Yanmar 2GM20F

[Pete17844]

I need to change the coolant in our Yanmar 2GM20F. Would someone with the same model be willing to offer a step-by-step? The manual leaves a bit to be desired, such as the fact that more than the one drain shown in the manual appears to be present on the engine.

Many thanks.

 

[Steve Dion]

Pete:

I just faced this on our current boat. We have a different engine, but the same problem exists. One thing that is very important is to be sure that ALL of the old stuff is out of the system. This is only a problem if you are changing from the "green" stuff, like Prestone to the newer Long Life/extended life anti-freeze. If you do not get all of the old stuff out, the stuff will gel and you will have a mess.

We ended up having someone who know what the hell they are doing do our change out.

PS: Yanmar recommends use the newer stuff now.

 

[Paul8789]

I have changed the coolant in my 2GM20F and replaced it with the orange, long-life coolant. The job is not too difficult. There should be two drains on the starbord side engine block. There is another drain on the heat exchanger. The heat exchanger should have clear liquid, like lake water or sea water,and dosen't need to be drained unless you are winterizing for the season and are not planning on using the engine until spring. I have also run RV antifreeze, the pink stuff, thru the heat exchanger system, to prevent freezing. The enging block will contain the colored liquid, the coolant. The drains might have a plastic tube attached to help direct the coolant to a bucket or other container.
You should also have an overflow bottle that connects by a hose to the fill cap, like on a car radiator. This will also contain coolant. Be sure the system is not hot before opening the fill cap. Opening the fill cap will allow the coolant to flow from the block more freely once the drains are opened.
You may want to flush the engine several times to remove all of the old coolant. This can be done with fresh water. Run the engine several minutes to allow the water to circulate around the block. Again, let the system cool before opening the fill cap.
Once the water coming from the drains is clear, you are ready to install the new coolant. Be sure and top off the overflow bottle to the proper level. It is marked on the side of the bottle.
Good luck!!

 

[Don S/V ILLusion]

If you are going to replace the green with orange long-life silicate free coolant, there is another caution in addition tot he warning Steve mentioned -
Make sure you also thoroughly flush out the lines to/from the water heater core. These lines also have antifreeze in them and can be overlooked.

 

[Ken Palmer]

Water heater hoses

I seem to remember that when I performed the same task with the same engine, that I had to make sure that the engine coolant to and from the water heater was also drained. They then need to be "topped off" so as not to have air in the lines. I hope that I remember that correctly.

 

[Pete17844]

Thanks to all. My plan is to stick with the green (Prestone) for this winter. I have green in there currently which has lost some kick, shows +5 only on the test. I'm interested in winterizing and then will do a thorough flush in the spring to change to the long-life.

Am I correct to presume that running the RV (pink) through the water pump and out the exhaust takes care of the heat exchanger?

Thanks again all.

 

[Don S/V ILLusion]

Am I correct to presume that running the RV (pink) through the water pump and out the exhaust takes care of the heat exchanger?

Thanks again all.

Yes - don't forget the raw water strainer too if you have one.

 

[Coyote]

I have also run RV antifreeze, the pink stuff, thru the heat exchanger system, to prevent freezing.

hey Wyliejac:

What do we know about "FREEZING" down here on the Gulf Coast of FL????

good useful info on this post ---

"Coyote" - CLEARWATER

 

[Warren Milberg]

The below advice, from Mack Boring, is for the Yanmar 3GM30F, but is essentially the same procedure for the 2GM20F:

"Coolant Change – Yanmar 3GM30FC (Japan, circa 1999)Coolant Change – Yanmar
3GM30FC (Japan, circa 1999)

Background:
Yanmar accepts the following antifreeze applications in their products, present
and past models:
1. Ethylene glycol-Changed annually regardless of hours of operation.
2. Extended Life Antifreeze or Coolant (Meets or exceeds ASTM D3306 & D4985)
Changed every two years or 250 hours whichever comes first.
-Yanmar Ultralife YG30
-Dex-Cool Long Lfe Coolant
-Havoline Extended Life Antifreeze
Benefits of extended life coolants:
1. reduces hard scale build up
2. better heat transfer
3. no phosphate or silicate formation
4. long term corrosion protection for aluminum, bronze and cast iron
5. improved water pump life

Thomas J. Watts
Technical Support, Mack Boring & Parts Company
908-964-0700 ext. 286
tomw@mackboring.com

Equipment List:
0.5 gal Dexcool-type Extended Life Antifreeze (ex. Prestone 5yr/150000mi)
Or 1 gal of pre-mix version of above
Coolant system flush (must be safe for aluminum) (ex. Prestone Super
Flush)-Optional
Pliers
Funnel
Bucket or catch-basin
Water (Makeup water should be soft water or distilled water)

Instructions:
1/ On a cool engine, loosen the filler cap and drain old coolant into container.
On my engine, there are 3 drain points. Most volume came out of the block drain
fitting on the port side just aft of the oil filter. Approx. 16 oz came out of
the 2 drains on the heat exchanger, starboard side.

2/ After draining the engine, remove one of the hot water tank hoses from the
top front of the engine. Keep the 2 coolant drains on the engine open. Put on
the radiator cap and put your finger over the opening on the engine where the
hot water heater hose was connected. Clean off the hot water heater hose and
then blow on the hose and the hot water heater loop is emptied (about 1/2
gallon).

3/ Remove and clean the overflow tank. It pulls straight up off of its mounting
bracket.

4/ Close all drains and fill with water. Replace filler cap. Run engine until
thermostat opens and temperature stabilizes. Then shutdown and allow to cool.

5/ Drain (ie. Repeat step 1) Refill with coolant system flush chemical
(optional) plus water as required to fill. Run engine until thermostat opens.
Shutdown and allow to cool.

7/ Drain (ie. Repeat step 1) Refill with water to flush out the cleaning
chemical (ie. Repeat step 3). Do this 3 or 4 times until drained water is clean
and free from ethylene glycol (green) antifreeze.
Note: if you are staying with the EG antifreeze or did not use the flush
chemical, 1 or 2 water flushes should be sufficient.

8/ Drain for the last time. Refill with the 50/50 mix of Dexcool-type extended
life antifreeze. Fill overflow tank slightly above the "min" mark.

9/ Start engine, check for leaks and proper temperature. After shutdown, recheck
level in overflow tank."

PS: There are some owners who do not recommend the use of Dex-Cool, however, the Yanmar techs at Mack Boring stand behind it. See: http://www.imcool.com/articles/antifreeze-coolant/dexcool-macs2001.php