Heat exchanger cap partial failure

Valiente · #1 05-27-2007

I mentioned a coolant leak issue a couple of weeks ago on my Westerbeke W-52. While I haven't ruled out other problems like gasket failure, it is fairly evident that I am losing coolant directly from the heat exchanger pressure cap. These fail in time, and if that's all it is, it's not a big deal to replace. The cap reads "14 lbs. PSI max. pressure" or something along those lines, and it is a silver metal cap that I suspect is the typical 2 1/8" size. It still dogs down, but seeps whether it's running or cold, due to what I am guessing is the "head pressure" of the expansion/fill tank, which is a couple of feet higher than the heat exchanger.

My question: Should I be able to find something cheaper than a "marine part" for $40 shipping and handling, like say at an auto parts store? It looks like a freaking radiator cap to me, and if I found one with "15 psi" on it, would I be "taking a big risk"?

Yes, I am new to diesels and heat exchangers.

hellosailor · #2 05-27-2007

Valiente-
Any cap that is the same size AND the same pressure rating, should work. IIRC there are different pressure ratings.
Caps often fail to seal because people have used anti-leak coolant, which typically has sodium silicate in it, which leaves a glassy mineral coating unevenly in places like the seat under the cap. Which then causes...a leak from the uneven seal.
Yet one more good reason not to use anti-leak unless you need it.

Odds are an old-time NAPA store would have a $10 cap that's perfectly good.

camaraderie · #3 05-27-2007

15 lbs is fine if it fits. Simply raises the boiling point slightly but it is really not that precise.

Valiente · #4 05-28-2007

That's what I figured. As far as I know, no anti-leak was used. This is probably the original cap (19 years old) and the O-ring's probably just worn out. Thanks for the advice.

Before I go long-term cruising, I will remove and pressure-test the heat exchanger and will change all engine hoses, and keep the originals as spares. Right now, I'm just looking to avoid refilling the coolant expansion tank every week.

U.S. and Canadian dollars are near enough par at the moment for it not to be a consideration.

hellosailor · #5 05-28-2007

V-
"and keep the originals as spares." After they have dried out, dust them with plain talc (plain cheap talcum powder) and stow them in ziplock bags or sealed containers. The talc apparently stops surface oxidation and aging as effectively as any modern potion you can buy.

Valiente · #6 05-28-2007

Nice advice! I already used Ziplocks and wee bags of silica dessicant for engine spares, but the talc is a good addition. Nothing seems to be broken, but with what Westerbeke charges, I'm not throwing out anything that's got a bit of life left in it.

hellosailor · #7 05-28-2007

Westerbleak? AFAIK they contract out bids for everything and only assemble it. I've heard time and time again that if you can find out what your engine really is (i.e. who really made the block) that NAPA stores generally can find parts from the real maker, or other sources.

I permanently lost all chance of respect for Westerbleak once I head from a rep that they knew painting the rubber parts was wrong--but they did it anyway, because it was easier [read: cheaper] to assemble the entire engine, then paint it all as a finished product. Accountants!

You know why accountants use those #2 pencils with the rubber eraser on top? Because the actuaries told them that way there's only a 50% chance they can be stabbed to death with their own pencils.

Valiente · #8 05-31-2007

Update: I threw in a Gates 16 PSI rad cap on the Westerbeke heat exchanger and ran the engine for ten minutes at dock. No unusual heating up and no leaking. Cost to me: $9. Thanks, NAFTA!

(I'll still overhaul the heat exchanger before I leave. Being the third owner, I have no confidence the zincs were changed enough to last intact another five years.)

hellosailor · #9 05-31-2007

Darn it, Rick, now you'll sour me to Yanmar. I *was* sure I'd seen Yanmars with their rubber parts still unpainted, maybe this is a new trend? Or some efficiency expert trying to get their profits up, huh?

Anyone else who can comment on the paint on new Yanmars, and whether it has been slopped around too far?

Valiente · #10 06-01-2007

I put in heavy dock lines and chafe gear today (now I have to find some monel wire, dammit), and while aboard, I glanced at the coolant tank. Hasn't budged a millimetre. I declare the problem solved (until the next problem).

Thanks for everyone's suggestions. Now I have to sponge up a gallon of coolant from the keel bilge, but that's fine.