Heat Exchanger ?

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Rick
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Heat Exchanger ?

Post by Rick »

I'm struggling a bit with an engine problem that I think is a heat exchanger problem but wonder if you agree. I have Flushpro's in line with my Raw Water intake for the engines, so when I'm done boating, I hook up a garden hose and flush the engines with fresh water. The Flushpro's have a clear bulb so you can see the water going into the engine....I'll get back to this in a minute. So I'm losing coolant, whether I sit the dock or go out for the day. I'm losing about a half gallon of coolant per day. Last week, I filled the heat exchanger with coolant in preparation to go fishing the next day. The next day came and I checked the heat exchanger and that's when I found out it leaks while I'm at the dock too. But then I noticed that the bulb of the flushpro was coolant green. So I re-flushed (bulb now clear) and refilled the heat exchanger again. Sure enough the next day the bulb was green again. I don't know how coolant is backtracking through the oil cooler, then trans cooler, then through raw water pump and into the bulb. The only thing I can think of is that when I remove the hose from the flushpro, it allows the coolant to 'vent' back through because I have a bad heat exchanger that's leaking coolant into the raw water. So I ordered a new Heat Exchanger that should be here tomorrow evening and I guess we'll see. Am I crazy ? No, don't answer that ! But could this possibly be the problem ? We'll know in another couple of days but I'm wondering if I should consider something else ? Captain Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA
Rick
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franklyprice
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Post by franklyprice »

I would think that the only way you can get coolant in the raw water side is from a leaking heat exchanger. The fact that the heat exchanger has a pressure cap will push the coolant to the side without pressure , and even with out pressure I would guess that just gravity would let it flow down hill. I agree with your diagnosis, DR.
Frank Price
1987 SF "Jeanne Claire"
Rowley Ma
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Rick
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Post by Rick »

Thanks Frank ! Makes me a lot more confident that I bought the right part ! Captain Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA
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retman
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Post by retman »

I replaced the port heat exchanger this spring as for the last two years I would have to top up the expansion tank every couple of times I ran the boat. Has been fine since and this engine runs a bit cooler now than the starboard. Am planning on doing the starboard this off season. (which starts this coming Wednesday)BTW I purchased a Lenco. Other project is to replace the fairing block behind the Port trim tab. Already did the starboard. It leaks and the fasteners have dissolved.
Bill Arnold 1988 33 FBC Merc 454 'Retriever' SOLD
37 DUFFY. Extended House 3126 Cat.
Rick
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Post by Rick »

A new Merc Heat Exchanger = $1,750 Lenco = $625 No brainer ! Captain Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA
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h2ojst
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Post by h2ojst »

Rick, I'm sure you knew this, but heat exchangers are usually rebuildable. I know there's a company around Ft. Lauderdale, Sen-Dure (I think)but also many local radiator shops are set up to do this fairly easily. I've had success in the past.
Joe Tomaini
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Post by IRGuy »

Before I bought "Phoenix" I had an engine survey done on both Cummins 6BT engines. Only minor issues were discovered and repaired. Once I started using her after each use the coolant level of the stbd engine would drop somewhat but if I just ran at idle or low speed there was almost no noticeable coolant loss. I first checked the oil for coolant contamination with no signs of oil leaking into it. Then I went all around the engine looking for leaks.. no sign and no oil in the bilge. I called the tech and we did a pressure check of the coolant system (without the engine running) and could not find any signs of a leak. I finally took the boat to the local Cummins shop and had them try to find a leak somewhere. After they did several experiments they found the problem. They found that the exhaust manifold had an almost invisible crack (that was most likely caused during a "minor overheating" episode the previous owner admitted to.. saying that he noticed the coolant temp rise immediately when he lost a coolant pump drive belt.. but "honestly.. I shut her down immediately at the first sign of overheating". He had lied to me about other things and I suspect he was lieing to me once again. The Cummins tech said the crack was very small (we needed a magnifying glass to see it) and tight when the engine was relatively cool there were no signs of leakage, but as the engine got warmer while running the manifold expanded and allowed the crack to open up allowing coolant to leak from the coolant system into the exhaust. About $1,200 and a new manifold later the leak stopped.
Frank B - IRGuy@aol.com "Phoenix" 1983 FBC Cummins 6Bs - 315HP Wilmington, NC
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Post by Rick »

Thanks guys and another interesting "dufus" story about your previous owner Frank. I considered having the Heat Exchanger repaired but my engines are 19 years old and I thought there was a decent chance of developing another breach once repaired. As it turns out, I went to install the new heat exchanger and two of the fittings were too close together to fit the two hoses. So I had to send it back to Lenco. He said he would repair and I'm disappointed that he just didn't send a replacement. He said he didn't have one in stock but that's not what his website says. Anyway, I should have by Wednesday, we'll see what happens. Captain Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA
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greysole
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Post by greysole »

Hey Rick, Been away for a while. Catching up on what i missed. How did this work out?
Gerard FREEDOM 86 SF 454 Merc Green Pond, Falmouth MA
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Post by retman »

FWIW my Lenco was a perfect drop in.
Bill Arnold 1988 33 FBC Merc 454 'Retriever' SOLD
37 DUFFY. Extended House 3126 Cat.
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Post by Rick »

The Lenco worked out fine, engines were finally in tip top shape for the last two weeks of the season!
Rick
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Post by mouldrp »

Rick, Good call on the replacement over repair, as the repair usually involves sealing off the tubes that show leakage when the coolant tank is filled with water and pressurized with the end caps off. Depending on the numbers of tubes plugged you would run a little bit hotter but be constantly worrying when additional leaks would develop in the other tubes. Been there done that!
Richard Mould 1988 FBC - Sheer Folly Greenwich, CT
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Post by retman »

Yes, after 30 years my guess is its used up.
Bill Arnold 1988 33 FBC Merc 454 'Retriever' SOLD
37 DUFFY. Extended House 3126 Cat.
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