I am replacing my hot water heater this weekend and as the system has a heat exchanger built into the engine I want to change the antifreeze and possibly flush the system at the same time. Questions: Should I use anything in the system to flush it or just drain? How do you get all the coolant out - I thought of releasing the compression levers and using the starter motor to pump it out? My 1st time to replace the coolant which I understand must be 50/50 mix water and antifreeze. Any helpful hints greatfully accepted. Regards Don
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I flushed last season
This is how I flushed out the cooling system on my Westerbeke 21 last spring. It worked great! First I removed the thermostat, this is the key! On my heat exchanger there is a drain plug, some also have a petcock. I removed the drain plug on the heat exchanger and was able to slip a piece of hose over it and led the hose into the bulge. Once this is done all you have to do is run a garden hose into the radiator. Adjust the hose pressure so you get a good flow through the system. The motor does not have to be running although you can start it up if you want. If your boat is out of the water be sure that you know how to run the engine on the hard. I flushed my engine for about 5 minutes and then started up the engine and flushed for about 5 more minutes. When you finnished. allow the engine to drain. The beauty of having the thermostat out is that when you fill with antifreeze, you are filling the block up directly. Other wise you have to run the engine, heat up, add, stop, cool, run, heatup, add, and so on. When the block is full, replace the thermostat (make sure to have new gaskets).
This is how I flushed out the cooling system on my Westerbeke 21 last spring. It worked great! First I removed the thermostat, this is the key! On my heat exchanger there is a drain plug, some also have a petcock. I removed the drain plug on the heat exchanger and was able to slip a piece of hose over it and led the hose into the bulge. Once this is done all you have to do is run a garden hose into the radiator. Adjust the hose pressure so you get a good flow through the system. The motor does not have to be running although you can start it up if you want. If your boat is out of the water be sure that you know how to run the engine on the hard. I flushed my engine for about 5 minutes and then started up the engine and flushed for about 5 more minutes. When you finnished. allow the engine to drain. The beauty of having the thermostat out is that when you fill with antifreeze, you are filling the block up directly. Other wise you have to run the engine, heat up, add, stop, cool, run, heatup, add, and so on. When the block is full, replace the thermostat (make sure to have new gaskets).
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I am getting ready to do the same to mine 3HM35F. What Yanmar said to do is 1 - buy a cooling system flush from an auto parts store....make sure it is safe for aluminum and add this to coolant. 2 - run engine for 1/2 hour or so to get it to operating temperature 3 - drain system by opening all fittings....mine has 2 4 - remove thermostat and refill with plain water and run engine for about 5 minutes....do this step 3-4 times until water runs out clear 5 - replace thermostat and gasket and refill with orange anti-freeze mixture I think I will take the thermostat out in step 1 to allow better flow right from the start. I would also avoid putting anti-freeze into the bilge as this will be a finable offense if this is to get into the water from your bilge pump and this will be a pain to clean out once there. Just use a bucket and dispose of properly. Good Luck Greg
I am getting ready to do the same to mine 3HM35F. What Yanmar said to do is 1 - buy a cooling system flush from an auto parts store....make sure it is safe for aluminum and add this to coolant. 2 - run engine for 1/2 hour or so to get it to operating temperature 3 - drain system by opening all fittings....mine has 2 4 - remove thermostat and refill with plain water and run engine for about 5 minutes....do this step 3-4 times until water runs out clear 5 - replace thermostat and gasket and refill with orange anti-freeze mixture I think I will take the thermostat out in step 1 to allow better flow right from the start. I would also avoid putting anti-freeze into the bilge as this will be a finable offense if this is to get into the water from your bilge pump and this will be a pain to clean out once there. Just use a bucket and dispose of properly. Good Luck Greg
Did that job this fall ..
3GM30F: I used an standard flush liquid (I did 2 complete flushes and 2 rinses). There is no way to drain the coolant from the water heater circuit, so to facilitate the job I did the following: - Removed one of the water heater hoses from the engine - Inserted a manual inflator pump (used for air mattress's) into the hose - Placed my thumb over the connector on the engine where the hose came from - Had engine coolant drains open - Started pumping air This process blew out all the coolant in the hoses and the water heater out of the drains very quickly. When refilling, I put a funnel into the smae hose I removed, and was able to fill the heater circuit will coolant/flush/water easily. I still ended up with trapped air that required me to top up system a few time after running the engine. After 2 flushes and many rinses, there was still sludge in the system. I will repeat the process again next year. I speculate that the system hasn't been flushed for years.
3GM30F: I used an standard flush liquid (I did 2 complete flushes and 2 rinses). There is no way to drain the coolant from the water heater circuit, so to facilitate the job I did the following: - Removed one of the water heater hoses from the engine - Inserted a manual inflator pump (used for air mattress's) into the hose - Placed my thumb over the connector on the engine where the hose came from - Had engine coolant drains open - Started pumping air This process blew out all the coolant in the hoses and the water heater out of the drains very quickly. When refilling, I put a funnel into the smae hose I removed, and was able to fill the heater circuit will coolant/flush/water easily. I still ended up with trapped air that required me to top up system a few time after running the engine. After 2 flushes and many rinses, there was still sludge in the system. I will repeat the process again next year. I speculate that the system hasn't been flushed for years.
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