6BTA heat exchanger SWEATING ?

[John]

6BTA 5.9 270 HP, JWAC in a boat I bought new in 2006. Home port is Rhode Island. Boat hauled and winterized for 5 months, in the water for 7 months. This is my 13th season, and engine has about 2,000 hours on it. My issue is with the heat exchanger. Over the years, I’ve noticed a little trace of water coming down the rear, bottom hose of the HE. Tightened hose clamp over the years, but essentially ignored it. What little water rolled down the hose, eventually evaporated. Couple of weeks ago, I took a closer look and I see the hose clamp is all rusted, and there’s some verdigris flakes at the hose connection and under the engine. Remove hose clamp, clean up bottom and side of HE tube, and put on a new hose clamp. Days later, I notice a few drops of water accumulating, probably more than I’ve seen since I’ve removed the paint. Now I assume the end cap gasket is leaking. Pull cap off, clean up around the HE tube edge and the cap with 280, 400, and 1000 grit wet/dry paper). When I look into the HE tube, everything is clean (see “he_end”). No crap, deposits, or anything, and some green and red oxidation, which I assume in normal.

As an aside, over the years, I’ll winterize with vinegar flushes, and for the last 10 years, I’ll flush with a 10:1 solution of Acid Magic (buffered pool cleaner), followed by a water and baking soda flush, then a fresh water flush before adding RV antifreeze for the Winter lay-up. In 2015, I ran a recirculating flush with Barnacle Buster for about 1 hour 15 minutes before winterizing. I’ll occasionally do a fresh water flush during the season. Last 2 years, I’m up in a fresh water marina.

I put on a new gasket and washer (see “he_ready”). Start up engine and see what I’ll describe as the edge of the tube at the bevel edge “sweating” water. An extremely small drip (see midpoint “he_drip1”), builds into a larger drip. There is one drip at the mid point of the tube, and another series of drips (maybe 3?) about an inch below. See “he_drip2”, “he_drip_bigger”, and “he_bevel_edge”, marked with a Sharpie lines. At some point, the drips grow big enough to start rolling down the top edge of the bevel to the top of the hose. I’m absolutely certain that nothing is leaking from the cap or gasket. The water droplets are oozing at the top edge of the beveled edge.

So my question is this. Is this some kind of bronze metal failure ?

If a new heat exchanger is in the works, I’m try to get through this season, and work on that over the Winter. For now, I’ve applied a layer of 2-part plumber’s epoxy at the edge where I see the drops (won’t test the results for a couple of days), and I may have to wrap that edge with rescue tape. What say you?

Topic

[Bob Neill]

Glad to hear you resolved your issue, even if it is temporary. Keep us posted if anything changes.

[John]

OK. I applied a 2-part plumber’s epoxy to the “sweating” areas on the tube edge above the bevel. Let it set for a couple of days. Ran a test today, and NO LEAKS. I have no idea what’s going on. I still don’t see any drips from the cap or gasket.

Once the thick coat of original paint started to bubble off (the paint covered cap, exposed gasket, beveled area, and tube), and after I removed more paint to see what was going on, that’s when I saw the obvious oozing. The epoxy may just be short-term fix. If I start to see significant leaking, I’ll order a new cap, gasket and washer. I will also apply a very thin coat of Permatex Form-A Gasket 2A (semi-permanent, non-hardening) on the outside edge of the cap and the flat outside edge of the HX tube. Will see what that does. At the point where I need to pull the HX to resolve a more serious leak, I’ll first start with soldering that edge and a pressure test before going with a new HX.

[Tony Athens]

If the CAP is not cupped (concave in the inside) at least 1/8″, it will not seal on the outside edges .. And do not over tighten. It need to have some “spring tension” in it to seal the outside edge/ring .

Tony

[John]

Bob,

I doubt that cap uncupping is the issue. While running and inspection after the gasket change, I had my eyes inches away from the cap and gasket looking for any leakage at the site. Nothing. Edge of gasket and cap remained dry. The water was oozing from the top edge above the bevel. Weird. That cap and bolt hasn’t been touched since the boat left the factory in 2006. The first time a wrench touched that bolt was a couple of days ago when I pulled the cap to change the gasket. If the consensus is the cap, I’ll just order a new cap.

Sorry about the orientation of the photos guys. Just rotate 90 degrees.

[Bob Neill]

John,

This could be your issue, see link below:

Heat Exchanger Flat End Cap Fix

[Author]

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