Antifreeze

[valdon34]

I own a 1989 Yanmar 3HM35F. Can anyone tell me how they drain the anifreeze, flush the system, and add new. In other words, a detailed how-to. I'm confused because there are two drainage cocks on the heat exchanger/fresh water tank, and I don't know which to use. Can find no information in either the owners manuel or service manuel.
Valdon

[SteveInMD]

Unless they have been removed or fallen off, there should be clear hoses on the drains you need to use to remove the coolant. The other drains are for the seawater.

There should be one on each side. I don't have that motor or I would tell you more specifically. Don't forget there is coolant running to your hot water heater that should be flushed out. It's also a good idea to remove the heat exchanger core and have it cleaned at a radiator shop. You may want to buy a book on servicing marine diesels for this task. The parts and service manuals are very nice to have also.

When you are finished refill it with Dex-cool pre-diluted coolant.

[welshwind]

I think it might be time to get a new service manual. One should be at the low end of the heat exchanger and another towards the aft end of the block. At least, that is how it is on the 3GM30F. The service manual I have does a pretty decent job of telling me where to look.