that there is not an air tight seal on the filler neck

 

[penfold]

Writing rubbish, ignore me.

 

[Ian_Edwards]

I assume what you are calling the "header/expansion tank" is what is shown in the manual as the "coolant recovery tank" ..... yes that is correct.
The pressure cap is the original from 2007, so may well need replacing.
The pressure cap part number 129673-44130, as per the parts list I have for the 4JH4E, but can't find one.
The part number 129673-44131 seems to come up in the USA and Canada, but seems to be very expensive.
I find it hard to believe that it's not Stardard generic part, but I don't seem to be able t find it.
I don't know very much about pressure caps and their specification, can anyone help?

 

[mrangry]

My Yanmar 4jh2e also does this and also suspect the cap, but as yet not found a replacement so watching with interest.

 

[Ian_Edwards]

Hi,
I spent some time last night searching the net for problems with the filler cap on Yanmar 4JH4E's and simillar engines. I found a post on the sail boat owners forum, which points to a Yanmar Global Technical Bulitin for this problem GTB201004.
Antifreeze leak
It seems that the Filler Neck is not welded to the heat exchange, it is a form of compression fitting, presumably because the heat exchanger is alumimium, and the filler neck is some form of brass.
The filler neck is pressed into the heat exchanger and a copper sleve is pressed into the filler neck to expand it.
These photos are from the the SailBoat Owners website.





There's a link to the tech' file below..
I think that this is probably the the source of the leak, I'll have closer look next time I'm on the boat

 

[penfold]

I assume what you are calling the "header/expansion tank" is what is shown in the manual as the "coolant recovery tank" ..... yes that is correct.
The pressure cap is the original from 2007, so may well need replacing.
The pressure cap part number 129673-44130, as per the parts list I have for the 4JH4E, but can't find one.
The part number 129673-44131 seems to come up in the USA and Canada, but seems to be very expensive.
I find it hard to believe that it's not Stardard generic part, but I don't seem to be able t find it.
I don't know very much about pressure caps and their specification, can anyone help?

Given Yanmar are japanese perhaps the oddly sized radiator caps common on some japanese cars might be worth perusing? There are a few online specialists with decent websites, even ebay is worth a look although getting the search terms right can be a bear.

 

[Ian_Edwards]

Thanks, yes that's a thought, but as you say the car parts are unlikely to have a Yanmar part number, and I don't know how else to describe it, all I know is that it is 0.9bar release pressure.

 

[penfold]

Often all you have to go on is the pressure rating and the physical measurements, fortunately there are a few vendors who understand this and list these vital statistics.

 

[Bilgediver]

Vic mentioned that it was important to have the right caps fitted. Check what you have. The cap on the heat exchanger should be bi directional, IE it vents outward at a certain pressure and then under negative pressure lets the water flow back from the expansion tank. The cap on the expansion tank does not have to be bidirectional but may look similar. Have they been mixed up?

 

[VicS]

I assume what you are calling the "header/expansion tank" is what is shown in the manual as the "coolant recovery tank" ..... yes that is correct.
The pressure cap is the original from 2007, so may well need replacing.
The pressure cap part number 129673-44130, as per the parts list I have for the 4JH4E, but can't find one.
The part number 129673-44131 seems to come up in the USA and Canada, but seems to be very expensive.
I find it hard to believe that it's not Stardard generic part, but I don't seem to be able t find it.
I don't know very much about pressure caps and their specification, can anyone help?

This comes up on French Marine's website



Very expensive ?
Half the price of a Volvo Penta cap!

But I would not buy it until I was certain that the cap is the problem

.