I have a Hunter 29.5 with a Yanmar 2Gm engine with heat exchanger and antifreeze/coolant on one side. There are a couple of lines that run forward to the hot water tank . How often should this fluid be changed? What is the easiest way to drain it? I have a petcock installed in the line coming off of what I think is the thermostat housing on the top front of the engine which I am assuming could be opened to allow air in while draining the system, but I'm not sure where the best place is to drain it from, at the hot water tank?
Yanmar coolant fluid change
- Thread starter timangiel
- Start date
With regard to frequency of coolant change; I had a pump impeller fail after three years of service. Since then I always replace the impellers every two years. Since you must drain the coolant to change the impellers that is a good time to replace the coolant.
There is no need to change or access the coolant side in order to change an impeller. The two circuits, raw water and engine coolant are isolated by the heat exchanger.
Some of the long lasting stuff is claimed to be good for 5 years.. 3-5 years with that stuff is probably fine. Best to drain at the engine then flush with fresh water only (run until it reaches temperature) drain that fully then install coolant at the minimum temperature dilution.. The spigot is probably to bleed air after refilling with coolant.. In your part of the world, you'd want to test the anti freeze before laying up for winter! The wooly boogers are forecasting a cold winter! Your engine does not need a coolant drain to change the sea water impeller.
With many Yanmars there is a drain spigot with a clear hose on it. You can open the radiator cap and then drain off the coolant. If you want to flush it do as Kloudie mentioned above. I use distilled water for flushing unless it is really dirty and then I use Rydlyme. You then drain it again, flush with distilled, drain and finally refill with AF.
Be aware NOT to mix AF types unless it says safe for all makes. If you don't know what was in there before it is best to drain > fill with distilled > run to temp > drain > fill with distilled > run to temp > drain & finally fill with new AF. Once full be sure the system is well bled and there is no trapped air.
Be aware NOT to mix AF types unless it says safe for all makes. If you don't know what was in there before it is best to drain > fill with distilled > run to temp > drain > fill with distilled > run to temp > drain & finally fill with new AF. Once full be sure the system is well bled and there is no trapped air.
Best to read the owners' manual to see Yanmar's recommended change interval. Mine says every year or a certain number of hours. I change mine every other Spring.
After draining, refill the AF with the radiator cap off until the engine reaches full operating temperature. Add more AF as needed. May need to "burp" the system by removing thermostat.
The engine is a 2GMF. F denotes the type of cooling system you have. I have the same engine. There are two drain petcocks both on the starboard side. I *think* one of on the heat exchanger and the other on the engine block. Just my $0.02 but I wouldn't bother fussing with trying to get every last drop of coolant out of the system. If you replace 95% of the coolant, engine will be protected from freezing for the Winter.
It's extremely easy to change the coolant. Once you've drained the coolant, it's a good idea to change anything else that's old since it's super easy to do at that point. I recently changed all my hoses (they were all original) as well as the thermostat, cleaned the heat exchanger, and replaced several gaskets and o-rings. Working on these engines is a breeze! The hardest part was figuring out the correct part numbers and waiting on parts. I spent about $300 in parts when all was said and done to do a decent overhaul of the cooling system.
On the 2GM20F there are two small hoses on the side of the engine that drain the coolant. I drain those into empty water bottles, then dump them into an empty 1 gallon milk jug for disposal. Next, I filled up with distilled water and ran the engine for 15 minutes, then flushed it out. I repeated this process of flushing out several times. If you're needing it, you could plug the outlets for the water heater hoses, and take the time to replace those two hoses. I didn't do this, and I ended up needing to drain the coolant again not long after I did the flushing.
Then fill up the top with coolant. When you start the engine, you'll want to loosen each hose clamp and squeeze the hose a bit until coolant runs out to confirm that you've worked out all the air trapped in the system. It's a similar process to bleeding the fuel, you'll definitely want to bleed the coolant at each hose. My engine started to overheat when I first changed coolant because I had trapped air in the hoses. For the first couple minutes after starting the engine, keep topping off the system, then replace the radiator cap, and that's when you start to crack open hose clamps burb the air out of the system.
The biggest problem seems to be trapped air in the system. Another tool you'll want is an IR thermometer. As the engine is running, you aim the IR gun at various parts of the coolant system and engine, and note the temperatures. I run around 165-180 for different components of the coolant system and engine.
On the 2GM20F there are two small hoses on the side of the engine that drain the coolant. I drain those into empty water bottles, then dump them into an empty 1 gallon milk jug for disposal. Next, I filled up with distilled water and ran the engine for 15 minutes, then flushed it out. I repeated this process of flushing out several times. If you're needing it, you could plug the outlets for the water heater hoses, and take the time to replace those two hoses. I didn't do this, and I ended up needing to drain the coolant again not long after I did the flushing.
Then fill up the top with coolant. When you start the engine, you'll want to loosen each hose clamp and squeeze the hose a bit until coolant runs out to confirm that you've worked out all the air trapped in the system. It's a similar process to bleeding the fuel, you'll definitely want to bleed the coolant at each hose. My engine started to overheat when I first changed coolant because I had trapped air in the hoses. For the first couple minutes after starting the engine, keep topping off the system, then replace the radiator cap, and that's when you start to crack open hose clamps burb the air out of the system.
The biggest problem seems to be trapped air in the system. Another tool you'll want is an IR thermometer. As the engine is running, you aim the IR gun at various parts of the coolant system and engine, and note the temperatures. I run around 165-180 for different components of the coolant system and engine.
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I found it quite a pain to fully flush the years of crud in my system (suspect POs never changed coolant). I ended up writing myself instruction for when I do it again. Flushing and cleaning all the way to the water heater (with inaccessible hoses) was the big challenge. This is what I wrote up (3GM30F):
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)
· Air Mattress pump
· Temperature gun
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 pump air through the hose with an air mattress pump until the hot water heater loop is emptied (about 1/2 gallon) through the open engine drains.
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 (check with temperature gun). 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.
6. 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.
7. 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.
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)
· Air Mattress pump
· Temperature gun
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 pump air through the hose with an air mattress pump until the hot water heater loop is emptied (about 1/2 gallon) through the open engine drains.
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 (check with temperature gun). 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.
6. 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.
7. 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.
1. water heater lasts 8-10 years ($300-$700+)
2. coolant hoses last about 4 years (~$300? to replace all coolant system parts)
I think it's best to get on a cycle where you replace water heater, coolant, and coolant hoses every 8 years, and then between this cycle you replace all coolant hoses each 4 years. Each time replace coolant. It's much better to go with preventative maintenance than to wait until a hose bursts and you destroy your engine or get stranded.
2. coolant hoses last about 4 years (~$300? to replace all coolant system parts)
I think it's best to get on a cycle where you replace water heater, coolant, and coolant hoses every 8 years, and then between this cycle you replace all coolant hoses each 4 years. Each time replace coolant. It's much better to go with preventative maintenance than to wait until a hose bursts and you destroy your engine or get stranded.
With the water heater, the lifespan depends on the build quality and how dry the lazarette is. However, 8-10 years is the rule of thumb for replacing a water heater. An Isotemp costs at least double what a Seaward costs, but the Isotemp is likely to last longer. I was leaning towards the Isotemp, but when I went to buy one, the guy steered me towards the cheaper model, saying he would sell me an Isotemp, but he thinks the added $$$ is not worth it for what you get. He said the Isotemp will last longer, but it's more about looks than performance of the water heater. You might have to get an Isotemp slim depending on your space requirements, and on a lot of boats space is the driving factor. Mine required a hole cut to fit a new Seaward, but the Isotemp would've slipped right in.
Those two hoses run from the engine to the water heater. Your first step will be to drain the engine coolant through the 2 small hoses on the side of the engine. Next, you disconnect the two hoses from the engine side first. Since the connection is high up, coolant won't spill out once you remove them since you already drained the engine coolant. Then you try to dump as much coolant out of those hoses as you can before disconnecting from the water heater. I use buckets, milk jugs, and those cheap disposable baking tins from the baking aisle at the supermarket.
Once you remove the two hoses from your engine, you'll want to cap the outlets. You have 2 options for capping these. You can buy caps from a Yanmar dealer (refer to a parts list), or you can go to an Ace Hardware (or wherever you go), and buy (2) 3/8" brass caps (see my photo below for the Ace Hardware version). Be sure to put some plumber's tape on the threads.
Finally, you'll want to disconnect the hoses from the water heater. The ends I removed from the engine could be held lower than my water heater, so I was able to drain out all coolant from the engine size. I then went into my lazarette, and remove the coolant hoses that way. My hoses were decades old, so I had to cut them off. Once they're removed from the water heater, you can pull the hoses through and you're done. It depends where your water heater is located, but this process should be similar for you.
One thing, there is wire in these hoses. I have a pair of snips I use to cut brake cable. You'll want some really good snips, standard scissors or box cutters won't do the trick here, you need something strong.
Once you remove the two hoses from your engine, you'll want to cap the outlets. You have 2 options for capping these. You can buy caps from a Yanmar dealer (refer to a parts list), or you can go to an Ace Hardware (or wherever you go), and buy (2) 3/8" brass caps (see my photo below for the Ace Hardware version). Be sure to put some plumber's tape on the threads.
Finally, you'll want to disconnect the hoses from the water heater. The ends I removed from the engine could be held lower than my water heater, so I was able to drain out all coolant from the engine size. I then went into my lazarette, and remove the coolant hoses that way. My hoses were decades old, so I had to cut them off. Once they're removed from the water heater, you can pull the hoses through and you're done. It depends where your water heater is located, but this process should be similar for you.
One thing, there is wire in these hoses. I have a pair of snips I use to cut brake cable. You'll want some really good snips, standard scissors or box cutters won't do the trick here, you need something strong.
Seattle-Hunter-31: This is off topic but you should replace the white corrugated hose that is connecting your sink drain to the seacock. It's not an appropriate hose for that application. There was another discussion that mentioned that many Hunters used that type of hose incorrectly. That's a flood waiting to happen. Sorry to wander.
I'm way ahead of you.
The previous owner took horrendous care of this boat, and I've had to do a ton of work on plumbing, electrical, the engine, and rigging to get it up to par. I believe most of the plumbing and engine parts to be either original, or at least 20 years old. It's still an ongoing project just to catch up on decades of deferred maintenance.
The previous owner took horrendous care of this boat, and I've had to do a ton of work on plumbing, electrical, the engine, and rigging to get it up to par. I believe most of the plumbing and engine parts to be either original, or at least 20 years old. It's still an ongoing project just to catch up on decades of deferred maintenance.
Unfortunately incorrect on his part. It's insulated MUCH better and has a thermostatic mixing valve that comes with it. The thing that avoids your 6 year old granddaughter from scalding herself when she turns the hot water on after you've been motoring for 3 hours.
That said, I replaced my own Seaward with another one. My boat, my choice.
I agree, we've seen 10-12 years on ours and other C34s.
Hope you guys are still around....looking at changing the coolant on our Hunter 386, Yanmar 3jh3e. So far everything looks pretty straight forward. I did change the antifreeze last year, but just on the engine. Couldn't figure out the water heater hose lines...didn't want to get an air lock. Having said that...it looks like we have a hose spigot installed on one of our water heater lines. Do you think they did this and ran water through the system while dumping the coolant out through the engine ports to clear the system? I do like the air mattress pump idea to clear the water heat lines. Thoughts?
