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Old 30-09-2024, 15:15   #1
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Yanmar 3JH4E Heat Exchanger

My impeller blade disintegrated and trying to ensure I get all the pieces out. How do I remove the cap at both ends of the heat exchanger? Just to inspect the cap ends, do I have to drain the coolant or can I open the caps after shutting off the raw after intake? Do I have to take any other engine parts off to get to the end caps.

Thanks for any guidance. Tom 202-641-0027
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Old 05-10-2024, 14:08   #2
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Re: Yanmar 3JH4E Heat Exchanger

Since not everybody on the planet has your engine, a picture of your heat exchanger would be helpful.

For my Yanmar, the tube stack in the heat exchanger is accessible by removing the end caps, which are bolted on with two machine screws on each side.

Yes, drain the coolant and sea water from the heat exchanger before removing the end caps. Its drain cocks should be obvious.

Follow the hose and pipe from the water pump">raw water pump to the heat exchanger to find the inlet side and remove that cap first. Any large impeller pieces will be stuck there. If you want to look thru the tube stack pipes then you have to remove the other end cap. If you do that, then remove the tube stack and clean it regardless if there are any impeller pieces stuck in the tubes. The tube stack should be removed and cleaned every several years for no other reason than to keep it from getting stuck in the heat exchanger and then it is a b!tch to remove when you *really* need to remove it.

If you are the proactive sort, then purchase the o-ring/gasket set for the heat exchanger end caps before removing them.
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Old 05-10-2024, 14:15   #3
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Re: Yanmar 3JH4E Heat Exchanger

water pump">
AI inserting this into my post and I am unable to remove it is another reason I don't use electronics.
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Old 05-10-2024, 14:34   #4
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Re: Yanmar 3JH4E Heat Exchanger

It is highly likely that all of the pieces are stuck on the end that has the two hoses attached but small pieces could go through the tubes or get stuck in the tubes. Since it sounds like you've never had it apart before I suggest that you follow Kello's advice and give it a thorough cleaning. It is likely that there are scale deposits that should be cleaned off. This can be done with a mild acid. Vinegar will do it given enough time, but I've had better luck using very diluted hydrochloric acid and a brass brush. A welding rod works well to help bust deposits out of the tubes. By all means buy a new set of seals as the 3jh4e heat exchanger has an interesting ability to take a round 3mm o-ring and turn it into a trapezoid which doesn't like to reseal. This heat exchanger takes two o-rings and an end seal for the inlet end. The o-ring is 74.5x3mm if you can't get a Yanmar part. The end seal is a unique Yanmar part as far as I know.

The Yanmar Part Numbers;
Oring 129670-44150
Inlet seal 120322-33050


Buy two sets and put one in your spares for next time.
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