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Old 24 April 2006, 15:11   #1
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Mercruiser 120hp diesel - coolant issue

Hello Ribnet,

We operate the Mercruiser 120hp diesel outdrive in a small RBB workboat. It is good engine, but I have recently noticed a tendancy for it to weep a certain amount of coolant through the top of the filler cap for the coolant expansion tank. There is a small hole in this cap, so it appears to be designed in.

This only happens when the engine is at normal operating temp and the fluid loss doesn't seem to be in great quantities, but I am now getting twitchy over coolant levels and really we shouldn't be loosing any on a 300 hour engine.

Has anyone come across this before,and if so, what is the fix?

Thanks,

t
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Old 24 April 2006, 15:16   #2
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Quote:
Originally Posted by Tideway
Hello Ribnet,

We operate the Mercruiser 120hp diesel outdrive in a small RBB workboat. It is good engine, but I have recently noticed a tendancy for it to weep a certain amount of coolant through the top of the filler cap for the coolant expansion tank. There is a small hole in this cap, so it appears to be designed in.

This only happens when the engine is at normal operating temp and the fluid loss doesn't seem to be in great quantities, but I am now getting twitchy over coolant levels and really we shouldn't be loosing any on a 300 hour engine.

Has anyone come across this before,and if so, what is the fix?

Thanks,

t
You must not fill the expansion bottle . Keep the level to the minimum well below what is recommended.
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Old 24 April 2006, 15:21   #3
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Thanks Andre,

Any idea why? I spend some time on fluid and engine checks so that it doesn't go bang, but if the minimum line is not a minimum I am buggered!

Have you also seen the weeping of fluid on the expansion bottle cap? Or have we just got a duff cap?

cheers,

t
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Old 24 April 2006, 15:31   #4
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Originally Posted by Tideway
Thanks Andre,

Any idea why? I spend some time on fluid and engine checks so that it doesn't go bang, but if the minimum line is not a minimum I am buggered!

Have you also seen the weeping of fluid on the expansion bottle cap? Or have we just got a duff cap?

cheers,

t
I am now operating my third Parker 630 with the Mercruiser 1.7. I learnt this problem the hard way with my first one cos looked at the min / max level and filled the coolant to the max. Well it over flowed and the white GRP under turned blue. My local Mercruiser serviceman suggested I only filled below the minimum level and now only sometimes I get drops overflowing.

Test it by filling below the minimum then after an hour or so of operation check the level and see by how much it will have increased
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Old 24 April 2006, 16:00   #5
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Cheers Andre, that is exactly what we did today (but I was worrying about it, hence post). Out tomorrow so will see. Many thanks for a quick and helpful reply.

t
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Old 24 April 2006, 16:07   #6
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Cheers Andre, that is exactly what we did today (but I was worrying about it, hence post). Out tomorrow so will see. Many thanks for a quick and helpful reply.

t
you are most welcome. Let me know how you get on tomorrow
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Old 25 April 2006, 13:36   #7
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Andre,

All ok today with coolant and engine, once warmed up the level is about a quarter over the Minimum line. Ran from 0700 to 1430 non-stop with the needle not budging from 90 degrees, so I am happy with it.

Weather was a bit poxy though...

Thanks again,

t
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Old 25 April 2006, 14:11   #8
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I am now operating my third Parker 630
i amm verry sory too heer dat.

Itt mite bee tyme too luk att anuvver maik.

gaRf
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Old 25 April 2006, 14:53   #9
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i amm verry sory too heer dat.

Itt mite bee tyme too luk att anuvver maik.

gaRf

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