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Old 13-02-2012, 20:33   #1
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Old Coolant Cause a Leak ?

One of our engines (yanmar 40) has recently developed an irritating leak, you know, not really bad but just enough to have to be topped up with coolant after several hours motoring. The mechanic has reported that the leak is from the oil cooler assembly and is due to old coolant. How can this be?

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Old 13-02-2012, 20:49   #2
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The antifreeze becomes acidic and starts to eat the metal Which is why it should be replaced every 3 years
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Old 13-02-2012, 20:52   #3
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As well as it loses it cooling and anti freezing ability
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Old 13-02-2012, 20:56   #4
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Re: Old Coolant cause a leak?

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Originally Posted by Kiwikat View Post
One of our engines (yanmar 40) has recently developed an irritating leak, you know, not really bad but just enough to have to be topped up with coolant after several hours motoring. The mechanic has reported that the leak is from the oil cooler assembly and is due to old coolant. How can this be?

Kiwikat
As well as antifreeze, coolant contains corrosion inhibitors, whose job is (obviously) to prevent corrosion of all the engine components which would otherwise happen when they are exposed to hot water.

The problem is that the corrosion inhibitors get used up. An ordinary coolant should be changed every 2 years to renew the additives and OAT / HOAT coolants (Dexcool) every 5.

A common error is to assume that you don't need antifreeze when you never go to a freezing climate. You do, for the corrosion inhibitors.

As your oil cooler is a heat exchanger between coolant and the engine oil, it is possible that old coolant allowed it to corrode internally.

When was your coolant last changed?
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Old 13-02-2012, 21:15   #5
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Re: Old Coolant cause a leak?

Thanks for the replies guys, now it all makes sense. Unfortunately we have owned the boat for less than a year and the previous owner had assured us that that had all been done etc....... actually he told us a lot of things that have proven to be fiction

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Old 13-02-2012, 21:25   #6
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Re: Old Coolant cause a leak?

Actually we did have the engines fully inspected and serviced when we arrived in New Zealand. The coolant was tested and got the thumbs up so it must have been when the boat sat unloved in Tahiti for 4 odd years, regularly maintained of course (yeah right) that the damage was done. Would that make sense?
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Old 13-02-2012, 21:43   #7
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Re: Old Coolant cause a leak?

Is the oil cooler aluminum? If so, you need to make sure you are using the right grade of antifreeze. And what series is a Yanmar 40?

Also if the cooler is like the JH series the tubes could possibly vibrate and crack.


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Old 13-02-2012, 22:12   #8
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Re: Old Coolant cause a leak?

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Is the oil cooler aluminum? If so, you need to make sure you are using the right grade of antifreeze. And what series is a Yanmar 40?

Also if the cooler is like the JH series the tubes could possibly vibrate and crack.


.
Thanks Delmarry. Not sure about the cooler but yes engine is 3JH3e. The mechanic says he will attempt to fix the cooler as a replacement costs mega$$$$. He will also completely change the coolant in both engines. I do still wonder why when the coolant was ok when he tested it in November has it suddenly become Old Coolant upon springing a leak?
Must have been the old, Old stuff that caused it
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Old 13-02-2012, 22:47   #9
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Re: Old Coolant cause a leak?

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Originally Posted by Kiwikat View Post
Thanks Delmarry. Not sure about the cooler but yes engine is 3JH3e. The mechanic says he will attempt to fix the cooler as a replacement costs mega$$$$. He will also completely change the coolant in both engines. I do still wonder why when the coolant was ok when he tested it in November has it suddenly become Old Coolant upon springing a leak?
Must have been the old, Old stuff that caused it
Is he able to test the type/grade of the coolant? Not likely! Even the colors have changed these days.
I was able to find the Texaco 7998 in a NAPA store. BTW Texaco here is also Chevron now, so it came in a Chevron container. Texaco Service Products
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Old 13-02-2012, 23:12   #10
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Re: Old Coolant cause a leak?

I believe he just used the test strips that tell nitrate, ph levels etc and of course unable to tell anything else. I guess we just have to put it down to experience and hope he can repair the current oil cooler. At least with a complete flush out and starting anew we will now be able to moniter it correctly.
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Old 13-02-2012, 23:22   #11
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Re: Old Coolant cause a leak?

Even in engines with the most religious servicing, the oil cooler can fail. Some components just have a limited life.
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Old 13-02-2012, 23:29   #12
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Coolers are the most prone to fail they have a hard life
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