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Old 06-26-2011, 02:19 PM   #1
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Heat exchanger question

I just replaced raw water impellers, and one of the impellers was badly damaged.* So I pulled the raw water bonnet off the heat exchanger to pick out the parts of the impeller.* I put everything back together and ran the engine (after replacing belts, filters and impeller) to bring it up to temp and an all around check.* I noticed a slight weep at the base of the heat exchanger bonnet, and assumed I needed to replace the gasket, since I had opened it up.* When I took the bonnet off, I had engine coolant coming out into the raw water side.

I pulled the heat exchanger and took it to a condenser shop.* They disassembled the tube bundle from the exchanger and pressure tested the tube bundle, which passed the test.* The technician noted that the O rings for the tube bundles look flat, so the plan now is to reassemble and pressure test the entire unit.

While the heat exchanger is in the shop, I did a "leak down" test on the other engine - filled the expanson tank to brim full, ran the engine up to about 2/3 throttle fro about half an hour to get up to temp, and then shut down.* At the end, lots of pressure in the expansion tank, no loss of fluid.* So, based on this rudimentary test, it looks like the second system is good.

One added note; this has been a fresh water boat for its service life; I purchased it on Lake Michigan, and have been cruising the Columbia River myself.

So the question is what to do.* Am I approaching end of life (its a 1994 boat), or just seeing bad seals, perhaps from the 6 month winter dry layups.

A replacement unit is $2 boat units, and significantly about a week away, which is getting close to my planned departure for the offshore run to Canada.

Any thoughts, advice?


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Old 06-26-2011, 11:04 PM   #2
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RE: Heat exchanger question

Sound like a seal problem. *It doesn't take much wear on an O ring to allow a leak under pressure which will contaminate the coolant side of the system. *But you should also mention your engine make and which cooling system. *Maybe someone who has your setup and has some knowledge of this problem. *

Mine are 6.354 Perkins and the tube bundle is inside of a bronze pipe , they use a large flat rubber washer and a plate with a bolt in the center on both ends of the pipe to seal and keep the two systems seperate and they are prone to leaking over time.*

Also you mention you are going to Canada; I buy all my heat exchangers from The Manifold Wearhouse. *They are a good source, reasonably priced and they are located in Vancouver, BC. They also have a website to order from online for quick service.*

Good luck


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Old 06-26-2011, 11:18 PM   #3
City: Carefree, Arizona
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RE: Heat exchanger question

On many engines, a bad seal on a HX will not leak coolant, only raw water. If you damaged your RW pump impeller, does this mean overheating occurred? Coolant may be coming from elsewhere if so.

For decades, my mantra has been impellers*replaced every 18 months. They look good when they come out, just as they should. Catch them early and you'll never be picking out rubber parts, or worse. After 17 years, a new tube bundle is not out of the question. If the old one tests out good, you have a spare. But first, find the source of the coolant leak.
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Old 06-27-2011, 05:31 AM   #4
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RE: Heat exchanger question

We have the Ford Lehman SP135.* We were told that the heat*exchanger*should be replaced every 15 to 20 years regardless of how it tests.* We installed a SeaKamp*for less than $800.00.***
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