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Heat Exchanger - possibly trace amount of coolant when changing zinc

B

bobct

Advanced Contributor
I think I might have gotten a trace amount of coolant when I just changed my port side zinc. I have a gallon milk container cut in 1/2 and catch most of what drains out so water isn't pouring all over the engine. I threw the water overboard and noticed a little green fluid left in the residue. Sure looks like coolant. Is that a normal early indicator of a leak? I don't see any noticeable drop in the overflow tank this season and I haven't needed to add any. Temps are perfect.

The heat exchangers are one of the few original parts left on my boat (1988 454). Given the cost and my understanding of how these fail, I wasn't concerned about getting stranded or doing any damage. I guess I'll run it again this week and pull the zinc again.

What do you guys think?

Bob
 
So, if I remove the zinc again and pressure test, I should see coolant dripping out? Is that a valid way to test the internals? I don't believe I have any external leaks. I guess I should try it twice, once hot and once cold.

I fresh water flush almost everytime but there's still 20 years of saltwater use before I owned it.

thanks
Bob
 
Dave, what's been your experience with how these leaks progress? Is it normally one of the tubes? I have a 100 mile round trip planned before the season ends in 2-3 weeks. I'll get a chance to pressure test it before then but wondering if I can just keep an eye on it. If I didn't change the zinc, I wouldn't even know about it. The downside of being on top of maintenance ��
 
Yes. One tube leaks first. I was deep in the islands one time and had to use a couple of bullets to make a temp seal.
 
Its almost always one tube that lets loose.....the pressure difference across it isn't huge but the weak spot usually doesn't take much and then the coolant is lost...

If you an isolate the leaking tube, you can just plug it...going off memory, you can plug 3 holes and still maintain adequate cooling (probably 5 or 6 if you keep the RPMs down)....that said, its likely to be a short period of time before another tube fails.....

New ones are pricey...even the aftermarket brands...a good radiator shop may be able to replace the tube bundles but I wouldn't guess at the cost.
 
When my heat exchanger went raw water forced all the coolant out. The first sign was the level rising in the recovery bottle. As it got worse it would overflow. I routed the overflow hose overboard & ran it for 2 seasons until I replaced the engine. Just be aware that your coolent is being diluted & drain the entire system before freezing weather if you don't fix it.
 
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