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Onan MDKD 6.5 overheaded and shut down


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  #1  
Old 04-12-2017, 02:23:16 AM
Yobbo Yobbo is offline
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Default Onan MDKD 6.5 overheaded and shut down

Hello, just wondering if there is anyone who could help with some Onan advise

I have a 6.5 MDKD-P (I'm located in Australia) in my boat, the other night it overheated and shut down, I pulled up the floor to the engine room and could smell a burning rubber smell and a small amount of coolant on the engine room floor. I waited about 1 hour pressed the reset switch and it started up straight away but with a loud squeeling sound like the belt was slipping, I also checked that it was pumping water out of the exhaust which told me the raw water side is fine ( I also checked the raw water impeller just to be sure). The next morning it started up and ran fine but I could hear what sounded like a bearing noise coming from either the cooling pump or the alternator on the actual engine. so here are my questions

Q What engine does my MDKD use?
Is it a Kubota D950?
If it is a Kubota D950 engine does it use any special Onan circulation / water pump and alternator? or just the standard Kubota one?

Thank you very much, cheers Ian
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Old 04-12-2017, 04:06:24 AM
Yobbo Yobbo is offline
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Default Re: Onan MDKD 6.5 overheaded and shut down

The serial number is E890240974 , cheers Ian
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Old 04-12-2017, 06:04:43 AM
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Default Re: Onan MDKD 6.5 overheaded and shut down

Down load your manuals from http://www.twinslan.net/~n0nas/manuals/onan/
981-0502
981-0600
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Old 04-12-2017, 03:44:23 PM
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Default Re: Onan MDKD 6.5 overheaded and shut down

I would pull the belt off and see whether it is the water pump or the alternator. I have seen both screw up. I dont believe it is anything special for either one just regular Kubota parts. Cheers Dan
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Old 04-12-2017, 06:50:59 PM
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Default Re: Onan MDKD 6.5 overheaded and shut down

Probably the water pump. D650-D950 are the same pump. If it was the little dynamo the machine would have overheated only after the belt snapped and you would have smelled that long before then. Might also want to see if anything blocked the circulation water in the heat exchanger. Gunk or whatever. The MDKC I am working on was pretty disgusting in all the coolant system routing. Doubt it even circulated.
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Old 04-12-2017, 09:35:06 PM
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Default Re: Onan MDKD 6.5 overheaded and shut down

Thank you for the tips, it's in a sound shield and under the flooring right in front of the starboard engine, it's a real pain to get to it, especially someone my size , how can I tell what model of engine it is? Cheers Ian
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Old 04-12-2017, 09:56:00 PM
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Default Re: Onan MDKD 6.5 overheaded and shut down

There should be a CC displacement cast onto the block somewhere. In the case of mine it was below the head, back end of the engine behind the raw water pump. That should get you in the ball park. For example mine is a 675cc engine so its a D650. A D950 has a displacement of 927cc. Otherwise, all those engines look the same. Its like looking at a small block chevy engine and having to guess (if you could not see the balancers anyway). All those SETS look the same. There is a parts set near by that is a 8.0 and looks just like my 4.0. Other than finding the model/serial plate, its hard to tell them apart. Good thing the water pump and the dynamo should be universal for all MDKs. On the land based sets, there are totally different set ups, even if using the same engines.

Last edited by TLB01; 04-12-2017 at 10:10:19 PM.
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Old 06-16-2017, 07:37:17 PM
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Default Re: Onan MDKD 6.5 overheaded and shut down

UPDATE: a big thank you to you all.

I was able to find the model number and it is a D950 Kubota engine. It would appear the wrong sized belt had been installed by the PO and it had started to slip, I replaced the belt with a Gates 7355 (10A0900) and the water pump with a Kubota water pump and also replaced the thermostat (and had the raw water pump rebuilt as preventative maintenance, replaced all oils and coolant with a 50/50 glycol mix) I have now used the genset for around 10 hours and all is working well.

Interestingly when I contacted a local Onan service agent, he told me most people just replace the genset with a new one when the get that old

Thanks again everyone
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Old 06-16-2017, 08:59:56 PM
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Default Re: Onan MDKD 6.5 overheaded and shut down

Quote:
Originally Posted by Yobbo View Post
Interestingly when I contacted a local Onan service agent, he told me most people just replace the genset with a new one when the get that old
Something to know that the dealers "Down Under" tell customers the SAME CRAP as they do here! They don't want you to repair them, all they want to do is sell you a new one!
What is worse is that the older models are better built than the newer ones. Too many electronics on the new ones. Good to know you found the problem and that the protection controls on your older set worked well and saved the set from being ruined.
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Old 06-16-2017, 10:16:01 PM
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Default Re: Onan MDKD 6.5 overheaded and shut down

Quote:
Originally Posted by Yobbo View Post
UPDATE: a big thank you to you all.

I was able to find the model number and it is a D950 Kubota engine. It would appear the wrong sized belt had been installed by the PO and it had started to slip, I replaced the belt with a Gates 7355 (10A0900) and the water pump with a Kubota water pump and also replaced the thermostat (and had the raw water pump rebuilt as preventative maintenance, replaced all oils and coolant with a 50/50 glycol mix) I have now used the genset for around 10 hours and all is working well.

Interestingly when I contacted a local Onan service agent, he told me most people just replace the genset with a new one when the get that old

Thanks again everyone
Ask him why Onans made in the thirties are still working. That was one reason I was fired by Cummins/Onan. I would rather fix things than sell new.
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Old 08-09-2017, 06:22:42 PM
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Default Re: Onan MDKD 6.5 overheaded and shut down

Hi Yobo
I have an Onan 6.5 MDKD as well . Mine is my Carbineer 46. Its done 4000 hrs & runs well ,i recently replaced the orberdorfer raw water pump & most the cooling hoses. I got rid of the metal tube in the water hose & ran a heavy hose that would hold the bend without colapsing. I flushed the cooling system with Cat coolant flush. Its was very clogged up in there needed a piece of wire to unclogg the drain. My board failed & i replaced it $600 not cheap for a very simple circuit. I also replaced the rear bearing in the Alternator a rather difficult job.
I have had difficulty finding what type of Kubota engine is fitted. Cant find any numbers on it. Im wanting to adjust the valves & need the correct tollerances.
If you can show me where you found the D950 id I will look on mine.
Im in Cairns at present leaving to sail up up to TI on Friday.
I see your in Brisvegas.
Mike

Thanks I have been searching for these for ages I owe you a beer.
Mike
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Old 08-09-2017, 08:41:28 PM
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Default Re: Onan MDKD 6.5 overheaded and shut down

There is a casting number on the block directly behind the raw water pump it should say 927cc which would make it a D950 motor. Cheers Dan
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