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Doorman

Mikuni MX40 Diesel Heater

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We have a Mikuni MX40 diesel heater on our narrow boat and the diagnostic light indicates that the combustion fan is faulty. Does anyone know where to source a service manual for this model heater, as I've tried Mikuni's web site with no luck!

 

Mike

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We have a Mikuni MX40 diesel heater on our narrow boat and the diagnostic light indicates that the combustion fan is faulty. Does anyone know where to source a service manual for this model heater, as I've tried Mikuni's web site with no luck!

 

Mike

 

Mike, please be careful to be absolutely sure of your diagnosis of a faulty fan. I was lead up the garden path once, bought a fan and motor at some horrendous cost from Mikuni and then discovered it wasn't the fan after all. I still have the serviceable original fan motor (minus the fan itself which is transferable) down in the garage now. I can't remember exactly what symptoms led me up the garden path as it was quite a few years ago but, despite my reasonable technical ability, it happened. Just a word of caution.

Roger

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Yes I agree with Roger, ours whilst being pretty reliable over the years, do tend to confuse when it does go wrong. Do treat the flash code with caution. On one occasion after a cold period the unit would not fire up and the flash codes said low voltage, turned out the frost had pushed the water pump out of its housing. Recently a temperature fault code ended up being an air lock.

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We have a Mikuni MX40 diesel heater on our narrow boat and the diagnostic light indicates that the combustion fan is faulty. Does anyone know where to source a service manual for this model heater, as I've tried Mikuni's web site with no luck!

 

Mike

 

I've got a paper version of the service manual & I've got a scanned pdf version of the 6 pages covering assembly & reassembly, but I can't get it to upload right tonight on my dropbox public folder, so pm me your email address & I can email what I have - it's around 300MB tho, as it was done rough & ready on my old Canon portable printer / scanner! If you wanted more of the manual I could have a go at feeding more of it to the venerable beast but that's the only scanner I have available atm...

 

I'll have another go at uploading it & getting a download link tomorrow if I can get signal.

 

Eta: try this link: MX 40 assembly pictures For some reason this isn't working on my Firefox but it is in my Opera browser, so give it a go!

 

Richard

 

Richard

Edited by Lampyrichard

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Cheers Tony,

 

I already have those two documents, but I'm quite underwhelmed at the fact that there's no assembly drawings available from the Mikuni web site. When we had an Eberspacher heater on our other boat, there was plenty of technical info available on line (just as well really)!

 

Mike

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Mike, please be careful to be absolutely sure of your diagnosis of a faulty fan. I was lead up the garden path once, bought a fan and motor at some horrendous cost from Mikuni and then discovered it wasn't the fan after all. I still have the serviceable original fan motor (minus the fan itself which is transferable) down in the garage now. I can't remember exactly what symptoms led me up the garden path as it was quite a few years ago but, despite my reasonable technical ability, it happened. Just a word of caution.

Roger

 

Hi Roger,

 

thanks for the heads up on the diagnostic front! I'll bench test the fan motor before splashing out on a replacement unit and you're right, they are horrendously priced.

 

I seem to recall Gibbo complaining about the service life of these motors on a previous thread, perhaps he'll come along and enlighten me further. What's also annoying, is the fact that although our boat is 14 months old, the Mikuni will only have been used intermittently for six of those months!

 

Mike

 

Mine indicated the circulation pump. Duly removed striped, found to work on the bench.....turned out to be a fuse....opps

 

:lol: If I had a fiver for all the times that I've stripped down electrical components only to discover it was the bloody fuse. At my advanced years now though, that's the first port of call! :P

 

Mike

 

Thanks for the tips so far. As usual on here, good advice is very welcome! :cheers:

 

Mike

Edited by Doorman

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:lol: If I had a fiver for all the times that I've stripped down electrical components only to discover it was the bloody fuse. At my advanced years now though, that's the first port of call! :P

Been there, done that, bought a case of bloody t shirts ;)

 

Tony

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Hi Roger,

 

thanks for the heads up on the diagnostic front! I'll bench test the fan motor before splashing out on a replacement unit and you're right, they are horrendously priced.

 

I seem to recall Gibbo complaining about the service life of these motors on a previous thread, perhaps he'll come along and enlighten me further. What's also annoying, is the fact that although our boat is 14 months old, the Mikuni will only have been used intermittently for six of those months!

 

Mike

 

 

 

:lol: If I had a fiver for all the times that I've stripped down electrical components only to discover it was the bloody fuse. At my advanced years now though, that's the first port of call! :P

 

Mike

 

Thanks for the tips so far. As usual on here, good advice is very welcome! :cheers:

 

Mike

 

I had similar symptoms and it was the fuse. Replaced the fuse and no problems for a year.

 

I know I should not have said that.

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Flash code is very basic it only gives a clue to what is wrong i.e. faulty pump code just means there is a fault somewhere in the pump circuit caused by umpteen possible things.

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Flash code is very basic it only gives a clue to what is wrong i.e. faulty pump code just means there is a fault somewhere in the pump circuit caused by umpteen possible things.

 

Maybe it should be renamed the 'Vague Code' from many of the comments so far!

 

Mike

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Mike,

 

do you have the owner's manual for the MX40? If so, then apart from a load of pictures of the spare parts (which are on the Mikuni UK website) the service manual doesn't really add anything more than the ropey photos I've already posted.

 

If you don't have the user manual then I'll have a go at scanning in the circuit diagrams & iso drawings as well.

 

Richard

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Mike,

 

do you have the owner's manual for the MX40? If so, then apart from a load of pictures of the spare parts (which are on the Mikuni UK website) the service manual doesn't really add anything more than the ropey photos I've already posted.

 

If you don't have the user manual then I'll have a go at scanning in the circuit diagrams & iso drawings as well.

 

Richard

 

 

Good man! :cheers:

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Good man! :cheers:

 

Mike,

 

sorry for the delay, been fixing the boat & away working.

 

For the record, & for anyone searching for MX40 info, here are the original jpeg scans I took from the rather dodgy service manual I have.

 

Page 25

Page 26

Page 27

Page 28

Page 29

Page 30

 

Warning to anyone on slow/ restricted connection, they're approx 250kB each.

 

Mike, do you have the user manual, because if you do there's nothing else really useful in the service manual.

 

Richard

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We have a Mikuni MX40 diesel heater on our narrow boat and the diagnostic light indicates that the combustion fan is faulty. Does anyone know where to source a service manual for this model heater, as I've tried Mikuni's web site with no luck!

 

Mike

 

Hi

Ring these guys at Mikuni 02380528777 they are always helpfull to me and they post stuff out same day, they also service etc at reasonable cost. Hope this helps.

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Hi,

 

If I can return some of the help received on here, I now have a pdf of the full service manual and parts list from Mikuni. The people there were very quick to offer assistance.

 

If anyone would be interested in copies of the documents, please email me on the profile link and I'll be happy to send attachments.

 

Mike

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Hi Mike,

 

I'm new to this forum. Be interested to read your comments on the Mikuni MX40. Thinking of having one fitted to 60ft. Had any big issues with yours?

 

Chris

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Hi Mike,

 

I'm new to this forum. Be interested to read your comments on the Mikuni MX40. Thinking of having one fitted to 60ft. Had any big issues with yours?

 

Chris

 

Hi Chris and welcome to the forum!

 

When we bought our boat, the boatbuilder preferred the use of Mikuni Diesel heaters as he claimed to have had problems with the other two main manufacturers, those being Webasto and Eberspacher. Having installed an Eberspacher on our first boat - a 40' cruiser sterned narrow boat - I would tend to agree with his opinion about that perticular brand. Also, we know other boaters who've experienced problems with Webasto heaters too!

 

My thoughts on the Mikuni are that they are probably the best out of a bad bunch of heaters that were primarily designed to run on white diesel and used as engine pre-heaters on trucks etc., Their adaptation as central heating boilers on boats has come with some criticism due to several factors, one being the fact that they don't appear to enjoy being powered by red diesel.

 

Also, in fairness to the units, they do tend to be mis-used and or wrongfully installed in boats that do not require high output heaters. For instance, we had a neighbour who owned a 57' wide beam boat that had a 9kw Webasto supplying four radiators and a calorifier with heat. The Webasto was over specified for such a heating circuit and constantly went into 'idle mode' due to reaching its optimum temperature too early. The end result was that the boiler coked up on regular intervals, requiring short service periods and being less than reliable in the process. Once the 9Kw unit was swapped for a 5Kw Webasto, the problem disappeared.

 

These boilers need to work hard in order to prevent early carbon deposits building up so its far better to have a smaller boiler working at full output, than a larger one ticking over. Also, in order to prevent this problem of carbon deposits in the combustion chamber etc., they need to run for at least one hour to reach normal operating temperatures.

 

Back to Mikuni's. Having experienced both these and Eberspachers, albeit for relatively short periods of time - three years with the Eberspacher and two years with the Mikuni - I would certainly prefer the Mikuni, if only for the fact that I can service the latter whilst leaving the unit in place on the boat and still connected to the coolant pipes.

This advantage might not apply to all installations so its horses for courses in that respect.

 

As with many of these heaters, spares are not cheap and if you're not inclined to service the boiler yourself, labour charges vary throughout the system and can be expensive. We use ours for two reasons. Firstly, to warm the boat on winter mornings before yours truly peeps out from under the covers (whimp) to encourage the solid fuel fire back into action. This is usually just for an hour. And secondly, to pre-heat the engine during the winter prior to its initial start-up. Please see my thread on this subject in the 'Equipment' section of the forum.

 

If you do decide to opt for the Mikuni, please email me as I have obtained a comprehensive service manual from the manufacturers that I can forward on to you. Although not completely up to date, the manual is essential if you are to avoid expensive mistakes in servicing without one!

 

Mike

Edited by Doorman
  • Greenie 1

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A lot of the perceived poor performance of these F'ingspachers, muckunis and Nevastos is pre The change to low sulphur diesel in Jan 2011. The red diesel bought today is much nearer to road white diesel than before. I woukd there expect a reduction in fault levels due to carbon deposits. However, I expect boat builders will still be installing them on the cheap and not precisely following manufacturers reccommendations so we will still get low voltage faults etc.

Since Dec 2009 our eversplogger has had :-

New boiler

New air pump

2 new glow plugs.

Running time was unrecorded but daily for hit water between August 2011 and March 2012 ( exceot when broken down)

Parts cost for the above was £670.

A lot of money but cheaper than a new unit.

Would I have / pay for another one?

On our current boat yes, since there is no real other option. However since I am having to buy and fit a new calorifier whuch comes with a fitted immersion heater, I do not expect to use the spligger mucv when on shore power over winter.

If I won the lottery and had a new boat built, i would not have one near the boat. Perhaps a two burner range cooker, or a hurricane boiler?

 

Just to add and to be fair to Everspewers, our is circa 1992 so about 20 yrs old.

Edited by jelunga

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Since Dec 2009 our eversplogger has had :-

New boiler

New air pump

2 new glow plugs.

Running time was unrecorded but daily for hit water between August 2011 and March 2012 ( exceot when broken down)

Parts cost for the above was £670.

A lot of money but cheaper than a new unit.

Would I have / pay for another one?

On our current boat yes, since there is no real other option. However since I am having to buy and fit a new calorifier whuch comes with a fitted immersion heater, I do not expect to use the spligger mucv when on shore power over winter.

If I won the lottery and had a new boat built, i would not have one near the boat. Perhaps a two burner range cooker, or a hurricane boiler?

 

Just to add and to be fair to Everspewers, our is circa 1992 so about 10 trs old.

 

So my opinion about Everspoilers was justified then? :P

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So my opinion about Everspoilers was justified then? :P

Yes and no. I reckon 20yrs service isnt bad. Trouble is everything on the boat is now turning 20yrs old and giving up the ghost.

First the Batts Marine fridge failed. Great little fridge. Done well for 20 yrs. i would have got it repaired but too much corrosion. So £370 for new fridge.

Then a few days ago calorifier split and leaks. So £430 for a new one of them.

So is the Ebersplogger a bad bit of kit at 20 yrs old? I do know that spares prices are horrendous but normal for a marine / boaty part!

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