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Old 20-05-2020, 18:10   #16
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Re: Coolant disappearing

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Originally Posted by a64pilot View Post
You can buy an inexpensive kit that will test for combustion gasses in the coolant.
$30 or $40 bucks. If present itís a head gasket.
If I had a blown head gasket, would I see degraded performance? My engine starts immediately and will turn 3400 rpm at WOT.
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Old 20-05-2020, 18:18   #17
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Re: Coolant disappearing

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If I had a blown head gasket, would I see degraded performance? My engine starts immediately and will turn 3400 rpm at WOT.
Nope, not necessarily, in fact Iíd say loss of compression is unusual.
I am not saying you have a blown head gasket but just there are test kits to test for it.
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Old 21-05-2020, 21:55   #18
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Re: Coolant disappearing

If you see a Mac Tools or Snap On truck, flag them down....they usually sell a kit with various size test caps for pressure testing cooling systems.
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Old 22-05-2020, 01:23   #19
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Re: Coolant disappearing

That Stant tool is very well made and easy to get on Amazon. I got lucky and it fit my boat. You may need to trace down the adapter based on your rad cap. A worthwhile tool to own in my opinion.
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Old 22-05-2020, 10:44   #20
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Re: Coolant disappearing

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That Stant tool is very well made and easy to get on Amazon. I got lucky and it fit my boat. You may need to trace down the adapter based on your rad cap. A worthwhile tool to own in my opinion.
I finally found one that would fit from Advanced Auto... they loan out tools for free...give them a credit card and they charge you to buy the tool and you get a refund when you return it undamaged.

Anyhow...I pressurized to about 25 psi. I did find one hose with a loose hose clamp but it was the one right by the thermostat that takes water from the circulation pump to the heat exchanger...if coolant was leaking there, Id have seen it.

My heat exchanger "radiator cap" is a 50mm cap...in case you have to borrow a pressure tester. I cant imagine that there would be too many variations on the coolant input cap.
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Old 22-05-2020, 14:18   #21
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Re: Coolant disappearing

I'd be careful about 25psi that's a lot for a cooling system.

So does it hold pressure?
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Old 22-05-2020, 14:36   #22
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Re: Coolant disappearing

Yes the pressure held... But when i went back to the boat this afternoon, the coolant level was down a few ounces!

I pressure tested again and the pressure held!

I ran the engine long enough for the thermostat to open and the engine warm up! I've taken a bunch of paper towels and later them out strategically around the heat exchanger and under the motor to see if its dripping out somewhere...

Failing that, I'll plan on disassembling the heat exchanger next week when I can get some new o rings and gaskets. I'm guessing it's got to be done how crossing over to the exhaust cooling water and going out the exhaust.

Meanwhile I just have to keep a supply of antifreeze on the boat!
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Old 23-05-2020, 14:45   #23
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Re: Coolant disappearing

So I topped off the coolant yesterday and ran the engine till it warmed up!

Went back today, no coolant loss overnight... Pressure tested again.

The first time I read the guage in correctly and had pressurized to 2.5 kg... Today I took it to 15 psi as I believe the normal pressure is around 12.5 psi. Pressure held for 30 minutes. I did notice a very small
drip of coolant running out from under the motor! Now that could be a mixture of spilled coolant and see water that collected around the stuffing box that normally runs into the bilge.

If that is in fact coolant then it must be leaking from a gasket between the engine block and the heat exchanger tank! But what I saw today didn't appear to be a big problem.... Think I'm going back tomorrow and put a puppy training pad under the engine to catch any drips. I'll take it to each stringer so it's not laying in the bilge Uber the engine... But rather suspended just under the pan! Run it at the dock and see if there are any major drips!

If I can get to a point where coolant loss is minimal, I dont mind keeping a gallon or two of coolant in the lazarette for refills!
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Old 23-05-2020, 17:59   #24
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Re: Coolant disappearing

Sometimes the circulating pump will drip when the system is pressurized to filler cap pressure and the pump mechanical seal will act as a relief valve if you go too much higher. It may not automatically reseal after over pressuring.
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Old 23-05-2020, 18:16   #25
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Re: Coolant disappearing

I had a very slow coolant leak that I could not find for quite some time. Passed both hot and cold static pressure tests. Finally turned out to be the coolant pump. Had a very slow leak around the shaft seal that only leaked with the engine running and the shaft turning.
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Old 24-05-2020, 00:49   #26
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Re: Coolant disappearing

You could add a bit of UV dye and a blacklight flashlight to trace down the leak
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Old 24-05-2020, 01:37   #27
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Re: Coolant disappearing

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Originally Posted by dennismenace111 View Post
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?
The freshwater coolant from the engine heat exchanger is leaking into the exhaust system salt water circuit and gets expelled when you start the engine.
You can check it by having a look if there is coolant in the accumulator pot, the antifreeze is usually green so its easy to spot.
Check the gaskets or O rings at the heat exchanger.
Heat exchanger tubes corroded?

I had a similar problem some time ago
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Old 24-05-2020, 05:23   #28
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Re: Coolant disappearing

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You could add a bit of UV dye and a blacklight flashlight to trace down the leak
Yep...I saw a test kit like that at the auto parts store..thats the next test...
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Old 24-05-2020, 05:40   #29
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Re: Coolant disappearing

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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.

Easier said than done! Engine access in a 33 year old Watkins 29 is like crawling into a dark drainage culvert ful of spiders and snakes! It's tight, dark and doesn't smell very nice! I usually have to wait for the engine to cool and crawl in over the top of the engine.

A contortionist would have a difficult time accessing from the starboard lazarette thru an 18" x 18" access panel! With a bright drop light, you can see the back of the engine, but can't really do much more than look at it.

It's not an easy engine to access and work on!
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Old 30-05-2020, 12:57   #30
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Re: Coolant disappearing

Ok today I ran the engine with the coolant fill cap off. Every 10 or 15 seconds a bubble would appear! I'm guessing if got a leaking head gasket! The bubble never stops! Every 10 or 15 seconds.... Plop... Another bubble would appear and pop.
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