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Old 13-12-2010, 21:26   #1
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How to Clean or Descale a Perkins 4.236 Heat Exchanger

A service called heatexchanger Descaler would come to my Cal 46 motorsailer and would clean "descale" my heat exchanger for a fee of $400
I looked around on the web and found that I can get a new heat exchanger for about 4 to 6 hundred dollars.

I am a do-it- yourselfer and am very mechanical. Any recommendations on how best to remove my 1968 Perkins heat exchanger?
What parts would I need? O rings? Any special tools or special things to what out for? Any special precautions?

Is it advisable to fill using a Y valve the heat exchanger with fresh water before turning off engine?

Also what solution besides Muriatic acid would be effective
I am afraid it would dissolve the fine tubes in the exchanger?

I would appreciate a candid reply to:
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Old 14-12-2010, 05:12   #2
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My Perkins knowledge is fairly limited... but first look to see if there are "caps" on the ends of the HE which will allow you to pass a rod through. Alternately rig a circulating pump to pass a diluted muriatic/water mixture through the raw water side. The tubes should be cupronickle and the dilute acid will not hurt it.
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Old 14-12-2010, 06:34   #3
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If you still have the original Serck heat exchanger, it could be removed and then the tube stack could be descaled and pressure tested by a radiator shop. Secure your raw water valve, drain the coolant and salt water, loosen hose clamps and it's held on by two brackets. Radiator shop maybe charges $50.

The main h/e has end caps sealed by rings on the raw water side, and paper gaskets for the connections on the coolant side. Parts are available from Trans Atlantic Diesel. The Serck heat exchangers are quite expensive to replace, thousands of dollars plus time and expense to ship from England. Most people replace with a generic cupro-nickel h/e available for the hundereds of dollars you stated in original post if replacement is needed.
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Old 14-12-2010, 06:45   #4
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I chcked my engine manual for the Perkins 4.108 and it is reccommended that if the tube stack is badly choked that it is immersed in a "Boiling" solution of caustic soda. If the tube are not severly choked it is reccommended that a length of steel rod can be pushed through the individual tubes to dislodge any material, makng sure that the rod does not get pushed into the walls of the tube.
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Old 14-12-2010, 10:26   #5
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Thank you

This is very usefull and givese confidence when I tackle the


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Old 22-12-2010, 15:22   #6
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I have a 4.236 lowline. The exchanger is not so difficult to remove and take apart, so long as the studs holding the saltwater connectors are not seized in the body of the exchanger, which can make it a pig due to lack of space.

Some years ago there was a firm in Palma, Mallorca, offering to chemically descale marine engines. I called them out once, they charged €200, and you would not believe the amount of crud that came out of the engine. When I asked what they were using they said it was a mixture of different citric acids. Oranges and lemons!
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