Coolant Change Yanmar4JH4-HTE

[Metric Rider]

Went to do a coolant change for the first time since purchasing LiL Toot, our 2008 R25. I am having trouble locating the "coolant drain cocks" referred to in the Yanmar manual. Are there actual petcocks or is it just rubber hose connections that are to be removed? According to the diagrams in the manual it looks like 3 possible locations. Any help on this would be appreciated.

 

[Tom Zmon]

I just changed out my antifreeze on my 2008 R-25. There are Petcocks. I agree that they are well hidden. It was easier for me to just remove the rubber hose.

 

[Kaisardog]

having done this same maintenance on a 3JH4E recently, i sympathize with your problem of finding the drain plug. i found mine by pulling my service manual which had blowup drawings of the cooling system and showed the drain plug for the cooling system as a hex head bolt located very close to the coolant pump inlet to the cylinder block. it may have a small overflow hose attached to it.

depending how many hours you have on your engine (500+?) you may also want to consider pulling the heat exchanger and cleaning out the ht ex tubes while you are at it.

yanmar offers not just the little free 'owners' manual of 30 pages or so, but also a Service manual and Parts manual which any owner can buy from the Dealer. getting those manuals will help you to find out where all kinds of things are located. you can also try online boat diesel.com which is a for-pay website that has online editions of both the service manual and parts manuals for all engines once you pay your $25 a year. the forum also has a Q and A where you can ask a question and get a rapid answer from very well qualified fellow Yanmar owners and service people. For example i needed an answer about a turbocharger and i was pleased to see the king of Yanmar techs on the west coast personally reply to my inquiry and followup with some very valuable advice.

 

[doke01]

I have a 4JH3-DTE. There are 4 petcocks. You can use a small wrench to open them. The overflow/clear hoses go right into them, if you have them. There is one on the ports side aft, under the heat exchanger. One on the starboard side near the oil pressure sensor. One under the turbo, and a hidden one under hose that goes under the water pump on the front of the motor. Make sure they are tightened down when you are done but not over tight. I had one wiggle loose and start dumping antifreeze in the bilge. Luckily I caught it before any serious issues.

 

[Metric Rider]

The Yanmar manual states the coolant capacity as 7.2 L for the 4JH4-HTE. I presume that with the loop to heater that the total capacity would be a bit more. Does draining the coolant from the engine petcocks drain the lines from the heater loop or do you have to make a disconnection in the heater loop somewhere?

 

[Metric Rider]

Finally got around to draining the coolant after having found the 3 petcocks. Got around the specified quantity ( 7.2L) of used coolant drained and collected for disposal. I am doing this work while I am on the trailer. My question now is about refilling the system. I was able to pour about 3.8 L of newcoolant in the heat exchanger before it began to overflow and filled the appropriate amount in the overflow tank but the system needs 3 + L still to be added. I presume I cannot add it now until the thermostat opens as the engine heats up. Not sure the best way to add, is it to keep adding to the overflow tank or is there a way to add to the heat exchanger without getting scalded from the hot coolant? Any comments or suggestions appreciated!

 

[knotflying]

Always wait until cool and then add to the heat exchanger.

 

[doke01]

On the front of the engine, center top is a cover with a hose going to the right to connect to the heat exchanger with two bolts that, when removed, exposes the thermostat. Remove the cover and thermostat and fill the block with anti-freeze. Replace the thermostat and cover and then fill they heat exchanger. Make sure you pay attention to which way the thermostat was/is installed and be careful not to damage the thermostat gasket. If you damage/tear the gasket it will need to be replaced (I put it back together and look for leaks to determine if it needs replacing myself). Re-installing the thermostat incorrectly can cause overheating so make sure you install it the same way it came out. Since you already filled the heat exchanger you will need to drain it before adding anti-freeze to the the block or you will get a big mess when removing the thermostat.

Definitely DO NOT run the engine without antifreeze in the block. With no anti-freeze you will cause serious damage and the thermostat won't open anyway without anti-freeze in the block to trigger it.

Run the engine to full operating temperature and then shut it down. Once cool, check and refill as necessary. You may have to do this a couple of times to get any air bubbles out. When taking off the radiator cap the anti-freeze should be pretty much where you filled it to prior to running.

Put anti-freeze into the overflow tank but don't fill it to the top. I fill it just above the bottom line since you already know that the anti-freeze is full in the engine you will need space for expansion.

Check your anti-freeze level for the next several times you use the engine. Sometimes an air pocket can take quite a bit of time to work its way out.

 

[Metric Rider]

Thanks so much for your knowledgeable and thorough response!

 

[Metric Rider]

Further to refilling of coolant after draining. I spoke to a Yanmar authorized mechanic I know, and this is how he fills the coolant after draining: fill the heat exchanger with the engine off, it will take about half the specified quantity of 7.2L. Then he said to start the engine (while in the water) with the cap off and when the engine is warm the coolant will start to circulate as soon as the thermostat opens, then you add the balance of the coolant, then replace the cap. He says he has always done it this way even though Yanmar recommends filling the additional coolant via the overflow tank. Use your own judgment and knowledge for this, the above presented for info only.

 

[Lobo]

Thanks for this information!! It is very helpful.

Dave
LOBO