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Old 11-02-2010, 06:59 PM   #1
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onan coolant reservior

i noticed an antifreeze leak dripping from my onan 7500. in checking it out it appears the reservior had a small crack in it leaking the backflow after turning the unit off. i have an 06 itasca meridian 39k and guess what? the genset doesn't slide out and i've been told the generator will have to be dropped down in order to replace the plastic reservior.

what a bummer! i was quoted 1,500.00 for the replacement. gosh that is terrible for an inexpensive plastic container. sounds like mostly labor and a too high quote to me.

anyone ever had this situation and is there an alternative fix?

boyce and lisa
06 meridian 39K
06 jeep unltd tow
aventa lx
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Old 11-02-2010, 07:15 PM   #2
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My Onan QD7500 coolant recovery tank also leaks. I have run the generator now for right at a thousand hours with the overflow tank normally empty, and the generator itself doesn't ever seem to lose coolant, it only leaks out what ever I put in the tank. I am at the stage where I am going to drop the generator and change all the hoses, belts, etc. shortly. Once I drop the generator, I will check the tank closely to see if it can be repaired, if it can not be repaired, my local Onan dealer has quoted me a replacement cost for the tank alone of $179.00. I spent about $200 so far for all the hoses, belts, new cap and assorted items to redo everything. Since the generator weighs almost 500 pounds, it is a bit of a job to take out, replace everything and then reinstall.

Depending on the hours you have on your unit, you may want to consider what other items get replaced while the unit is out of the motor home. 1,000 hours is a significant point on the Onan maintence charts.
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Old 11-02-2010, 09:44 PM   #3
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is that including dropping the generator? no?
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Old 11-02-2010, 09:48 PM   #4
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thanks clayton, i've had my mh for 3 yrs. and it hs never shut down due to overheating. i've got 750 hours, so guess i should be thinking about the service thing. it may have been leaking for some time. it's just one of those things that can bug ya.

boyce and lisa
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06 jeep unltd
ox aventa lx
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Old 11-03-2010, 06:52 PM   #5
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Mine leaked for 2 years just like others never had a problelm with the Onan 8K Quiet Generator running. June of 2010 trip to Winnebago Factory Service Center and had it repaired do not know cost since extended warranty covered all but $100.00. I would like to hear how you are planning to drop generator and remove it from RV since service centers put RV on hoist and remove generator with Hy-low.
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Old 11-03-2010, 07:17 PM   #6
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Someone posted here some time ago that he and a neighbor did his genset on a Journey. They put blocks under the front jacks to raise the motorhome pretty high, then used a floor jack to lower the genset. I figured a good motorcycle jack could be used.

However, as much as I'd like to do mine myself (mine will be due a belt and hoses soon), its going to the local Cummins/Onan shop. They estimated 5 hours plus parts. I suspect their shop rate is $120 or so.
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Old 11-04-2010, 07:43 AM   #7
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onan reservior

thanks for the replies. i feel better now that i know others have had this problem and continued to operate the onan. i thought it was closed system and after each running it would pressure more coolant out the crack. i have a policy and will have the work done by onan or qualified service center. i change all the fluids and filters except for the allison. that's one project that's too big for me.

boyce and lisa
06 meridian 39k
06 jeep unltd
os aventa lx
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Old 11-04-2010, 07:02 PM   #8
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Is it impossible to remove the surge tank without pulling the gen out? I know I release the surge tank from the frame each time to change or clean the air filter in my 10kw Onan ...
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Old 11-04-2010, 07:35 PM   #9
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Not familiar with your reserve tank. But mine leaked at the threaded connection. The plastic tank threads were stripped. So, I used an automotive gasket adhesive that is not subject to oil, antifreeze, etc. It doesn't get hard either. I forget the brand. Autozone or Advance carries it.

If you can get to the crack you might want to try and stop the leak. The reservoir is a good way to find out that you have a leak somewhere else before you run it low on antifreeze or worse yet, hot.

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Old 11-04-2010, 09:18 PM   #10
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my onan 8500 had the same thing leak
see pic
our genny is not on a slider either
i found it by removing the top panel screws and then removing the side panel ones and sliding it aft to allow for space to pull the coolant tank out
i had about 6 inches of side clearance to the frame
i then put it back in and had it replaced by cummings under warranty
took the tech less than 2 hrs and he only put the rv on a lift so he could stand instead of lay down
the part that leaked was the fitting that screwed into the lower side of the tank its a 3/8 or so rubber line clamped to a barb fitting
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Old 05-15-2013, 03:21 PM   #11
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I just replaced the Coolant Recovery Tank in my Onan 8000 RV Generator. It had a hairline crack which must be a manufacturing flaw. Of course it is on a slide on my 2006 HR Ambassador. I got a new tank from Cummins for $69.99 and put it on in about 30 Minutes. I had to take the top off my generator which was about 14 bolts but it was easy. I may be talking out of school but yesterday I looked at a friends generator without a slide and it looked like he had room to remove his top without dropping the Generator. In any case call your Cummins guy and he will let you know.
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Old 05-15-2013, 09:37 PM   #12
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A friend of mine was able to get the top off. (Just a bunch of bolts all away around the top.) I think he had one or two on the back side he could not "see" or "get to" so he just pulled up the front part of the cover. A new Cummins' $69 "improved" tank and all is well."
I replaced mine but it was on a slide. It really didn't matter because the hose had a 180 degree "kink" in the line so no fluid was going in or out of the radiator. So, I am not sure it was really necessary to replace it.
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Old 05-15-2013, 10:05 PM   #13
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I haven't tested my "patch" on the coolant overflow tank for my ISC Cummins 8.3L drive engine yet; I patched a 5" crack with a hot glue gun. There is a huge difference between my tank and a generator tank though, the generator tank is in an inclosed space that may reach temperatures high enough to re-melt the glue. Anything you can hold your hand on will not be hot enough to melt the glue.
One guy replied to my post by stating he patched his overflow tank with a soldering iron and a strip from a plastic milk jug.
Of course this would only work if your overflow tank is accessible with both hands.
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