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Old 20-05-2020, 12:32   #1
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Coolant disappearing

My Yanmar 2GM20F, is losing coolant somewhere. Last Sunday I checked coolant and topped it off in the heat exchanger. I motored about for maybe an hour last weekend. Shut down at the dock, cleaned up and went home! Went back to the boat today to find the heat exchanger empty. Put my finger in and nothing inside.

I originally thought it was the water heater so I disconnected and by passed that and it no longer has coolant running through it! Still losing coolant.

Is it possible that the heat exchanger is leaking into the raw water system and coolant is slowly leaking into the exhaust water?

If so, how one go about identifying and confirming that leak? There doesn't seem to be any coolant leaking out the front or back of the engine! No coolant readily visible in the bilge. I've always got a little water in the bilge that the pump can't remove.

Any suggestions on a next step?
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Old 20-05-2020, 13:40   #2
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Re: Coolant disappearing

Check the areas on the engine where coolant might leak out very carefully for antifreeze stains. (Head gasket, HE end caps, hose clamps, etc.) It could be that coolant is leaking and evaporating so nothing shows up in the bilge. Check the contents of the oil pan. Remove the coolant fill cap and pressurize the freshwater system and see if it holds pressure.

Or it could also be a pin hole in the HE tube bundle and the coolant is going overboard with the sea water. Remove the seawater hoses to the HE, plug the openings into the HE and pressurize the HE. Should not leak air into the antifreeze side.
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Old 20-05-2020, 14:32   #3
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Re: Coolant disappearing

Check your engine oil level and color. It may be going there.
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Old 20-05-2020, 14:45   #4
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Re: Coolant disappearing

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Originally Posted by S/V Illusion View Post
Check your engine oil level and color. It may be going there.
Its not in the oil! The oils is black!
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Old 20-05-2020, 14:49   #5
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Re: Coolant disappearing

You know I tried 3 different auto parts store to borrow a pressure test kit! Not one would fit the filler cap on a Yanmar. Really frustrating!

I'm thinking if getting the engine nice and warmed up at the dock! Then shut down and put paper towels all around the heat exchanger and under the hoses to see if any leaks develope when the engine is hot but not running!

Failing that I was going to pull the core to check for leaks!
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Old 20-05-2020, 14:50   #6
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Re: Coolant disappearing

Interesting thing. Coolant never flows into or out of the expansion bottle. It's always the same level.. it never changes.
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Old 20-05-2020, 15:06   #7
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Re: Coolant disappearing

If the coolant isnít showing up in the engine bilge, it is escaping into the raw water/exhaust circuit. There is nowhere else for it to go. The coolant is at a higher pressure than the raw water so it will flow into the raw water circuit through a leak. Possible paths include a leaking heat exchanger, leaking seals around the heat exchanger and a cracked tank/exhaust manifold. Pressure testing is the best way to find the leak. Fill the coolant tank. Pull the raw water exit hose from the coolant tank and pressurize the tank at the radiator cap. If coolant flows out of the tank the heat exchanger or tank seals are leaking. If not the tank may be cracked at the exhaust manifold.
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Old 20-05-2020, 15:12   #8
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Re: Coolant disappearing

I agree... My problem is that I've been unable to get my hands on a cooling system pressure tester that will connect to the Yanmar HE filler CAP. I'm going back to the boat tomorrow to get the filler cap to take to an auto mechanic I know, that works only on Japanese cars... To see if I can borrow his pressure tester. One would think that something like that would be readily available! I've not been able to find one that fits orvtgat has an adapter that fits!
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Old 20-05-2020, 15:28   #9
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Re: Coolant disappearing

Lacking a pressure tester you could remove the heat exchanger and take it to a radiator repair shop. If it tests OK remove the tank and check for cracks. Also check hoses and o-rings.
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Old 20-05-2020, 15:30   #10
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Re: Coolant disappearing

Good idea!
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Old 20-05-2020, 16:54   #11
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Re: Coolant disappearing

You can buy an inexpensive kit that will test for combustion gasses in the coolant.
$30 or $40 bucks. If present it’s a head gasket.
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Old 20-05-2020, 17:12   #12
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Re: Coolant disappearing

If you can't get a pressure tester cap for your engine, there are other places to pressure test. I had a similar problem. The heat exchanger on my engine has a coolant drain plug. I rigged a simple pressure tester using a nipple on the drain hole, connected to a pressure gauge, a shut off valve, and attached to a compressor. Basically works the same as using the radiator cap method. You have to be fast in connecting this setup or you will have coolant all over the place.
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Old 20-05-2020, 17:24   #13
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Re: Coolant disappearing

I just went through this exact scenario about a week ago. I already had the Stant coolant pressure tester and that's what clued me in. The gauge was dropping from 13 psi to 10 in about 5 min.

I removed both sea water lines on my Westerbeke heat exchanger and capped them using spare hose and some plugs. Then I pressurized the heat exchanger using a fitting I had from work. It's basically a 1/4" NPT with valve and pressure gauge and an air quick connect. Connected to my air compressor and carefully bled in 10 psi. Coolant was overflowing from my cap which was not good news.

Then I pulled the entire heat exchanger and tested in a bucket and sure enough it was leaking. All due to zincs that were snapping off when inserted.

Another clue was when I drained heat exchanger I smelled and tasted it. Since I was running engine on land it should have been fresh water but it tasted like antifreeze.

I made a video about this:



And more info in my thread

https://www.cruisersforum.com/forums...er-234194.html

I ordered a new heat exchanger from Lenco and it seems very well made.
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Old 20-05-2020, 17:27   #14
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Re: Coolant disappearing

A compromised heat exchanger core is unlikely to leak into the exhaust, it will possibly drain the coolant out to sea level via the raw water pump and in some circumstances the coolant tank can refill with raw water, particularly where the engine is below or on the waterline but also from the raw water circuit pressure....... close the seacock to confirm or dismiss this theory.
The GM-F heat exchanger is a bit tricky, itís a triple loop system not a plain ol single pass straight through system and if you get the gasket or the core orientation wrong, itís possible to introduce a slow overheat fault into an otherwise perfectly healthy cooling systemClick image for larger version

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Old 20-05-2020, 18:01   #15
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Re: Coolant disappearing

Quote:
Originally Posted by Pitchondesign View Post
If you can't get a pressure tester cap for your engine, there are other places to pressure test. I had a similar problem. The heat exchanger on my engine has a coolant drain plug. I rigged a simple pressure tester using a nipple on the drain hole, connected to a pressure gauge, a shut off valve, and attached to a compressor. Basically works the same as using the radiator cap method. You have to be fast in connecting this setup or you will have coolant all over the place.
I was considering buying an automotive radiator cap and rigging a Schrader valve and pressure gauge on it. I have one more chain auto parts store to borrow a pressure test kit from! Maybe I'll get lucky yet!
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