Changing Coolant Yanmar 6LYA-STP

Mystery.... I'm changing the coolant in my Yanmar 6LYA-STP 370HP main engine, and I have only getting 3.5 gal of coolant when I drain the system. I flushed the system, and still only get 3.5 gal output. I ran the engine at 2000 rpm in the ICW (not at the dock) and the temp gauge didn't reach 175 degrees. Still only 3.5 gal output. The owner's manual says the coolant system holds 5.28 gal of coolant. I don't want to add 3.5 gal of new coolant and have that mix with 2 gal of old coolant. Any suggestions about completely draining the full 5.28 gal of coolant?

Changing Collant in Yanmar 6LYA-STP

3 places it can hide...low points in the block, coolers/heat exchangers and attached appliances like a water heater.

If you follow all the hoses and blow them out...then it's just a matter of finding the lowest point on the block to drain from and hope that gets it all. Call a Yanmar dealer or mechanic...they usually will tell you where to drain from.

If the system has a loop to the hot water heater the remaining 1.8 gal of fluid could be in the lines.

SteveH

Thanks Steve... the water heater isn't connected to the main engine.. I see where that can be done, but not on this engine/water heater... and I'm not seeing any other hoses to trace down... the drain i'm using is on the port side under the fresh water and above the starter motor.. I may have to trust the Yanmar mechanic on this one...

Thanks,

Are you extracting the coolant from the small valve/drain on the side of the block? That should be the best place for the lowest point on the engine but as talked about above coolant can collect in many places. I'm inclined to use an oil extractor and plumb it to the block drain valve and disconnect several hoses to drain water in low places in the hoses. Not much else can be done and I don't consider it an issue if I only get 80% of my coolant out and the 20% remains. Use the Long Life coolant (especially if you have aluminum engine parts in contact w the coolant) and I'll bet you do w a Yanmar. Change the coolant often (yearly) and I think your coolant will be in excellent condition.

manyboats said:

Are you extracting the coolant from the small valve/drain on the side of the block? That should be the best place for the lowest point on the engine but as talked about above coolant can collect in many places. I'm inclined to use an oil extractor and plumb it to the block drain valve and disconnect several hoses to drain water in low places in the hoses. Not much else can be done and I don't consider it an issue if I only get 80% of my coolant out and the 20% remains. Use the Long Life coolant (especially if you have aluminum engine parts in contact w the coolant) and I'll bet you do w a Yanmar. Change the coolant often (yearly) and I think your coolant will be in excellent condition.

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ANTIFREEZE HAVOLINE RED is what was put in at the Mainship plant. This is according to my boats Build Work Order for my hull which I have. I have the same engine a 6LYA -STP as Earl.

Earl: Based on an email query from Vinny, I went out and looked at the manuals and my 6LY engine this afternoon. The Operations Manual talks about draining the glycol coolant and gives diagrams noting the locations of the drain valves. There are two, port and starboard.


The port one is on the bottom of the heat exchanger just forward of the large vertical hose. Don’t confuse it with one just aft. That one is seawater.


The starboard one is on the bottom aft of the lube oil cooler sticking out to starboard. I don’t know why it is part of that cooler since it is seawater cooled. Maybe it is just part of the casting that bolts to the block and mates up with the coolant gallery. In any case I unscrewed the valve and nothing came out. Maybe it was plugged up inside and a wire pushed up inside would open it. I will investigate when I get around to changing the coolant, maybe this summer. It is 45 degrees outside now.


I suspect you will have to drain the starboard one which looks like it is lower to get most of the coolant out.


Good luck.

David

David... thanks to the Yanmar service center in Cocoa (Brian) there is another drain on the starboard side just aft of the lube oil cooler. It's a different type of drain - it sticks out at about a 50 degree angle, and I drained another 1.5 gal from that drain. I refilled 5 gal plus a little so I'm confident I drained almost all the old coolant before adding the new stuff...

thanks David....

djmarchand said:

The Operations Manual talks about draining the glycol coolant and gives diagrams noting the locations of the drain valves. There are two, port and starboard.

The port one is on the bottom of the heat exchanger just forward of the large vertical hose. Don’t confuse it with one just aft. That one is seawater.

Click to expand...

Thanks!

Feel like schmuck, but I was confused how I got more 'coolant' out of our 4JH2-UTE than went back in. Turns out I drained all three instead of just the two coolant petcocks.

Thanks again...one less mystery to resolve