How to change engine coolant water

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AMCarter3
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How to change engine coolant water

Post by AMCarter3 »

Can anyone provide some guidance on changing the anti-freeze engine coolant water? I need to do this and I have not been able yet to determine where the lowest drain outlet is on the engines.
Mac Carter
2006 34' PDQ PowerCat "All Heart"; MV 98; twin 100 HP Yanmars
Home Port: Bellingham WA 98229
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Re: How to change engine coolant water

Post by duetto »

hi mac,

there are multiple drain spigots. i believe there is one behind the oil filter, another under the exhaust elbow, and one on the front next to the water pump. i've used flexible plastic hose to drain coolant into a bucket. if you have the yanmar owner's manual the show them.

i use a heavy duty flush and then flush twice with fresh water.
john & diane cummings
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Re: How to change engine coolant water

Post by thinwater »

I spent decades in the engine coolant formulation industry (chemical engineer), and designed, built, and operated one of the larger facilities.

Unless the system has been neglected, never use flushing chemicals. The people who make them (the tech and testing folks--not the sales department) don't even advise them. They contain corrosive chemicals that remove the passivating film developed by the engine coolant, starting corrosion fresh until the new coolant replenishes the film, which can take several months. They should ONLY be used if you have evidence that the engine is scaled, which should never happen if the coolant is changed on schedule. Flushing chemicals nearly always do more harm than good.

Finally, there are no standards for the safety of flushing chemicals, because the tech folks won't approve them. It's pot luck. That should be a hint. Coolants and stop-leaks have ASTM standards.

Just change the AF. Forget the flush. Forget the freshwater. The only time you flush (water only) is changing formulations, not during maintenance changes, though it does not harm... so long as you flush with distilled water. Flushing with tap water, on the other hand, can introduce contaminants (lime and chloride). So just change it.

BTW, the greatest risk to the marine engnie, by far, is saltwater leaking in through the exchanger. If you actually want to do something good, have the coolant tested for chloride when it is changed. It MUST be less than 150 ppm or you have a real problem.
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Re: How to change engine coolant water

Post by deising »

Drew, that was some interesting info you shared there. Thanks very much.

Where would one go about getting the coolant tested for chloride? Do you know if the pressure in the raw water side is higher or lower than that in the coolant side of the heat exchanger? For salt to migrate in, you would assume the raw waters side is higher.
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Re: How to change engine coolant water

Post by thinwater »

There are mail-in services and there are test kits:

http://www.acustrip.com/res/pss/PSS-3300.pdf

Seawatr it typically about 25,000 ppm chloride, and the condemning limit for used engine coolant is about 150 ppm, so even trace leakage is a problem.

This is why there is no such thing as extended service or 5-10 year life in a boat; the same engine manufacturer will have different maint advice for generators than boats. Boats get contaminated with salt.
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Re: How to change engine coolant water

Post by AMCarter3 »

Very helpful. I found the 4 drain valves by getting a little coaching from our local diesel experts. The Yanmar manual was useless -- the pictures for the valves are so small they are not legible. I drained the Starboard engine first because it has the long hoses that feed hot coolant to the heater under the entry door steps. I did a water flush and then refilled with Cat DEAC coolant - 50/50.

After running the engine for 30 minutes in gear at 1000 rpm, it seemed fine -- temp gauge ran up to about 170 and held there. HOWEVER cold air was still coming out from the heater coil & fan under the entry door steps. So, I'm assuming there is AIR in the 2 long hoses from/to the engine that feeds hot coolant to the heater. The hoses (outflow and return) are about .75” diameter and at least 16’ to the heater. That’s a lot of coolant. And there are no relief valves where the hoses connect to the heater to release air.

My diesel tech said “Either crack open the hose clamps one of the hoses and bleed the air, OR take the boat out and run it for 30 minutes at high RPM’s (2500-3000). He says the latter usually works to force coolant into the heater and slowly purge the air. I’m thinking the best way would be to run the engine up to normal temp (170), shut it down and then purge the air by cracking open the hose clamps on “return” hose at the engine. However, I don’t know which hose is the return. Any suggestion?
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Re: How to change engine coolant water

Post by AMCarter3 »

Also, there are 4 drain valves on the Yanmar 100 HP 4JH3-HTE engines: 1) one behind the oil filter (the primary drain); 2) under the exhaust elbow: 3) under the turbo charger unit; and 4) in front under the water pump.
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Re: How to change engine coolant water

Post by thinwater »

This is why most automotive service stations use a machine that changes the AF by displacement, without draining. Some cars are terribly difficult this way. However, normally the problem slowly clears (air is dispersed in the coolant and comes out the expansion tank). If this were not true, small amounts of air that sneaked in through pump seals would always bind high spots.

If this is a common problem, I would consider installing a high bleed valve. Easier than fighting it.
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Re: How to change engine coolant water

Post by AMCarter3 »

Correction... I discovered that the drain valve associated with the mixing elbow is a SALT WATER drain valve, not a coolant system drain valve. And, I also learned from our local Yanmar experts the flow direction of coolant -- See photo.
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Re: How to change engine coolant water

Post by James Power »

Was the 12 volt circulation pump for the auxiliary heater running?
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Re: How to change engine coolant water

Post by AMCarter3 »

James,

What 12 volt circulation pump for the auxiliary heater? I am very curious about this... I am completely unaware of such a pump on our boat. I know there is a breaker on our DC panel called "Heater". But, as far as I can tell, nothing happens when this breaker is turned ON. We only get heat from the heater (under the entrance door) when the Starboard engine coolant is hot and the "Engine heat Fan" breaker is ON.

If you are referring to another thread on this forum about a "pump for the auxiliary heater installed at the companionway steps" <https://is.gd/NxywqR>, our boat does not have such a pump to my knowledge. There is no pump behind the steps on our boat. Please tell me where to find this circulation pump for the auxiliary heater. I've visually traced every inch of the hose loop that sends hot engine coolant to/from the heater. I do not see a pump in this loop. Are you referring to the water pump on the front of the engine?

UPDATE on our air lock issue... I was successful in getting hot coolant up to the heater. I learned from our local Yanmar experts that our STBD engine is NOT designed to “lift” or “push” coolant up the hose loop to the heater. He says the water pump actually “PULLS” or “SUCKS” the coolant our the return hose FROM the heater to move the coolant. It took several steps to get the hose loop to fill with coolant...

1) We installed an air relief valve at the high point in the hose loop to/from the heater.
2) We added as much coolant as possible directly into the hose loop at the top and used the air relief valve to remove as much air as possible. (note that not much air came out)
2) We then ran the engine IN GEAR at 1100 rpm to get the engine hot enough to open the thermostat at the water pump;
3) We then ran the engine OUT-OF-GEAR at 2800 RPM to “SUCK” coolant UP the hose loop; that resulted in warm air from the heater fan unit... success!
4) I shut the engine OFF and to cool down; and then added about 1/2 qt of coolant to replace fluid sucked into the hose loop.
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Re: How to change engine coolant water

Post by James Power »

Mac,

For the boats that had the auxiliary heater install at the factory the usual arrangement was a heater core and fan under the entrance way steps, and a 12 volt pressure pump to aid with flow mounted up high on the starboard outboard hull in the engine room. Not sure why your system is missing the pump. If it was installed there would be screw holes for the pump base mounting in the glass and signs of a coiled up wiring harness.
On a side note, have a look at the heater hose connections to the brass nipples on the engine. Typically these are double hose clamped with the second clamp not seated on the short nipple, just crushing and damaging the hose.

Hope this helps
James
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Re: How to change engine coolant water

Post by AMCarter3 »

James, thanks for clarifying it. I've been spent a lot of hours in that area lately replacing the original loud, ineffective squirrel cage exhaust fan with a higher quality, quieter Jabsco exhaust fan (along with a 12v speed controller. We definitely do not have a pump for the heater hoses in the starboard engine compartment or in the space between the two berths where the heater is located.

However, I'm now guessing that the purpose of the "Heater" breaker on our 12v panel is for such a pump if we had one. I can't think of any other reason for this breaker.
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Re: How to change engine coolant water

Post by James Power »

Mac,

If memory serves, the distribution panel "heater breaker" was to power up the system to a remote switch mounted by the lower helm steps, controlling the on and off for pump and heater blower.
Interesting that the heater still puts out, without the inline pump. Perhaps its not needed to operate, or was designed to extract heat from the engine after shut down.

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Re: How to change engine coolant water

Post by AMCarter3 »

Just to clarify (I mentioned this earlier), our DC panel has a separate breaker to activate the heater fan. Using that breaker, we can get warm air from the heater “radiator” box as soon as the starboard engine’s coolant has heated up.
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Home Port: Bellingham WA 98229
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