Reverse flush coolant on my Yanmar?

[bigbrownpilot]

I've been reading about how to flush the coolant out of the Yanmar in my H306. I've read all the standard "open the petcocks and drain" technique, but I'm wondering about using a back-flush kit, like Prestone sells. Someone must have already done this, because there is a garden hose nipple in my heater line to the water pump. Here's what I'm thinking:

Remove the thermostat while the engine is cool. Attach a garden hose with water supply to the nipple. Attach another length of hose to the L-shaped outlet that goes onto the coolant fill port. Add a length of tubing to that, and insert the tubing into a 5-gallon plastic container, and flush out at least 3 gallons, or slightly more than the capacity of the system. When finished, I will have a system full of water. Now, when it's time to re-fill coolant, attach the tubing to the nipple with the 5-gallon container to catch water, start adding 100% coolant into the filler neck, and the coolant should displace the water into the container. Once 2 gallons of coolant are added, close off the nipple and replace the thermostat.

Any ideas or thoughts why this won't work?

Dave

 

[navigator97]

This s waht I did this August. See procedure below

Yanmar 2GM20F Diesel Engine
Fresh Water Loop Drain and Re-fill Procedure.
Rev. of: 24-Aug-12
Fresh Water Drains (2) are located:
1. On Starboard Side at Lower Aft End of Heat Exchanger, w/ a Vinyl Tubing hanging down.
2. On Starboard Side at Lower Forward End of Engine Block, just below the HE Drain w/ a Vinyl Tubing hanging down.
(Note that this drain is on Starboard Side and NOT on Port Side as shown in the Service manual)
See Service Manual pages 8-1 and 8-4 for location of drains and Hot Water Heater hose connections

Steps Task
1 Remove Fresh Water Fill cap at Top Forward End of Engine
2 With Vinyl Tubing in a 1/2 Gallon container, open Starboard Side Heat Exchanger Drain Pet Cock. Drain completely then Close Drain Pet Cock.
3 With Vinyl Tubing in a 1/2 Gallon container, open Starboard Side Engine Block Drain Pet Cock. Drain completely then Close Drain Pet Cock.
4 Drain Sub-Tank (to Port Side of Engine on Bulkhead), and set Sub-Tank aside for now.
5 Disconnect Hose FROM Hot Water Heater at Top Forward Port Side of Engine
(Nearest to Stairs). Hold hose upright slightly above connection port with lanyard or a second person.
6 Disconnect Hose TO Hot Water Heater at Top Forward Port Side of Engine
(Away From Stairs). Hold hose upright slightly above connection port with with your hand, until you place a pail on deck and lower hose into it. Drain as much Fresh Water/Coolant as will come out.
7 Take Hose from Dinghy Air Pump, with it connected to OUT port on Air Pump, put end into the Hose FROM the Hot Water Heater. Slowly pump Air Pump to force air into Heater Hose and force Coolant out of other Heater Hose into Pail. All Fresh Water/Coolant should now be drained (about 1 Qrt.).

8 With one hose held upright slightly above its connecting port with a lanyard or a second person, put a funnel onto the other Heater Hose and pour in 50/50 mix of Shell Rotella ELC Coolant and Distilled Water until is appears near the end of the other Heater Hose, also held upright.
9 Re-connect Hose TO the Heater to it's port on the Top Forward Port Side of the engine (Away from the Stairs) with Hose Clamps.
10 Re-connect Hose FROM the Heater to it's port on the Top Forward Port Side of the engine (Nearest to the Stairs) with Hose Clamps.
11 Put Sub-Tank back in place and connect it's hose assembly to it.
12 Add approximately 1 Gallon of 50/50 mix of Shell Rotella ELC and Distilled Water to the Fresh Water Fill neck. When Level looks right, Re-Install Filler Cap securely.
13 Put same collant mix into Sub-Tank to near the Full Mark.
14 Check that all pet Cocks, Hose Clamps, and Filler cap are Secure.

15 Start Engine and run to circulate coolant. After about 5 minutes, stop engine and re-check coolant level at fill cap. Top off as needed.
16 Run until engine comes up to operating temperature and the thermostat opens (about 15 minutes).
17 When Engine cools down and then is shut off, wait about 15 - 20 minutes before opening Filler cap to Check Coolant Level. Also check level in Sub-Tank. Adjust both levels as needed.

Note: Use same procedure for putting in a coolant Flushing Solution after initial drain and before putting in new coolant.

 

[Ralph Johnstone]

The procedure I use is somewhat simpler.

Drain and fill the engine with 50/50 (using distilled water) every two years. End of procedure.

This has been discussed several times before and I could never see the logic of wanting to remove every last drop of coolant from the engine, hot water heater and attached hoses. If you do a quick drain and fill every two years, you ensure the additives are always up to strength even if you're only removing 50% of the coolant each time. The old coolant doesn't become toxic, the additives just become depleted.

When draining the coolant, I always manage to remove about 2.5 liters whereas the manual specs a 2.9 liter capacity. I can't see the hoses and heat exchanger coils having more than that capacity.

What satisfies me about using this simple method is that the drained coolant looks identical to the new coolant in both clarity and colour.

 

[bigbrownpilot]

My coolant looks really nasty-- almost black in the overflow reservoir. The original owner bought it to sail with his wife and she hated sailing, so it sat for years. Then the next owner bought it and his wife hated sailing, so it sat some more. So I'm dealing with years of neglect, yet the boat is almost like new. So the coolant has probably been changed once, but no idea when. My thoughts on reverse flushing are not because i need to get the last drop out, but because I think it's easier and less mess in the bilge than trying to catch the fluid out of the two block drains and heat exchanger.

 

[Ralph Johnstone]

Now that's a whole different matter. You're probably suffering from accumulations of iron oxide (rust) and quite likely hardness scale depending on the water that was added. The injection and circulation of just water is unlikely to remove this mess. Probably will need something which will chemically attack and remove the deposits but not harm the metals and hoses in the system.

Have you tried a radiator cleaner such as this one by Prestone ?

http://www.prestone.com/products/print/379?popup=1

They claim the cleaning is by chelation but it would be wise to see if it's compatible with the aluminum tubing in your hot water tank.

 

[Robert 47]

The advice and procedure Ralph has stated in the above reply is the best advice you will ever get. I don't know how many people in our harbor even know you should change it. The anti-freeze will break down over time. We change ours like Ralph, every two years. I do the same for the family cars.