Universal M-18 Heat Exchanger

[engineer_sailor]

In trying to establish a baseline for the maintenance of the Universal M-18 on my Catalina 27, I am planning on removing and working on the heat exchanger. I've already winterized the engine and I am on the blocks. Is there any issues with putting an empty (i.e. not filled with antifreeze) heat exchanger back on?

[Maine Sail]

Originally Posted by engineer_sailor

In trying to establish a baseline for the maintenance of the Universal M-18 on my Catalina 27, I am planning on removing and working on the heat exchanger. I've already winterized the engine and I am on the blocks. Is there any issues with putting an empty (i.e. not filled with antifreeze) heat exchanger back on?

Can't freeze with nothing in it...

[BarryL]

Hey,

Just make sure you remember to check / add / burp the coolant system in spring. Don't be surprised if it's difficult to get the air out. Whenever I mess with the fresh water cooling system it takes me a few cycles of bleeding / adding coolant to get all the air out.

Barry

[Stu Jackson]

Barry's right, here's how to do it:

Engine Overheating 101 - How to Burp Your Engine (Reply #6) Engine overheating problem (with Instructions "How To Burp!")

[engineer_sailor]

Thanks for the burping advice.

So I finally got around to pulling the heat exchanger. Overall, I would say it is pretty good shape. I found a local radiator shop and I am going to have it pressure tested and cleaned. I am also going to replace the gasket and add a lock washer.

Upon inspection, it appeared that the zinc hole was plugged and the rumored brass plug was missing. I assumed that an old zinc was lodged in the hole. I used an awl to scratch the metal and it appears to be copper! The part is a Sen-Dure 2737 (also 298633). The threads where the brass plug portion of the zinc appear to be missing or in rough shape. Could the use of a zinc have been optional where the installer/user would have to drill the hole?

If this is the case I am guessing I can ignore the zinc on this heat exchanger and reinstall assuming a clean bill of health from the pressure testing/cleaning? Thoughts? Photos below:

[CalebD]

No photos.

I'm pretty sure that your HX SHOULD HAVE a zinc bolt.

[MarkSF]

If you look at the pics in this thread, what do you have where it says "zinc" in the pic?

Universal M-18 Heat exchanger

Your description isn't very clear but it sounds like the hole has been plugged with a copper plug. Why can't you remove it and install the proper zinc/brass part?

A picture would say a thousand words in this case.

[BarryL]

Hey,

It's not obvious, but the zinc gets threaded into the plug. The plug is steel, the same material as the heat exchange. The inside of the plug has female threads and the zinc threads into the plug and then the plug gets threaded into the heat exchanger.

Barry

[MarkSF]

The ones I bought from the chandlers recently have a zinc part threaded into a brass plug. Definitely not steel.

[engineer_sailor]

Here is another attempt at photos:

https://picasaweb.google.com/lh/phot...eat=directlink

https://picasaweb.google.com/lh/phot...eat=directlink

https://picasaweb.google.com/lh/phot...eat=directlink