Heat exchanger corrosion?

I have a Ford Lehman SP135 engine. Each end of the exchanger has a gasket, a cap and a bolt which holds to cap in place. Recently I have noted an accumulation of crusty blue/greenish material ringing the cap/gasket/exchanger. The zinc which bolts into the exchanger is healthy.
What does it mean and how can I fix it. Wish I could send a pic but the boat is far away.
Thanks in advance.

Remove the bolt, end caps and rubber gaskets. Clean the ends of the heat exchanger and end caps being careful not to scratch either. Reassemble with new gaskets.

It's nothing to worry about. Its salt/moisture wicking around the heat exchanger ends and caps. The gaskets are cheap and you can even buy new end caps.

What Larry said.

Plus don't forget the plastic washers that go on both sides of the bolt that holds the end cap on. And you can add a little Permatex to help seal the end cap.

Actually now that I think about it the washer that goes on the bolt on the inside of the cap between the cap and gasket is softer like rubber at I recall. The outer washer is nylon under a metal washer.

petdoc4u said:

I have a Ford Lehman SP135 engine. Each end of the exchanger has a gasket, a cap and a bolt which holds to cap in place. Recently I have noted an accumulation of crusty blue/greenish material ringing the cap/gasket/exchanger. The zinc which bolts into the exchanger is healthy.
What does it mean and how can I fix it. Wish I could send a pic but the boat is far away.
Thanks in advance.

Click to expand...

Its probably salt wicking thru. However make sure you clean off the white coating on the zinc.

I sealed my Sendure end cap with Permatex Black, and no gasket. No leaks.
When the impellers tear apart, you got to open that up eventually to get out pieces, which a rubber gasket helps get you going quickly. Just Permatex, you have to wait a while.
On my rebuild, I opened up the heat exchanger and saw some impeller bits and pieces had been there about a year, but I never noticed any issues.

sdowney717 said:

When the impellers tear apart, you got to open that up eventually to get out pieces, which a rubber gasket helps get you going quickly. Just Permatex, you have to wait a while.

Click to expand...

Why should the impellers tear apart? I always figured to replace the impellers long before they would start to fall apart. I think I am missing something again...

Here's what the gasket looks like. They're about 3.75" in diameter but they are called 4" when you order them. They're pretty thick at 1/8". You can order from Fisheries Supply for ~$3/each (manufacturerers part #: SK5400). Before we changed to Al anodes, I had a problem with the zincs breaking off in the heat exchanger when checking them. I got in the habit of taking off the end caps every other zinc change to inspect the tubes and clean out the zinc pieces and installing new gaskets without any gasket sealer. Pretty cheap and easy.

Larry M said:

Here's what the gasket looks like. They're about 3.75" in diameter but they are called 4" when you order them. They're pretty thick at 1/8". You can order from Fisheries Supply for ~$3/each (manufacturerers part #: SK5400). Before we changed to Al anodes, I had a problem with the zincs breaking off in the heat exchanger when checking them. I got in the habit of taking off the end caps every other zinc change to inspect the tubes and clean out the zinc pieces and installing new gaskets without any gasket sealer. Pretty cheap and easy.

Click to expand...

Yep. What he said.

dhays said:

Why should the impellers tear apart? I always figured to replace the impellers long before they would start to fall apart. I think I am missing something again...

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Probably cause I let mine go to long.
It was either old age or it was a jelly fish sucked up against the hull.
I have had jelly fish do that and that does cause impellers to fail.

the one time my impeller disintegrated, there were jelly fish all around the boat. I had just started up after anchoring, within minutes engine overheat, no cooling, entire impeller disintegrated to the metal core.

Another time, running gen at the dock, I had jellyfish actually sucked up into my gen raw water thru hull, before the strainer. Undid the hoses and totally blocked, it was impossible to clear until I used the dock water hose to backflush it out.

sdowney717 said:

Probably cause I let mine go to long.
It was either old age or it was a jelly fish sucked up against the hull.
I have had jelly fish do that and that does cause impellers to fail.

the one time my impeller disintegrated, there were jelly fish all around the boat. I had just started up after anchoring, within minutes engine overheat, no cooling, entire impeller disintegrated to the metal core.

Another time, running gen at the dock, I had jellyfish actually sucked up into my gen raw water thru hull, before the strainer. Undid the hoses and totally blocked, it was impossible to clear until I used the dock water hose to backflush it out.

Click to expand...

Never would have thought of that. I suppose another problem could be a floating plastic bag etc...

How often are you changing the zincs on the heat exchanger? New to me Albin 36 with a Lehman 120.

Islanddreamer said:

How often are you changing the zincs on the heat exchanger? New to me Albin 36 with a Lehman 120.

Click to expand...

It's really a good idea to check them every month or so till you get a feel for how fast they're wasting away. In my case I can get about 150 engine hrs on a set, but it does vary.

Ken

Thanks Ken. There are plenty of things I am discovering. Even though it has less than 3100 hours on it, I want to make sure I stay ahead of the ball.

Interesting to read the forum because things are popping up in my own boat as I am seeing them here.

I check mine every 2 weeks when cruising steadily every day (30-50 miles/5-8 hrs a day)...sometimes it needs it in less than a month/100 hours...other times more.

Next question - for the Lehman 120 model 2715E where can I get replacement zinc pencils?

Islanddreamer said:

Next question - for the Lehman 120 model 2715E where can I get replacement zinc pencils?

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You can get them almost anywhere. They're nothing special, just a brass 3/8" NPT fitting with the zinc pencil threaded into it. The only thing you have to make sure is that they aren't too long. If you put one in that is a bit too long, the zinc will hit the internal boss for the bolt that holds the end cap, and as you tighten the zinc it can break off (inside). Ask me how I know this. The correct length for the pencil is 1 1/2" past the brass plug. That length is not nearly as easy to find as the 2" length. I usually just buy the 2" ones and cut a small piece off the end.

Martyr Marine Engine Pencil Sacrificial Anode

Ken

Thank you sir.

sdowney717 said:

I sealed my Sendure end cap with Permatex Black, and no gasket. No leaks.
When the impellers tear apart, you got to open that up eventually to get out pieces, which a rubber gasket helps get you going quickly. Just Permatex, you have to wait a while.
On my rebuild, I opened up the heat exchanger and saw some impeller bits and pieces had been there about a year, but I never noticed any issues.

Click to expand...

If you lightly coat, just a film, the gaskets on both faces with Teflon grease such a Superlube it improves sealing, and you may avoid the crusty verdigris, which is harmless. In a pinch, if you need to remove the end cap and you don't have a replacement gasket, the lube will often prevent the gasket from tearing. You can use this same technique on raw water pump gaskets. You should always replace these gaskets when removing covers, but again, in an emergency this may allow a re-use.

Steve DAntonio said:

If you lightly coat, just a film, the gaskets on both faces with Teflon grease such a Superlube it improves sealing, and you may avoid the crusty verdigris, which is harmless. In a pinch, if you need to remove the end cap and you don't have a replacement gasket, the lube will often prevent the gasket from tearing. You can use this same technique on raw water pump gaskets. You should always replace these gaskets when removing covers, but again, in an emergency this may allow a re-use.

Click to expand...

I've done it that way for years. The only difference is I put Permatex #2 on one side and Super Lube on the other.

That way I've found the gasket stays sealed to the plate side with the Permatex and pulls off clean from the pump or cooler side coated with Super Lube. And is in the vast majority of the cases reuse able.

Capt.Bill11 said:

I've done it that way for years. The only difference is I put Permatex #2 on one side and Super Lube on the other.

That way I've found the gasket stays sealed to the plate side with the Permatex and pulls off clean from the pump or cooler side coated with Super Lube. And is in the vast majority of the cases reuse able.

Click to expand...

I bet Rector Seal T plus 2 white teflon pipe dope would work sealing a gasket face to metal.
I have used it on all my hose ends including the exhaust hose, and so far no leaks and not sticking of rubber to metal. And when clamped with a hose clamp, no way to twist or pull off the hose, I have tried, they seal and stay on. And when clamp is loosened they slip off without sticking. With that Rector Seal, they also slip on easier.

I had some really bad stuck on rubber hoses when pulling down my engine for a rebuild. You can wreck a hose end for no good reason since it gets stuck while your prying on it, and the rest of the hose is in good condition. Large hoses are expensive so why waste money replacing good hoses because just the ends got stuck and removing them tore the ends up..

You guys with the Sen-Dure coolers, which is many of us, Lehman, Cummins, Westerbeke- The gaskets are generic and available in any good marine supply house.

But don't forget the little rubber donut for the central bolt. Most covers are stamped brass and somewhat concave. Don't overtighten as it can crack the cap, fortunately caps available too.

I do as SD and smear a thin coat of Permatex on the OD of the cooler right before installing cap and gaskets. Keeps it from weeping, which is what causes that corrosion product. Really harmless if it does show up.

I recognize this is an old thread, but figure better to continue an old one than start a new one... I have that nagging drip every few seconds from my heat exchanger cover on my Lehman 120 with a new gasket and no obvious defect on the mating surface of the cap or heat exchanger. I have seen the recommendations above for teflon lubricant, Permatex and Rectorseal. I was leaning toward the Rectorseal #2, but on reflection, I am wondering about Permatex #3 and would appreciate any advice as to what the latest thoughts are on the subject of sealants to prevent dripping. There seem to be a host of new gasket maker and sealer options out there. I date back to when there were only 3 types of Permatex (at least that I knew about).

If the gasket is rubber-like, it is designed to be installed without sealant. I'd look very carefully to see if you can determine why it is leaking. Share photos if you can. If it is rubber, Teflon Superlube would be my recommendation but if there is an underlying issue then that may not work. If there is a surface defect you may need to fil it with something more viscous.

Steve DAntonio said:

If the gasket is rubber-like, it is designed to be installed without sealant. I'd look very carefully to see if you can determine why it is leaking. Share photos if you can. If it is rubber, Teflon Superlube would be my recommendation but if there is an underlying issue then that may not work. If there is a surface defect you may need to fil it with something more viscous.

Click to expand...

The gasket is a round rubber disk that is designed to be installed without a sealant. There must an underlying issue, sine I can’t get it to seal, but it is not visible to me. I will take a picture this weekend. I guess my question is, recognizing that I should not need a sealant, but that I do because it drips without one, what sealant is the best option?

Greetings,
Mr. H. As suggested, I've used Superlube with success. Ours dripped a little as well without any visible source. Not worried what-so-ever with a smear of Sl. Gone. There will be larger things to be concerned with.

RT Firefly said:

Greetings,
Mr. H. As suggested, I've used Superlube with success. Ours dripped a little as well without any visible source. Not worried what-so-ever with a smear of Sl. Gone. There will be larger things to be concerned with.

Click to expand...

Thanks. Under the theory of progressive actions, sounds like the next step is SuperLube. If it still drips after that, I will get more aggressive.

If the superlube doesn't do the trick, try coating the gasket with a thin film of black RTV (on both sides). Then assemble and tighten it down lightly so the gasket and RTV are making contact, but don't tighten the end cap fully. Give it a day to set up, then tighten it the rest of the way and test it out.

Greetings,
NOOOOO! Not silicone, please. Permatex gasket sealer would be better (you can at least clean the Permatex off).

RT Firefly said:

Greetings,
NOOOOO! Not silicone, please. Permatex gasket sealer would be better (you can at least clean the Permatex off).

Click to expand...

Ordinarily I'd agree, but I've specifically had good luck in non-marine applications with RTV getting a questionable surface to seal in cooling system applications. The fact that it cures and will basically form a gasket to shape is part of the key, I think. A non-hardening gasket sealer doesn't always do the trick, although it's probably worth a try first.

I got some Superlube and tried a thin coating. I also spent a little more time scrubbing the surfaces just in case I had missed something before. It did the trick. I put the gasket back on, fired up the engine and no drip. Thanks to all for the advice.