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Old 05-17-2012, 05:30 PM   #1
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Crack in Onan Generator Collant Expansion Tank

Hi all. I found antifreeze under my Onan 8HDKAK-1046K generator. Upon investigation I found a crack in the expansion tank (see photo). It is near the top and we only discovered it when we topped off the antifreeze. It is where the oil fill line goes through the expansion tank (as was discussed here Generator leaking antifreeze)

There seems to be more than enough fluid for normal operation.

We're not near any repair facilities and I am wondering if I can just leave it. The only downside I see is more may slosh out when driving and dust may get in. I don't think the expansion tank is pressurized and the crack is flush to the oil fill line so big stuff probably can't get in.

I could Eternabond the inside the tank but am worried about contaminants, and there isn't room outside because of the oil fill tube.

Any thoughts on how important it is to replace it?

Thanks to all.
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Old 05-17-2012, 07:45 PM   #2
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I would cut the appropriate size of Eternabond and place it on a slick piece of plastic so it could be removed. Then put a small bead of a sealant which is impervious to water and anti-freeze (there has to be something) around the edges. After that drys, put it in the tank to seal.

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Old 05-17-2012, 08:52 PM   #3
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Try calling Cummins with the serial number and ask how much the part is. Sometimes you get a pleasant surprise.
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Old 05-17-2012, 09:30 PM   #4
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its a long standing issue with these puppies
mine was replaced already under warranty x2

give cummins a call
and sprinkle lots of sugar to get one
USN Retired, Life time member of the DAV.
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Old 05-18-2012, 07:28 AM   #5
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Powerboater is correct. This is an ongoing problem with Onan. The old ones seem to crack on a regular basis. Have not heard of a replacement one cracking.Just dish on the bucks and replace it rather than jury rig it and maybe cause other damage later on.
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Old 05-18-2012, 11:16 AM   #6
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Had to replace expansion tank on my QD750 last week for the same reason. Part is about $70 but getting at it is the problem. Warranty co paid over $800 for labor, which included removing the generator from the coach. Water pump was also leaking, which also seems way too common. I have 925 hours on mine. 2007 model.
2002 MCI E4500 bus conversion by American Coach
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Old 05-29-2012, 11:20 PM   #7
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Automotive Goop Epoxy - Goop Paste Epoxy

Industrial Automotive sealer

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Old 05-31-2012, 09:36 AM   #8
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Trpwire beat me to it.. Did not know though that GOOP had an Epoxy product. Do know they have an excelent General Purpose product.

Works well, sticks to just about everything... Do not know how it does with heat but 200 degrees should not bother it.

Foxy-Poxy is another good product but I like GOOP better for this kind of thing.

That said, I don't know how Foxy-Poxy (Swimming pool repair epoxy) stands up to heat either.... Likely not all that well,

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generator, onan, tank

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