Yanmar coolant drain plug leaking

[Scott B]

Yanmar 3YM30. The coolant drain plug that is on the hose leading from the heat exchanger is leaking. ( not the drain plug on the side of the block) It is a round type of plug held on with a crimp on hose clamp. How do you open this to drain the coolant from the heat exchanger and how do I get it to stop leaking.

 

[Ed Schenck]

Yanmar 3YM coolant.

Hi Scott, I have the same problem/question. Maybe a call to Mack Boring will shed some light. I wonder if it is related to this item from the "Cruisers Forum":
"These early (2004/2005) engines have a 38-tube heat exchanger, and some very early engines were reportedly also fitted with a smaller capacity raw water pump than is now used. The fix is to replace the original 38-tube heat exchanger core with a new 63-tube one, and change the water pump if necessary.

If you have a Yanmar 3YM30 with an engine serial number under 6,000, I suggest you phone EP Barrus and ask if your engine is affected. I am not sure of the exact number of the last of the faulty batch, but Barrus knows. Don't rely on your Yanmar dealer having just serviced the engine to know about this!"

Barrus is a UK supplier. Change that to Mack Boring. I don't know my serial # but I think it is later than the aforementioned 6000.

 

[Scott B]

I have a file and forum bookmarks a mile thick on the 3YM30 overheating problem as mine started overheating the first season we had it. I eventually convinced Yanmar US to have the heat exchanger replaced under warranty even tho it was technically beyond the warranty period.

I don't think it would be related as this plug is in the middle of the hose leading to/from the exchanger and is not on the exchanger itself.

 

[Gordon Taylor]

Hi Scott,

Would be great to have a picture of the plug. Our Hunter 38 has a black plastic fitting on, if I can remember correctly, the coolant hose to the water heater. Mystified me for a while...but the black plastic cap unscrews and you can use a regular garden hose to flush the system. I cut a short section of hose and used with a funnel to flush and then refill with Dexcool.

 

[Scott B]

Gordon, I meant to get a pic last weekend but forgot while doing the rest of the winterizing. We were hauled out yesterday, and this weekend will be engine and tarps. I'll try to post a pic on Sat. am and hopefully have enough time to fix etc. before buttoning her up.

I know the cap you are talking about. This hose goes from the heat exchanger, across the front of the engine, and I believe to the thermostat. There is a drop down loop just out from the heat exch. with this plug. You wouldn't notice it unless you specifically look for it.

 

[Scott B]

Try this