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While waiting for the yard to replace my cutlass bearings I decided to put new zincs in my heat exchangers. The port side came out easily but the one on the starboard side was so badly corroded that the bolt head broke off. I am probably going to pull the heat exchanger because I don't think that there is enough room to drill out the remnants. As luck would have it, the anode on the starboard motor is on the outboard side, directly above the fuel filter.

What is the best, least messy , way to drain the antifreeze out of my heat exchanger, preferably without draining the entire block?

You shouldn’t have to drain the antifreeze from your exchanger.
The zinc is installed on the saltwater side.
Take off the end cap on the side of the zinc.
You should see the corroded zinc and be able to remove it from the inside of the exchanger.

What Donny said, but buy your gaskets for the end before pulling it apart, just in case they take a while to get.

If you have trouble getting the gaskets (I believe there are 2- one large flat gasket and a small o ring for the retaining bolt) Please let me know, I think I have some extras of the large flat gaskets.
TefGel is your friend on the reinstallation.
Please let me know if I can help.
Stephan

If it is useful - the parts for my heat exchangers are:
Large Gasket - https://www.defender.com/product.jsp?na ... d=16114474
Small Washer - https://www.defender.com/product.jsp?na ... d=16114475
The copper end plates are available also if you need them.
I was surprised to find a small tower of sea life had grown on the zinc pencil in my exchangers.
Best,
Stephan

Stephan wrote: I was surprised to find a small tower of sea life had grown on the zinc pencil in my exchangers.

That's just life in general

Stuff will grow everywhere, except where you want it to grow.

Someday I am going to learn not to use an Easy-out. I looked at the fitting where the anode screws into the heat exchanger tank with an inspection mirror. There was a hole right through the center of the remnant of the old anode, looking like a perfect candidate for an Easy-out. I went back to my garage and searched for the set which I had bought 28 years ago to remove a broken manifold stud on my MG but could not find it so I bought another set. I successfully removed the fragments of the old anode but a chunk of the nut which had been brazed onto the tank came off with it.

After a conversation with the boatyard manager I opted for a new heat exchanger rather than having him send the old one out for repair.

At least this time I didn’t break the extracter off in the hole as I did when I tried to use one on
my MG.

Peter

Sorry to hear that. Removing the end of the heat exchanger is always the way to go.

Tony Meola wrote:Peter

Sorry to hear that. Removing the end of the heat exchanger is always the way to go.

Tony,

I actually did pull the end cover first but had no luck getting the remnants of the anode out that way.

I had to replace the port heat exchanger two years ago so I suspected that the starboard one was near the end of its useful life.

when replacing the zincs
i always put a a dab of anti seize on the threads