Oman MDKBL-5791480 Heat Exchanger

[Jeffrey Cohen]

Need a little advice…

I have the Onan MDKBL-5791480 with 920 hrs (in 2008 boat powered by QSBs with 600 hrs) and I removed the heat exchanger to get at bits of impeller that have broken free over the years.

Now that I have it out should I just pressure test it, paint and reinstall if all is ok or should I just replace it with a new one?

What’s the life span of these anyway?

TIA

Jeff

Topic

[Javier]

Mi Onanismo mdkbl

Hola buenas soy nuevo por aquí .Yo también tengo el mismo generador y cambio el zinc cada año y los filtros de gasoil y aceite,cambio de aceite cada 2 años y la correa y el rodee cada 3 años y va todo perfecto,también lodesmonte una vez para quitar restos del rodee roto, se limpió volvió a montarlo y todo perfecto.
Saludos

[David R Flamer]

Jeffrey, I have the same MDKBL

How long are you typically seeing the HX zinc last? They are not super easy to get to. I am in the process of rigging a fresh water flush to the gen to see if we can stretch it out a bit.

[Jeffrey Cohen]

Unfortunately, other than zincs this heat exchanger was not maintained or fresh water flushed. I pulled it because there was evidence that the end cap gaskets were giving way as well as the impeller pieces.

That being said it seems to be in pretty good condition but I won’t know until I pressure test next week.

Either way I might just replace it and not have to worry about it for the next 9 years and if I can figure out a way to flush it each weekend I will.

Thank for the responses

Jeff

[firehoser75]

Depends on Condition and Testing

Jeffery,
I just had my gen set heat exchanger out in the last few weeks. It looked in good shape (as does the entire generator with the exception of the enclosure base which is rusting). I took it in to a local radiator shop and they cleaned it up and pressure tested it. They found a place on the exterior where it was slightly leaking and repaired it. I gave them new end caps, gaskets, and “O” rings so it should last many more years. It is now 15 years old. Previous owners did not use it much (600 hours) and it was and is freshwater flushed regularly.
Change the zinc regularly (depends on your conditions but I do mine approx. every 3-4 months even though there is still lots of zinc left), change the coolant as recommended, and freshwater flush and a heat exchanger can last a long time. However, if it looks anything like the one in William’s photos, I would probably just replace it and start off with a good maintenance program. For my rusting base, while I had the enclosure apart, I cleaned it up with some mild sanding and applied rust paint. For the bottom, which I could not access much, I just cleaned as best I could and applied several coats of spray on rust inhibitor. Here’s hoping that between ensuring no leaks (I found several small raw water leaks) and my base treatment I can improve the future longevity of my enclosure base.
Good luck,
Tom

[William Walter]

Replace or new

Jeffery I think there are many factors in weather you replace or buy new.i bought new last year while I had generator cover off because of several factors.one I knew the exchanger had never been cared for based on enclosed pictures.two the removal of the cover is necessaryin my setup.i think if you’re unit test ok and has been serviced before you should have many years of service left. I was able to get a good price as I was in no rush and it was a winter project.my exchanger was 14 years old and I’m sure with some basic maintenance it would have lasted longer.bill

[Author]

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