Yanmar heat exchanger leak?? - SailNet Community
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post #1 of 2 Old 07-01-2013 Thread Starter
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Yanmar heat exchanger leak??

I have a 1996 4jh te (serial #12285) and think the heat exchanger may be compromised. Hereīs what happened. Started with a big mistake - we tried to fill the hot water heater heat exchanger lines at the hot water heater using a hose and a T fitting. (hot water heater is above the engine). We heard fresh water running into the exhaust system at the water muffler. As soon as we heard it, we turned off the water and realized there was a serious problem. Ended up pulling the injectors, shutting off the fuel and then slowly turning over the engine. Sure enough - water was forced out of the injector ports. Since it was all the ports, not just one, Iīm assuming the head gasket is OK and the water got to the cylinders via the exhaust valves.

Reinstalled the injectors and then started the engine. Ran fine. Let it run for 1/2 hr, shut it down, then repeated a couple times to make sure all the water was out and everything is running OK.

My guess is the heat exchanger is compromised allowing fresh water to cross over to the raw water side and into the exhaust system. I canīt think of how else water got into the exhaust system. By using a hose (~30psi) I forced fresh water across to the raw water side, into the water muffler and then back up into the engine through the exhaust. Dumb, but inadvertently found a problem I didn't know about.

Other data:
- coolant level in the heat exchanger does not drop
- no visible leaks into the bilge
- no water in oil
- no detectable levels in any of the fluids (water, oil, transmission, etc)
- engine runs fine, does not overheat

- how do I test the heat exchanger?
- what else could allow water into the cylinders
- if itīs the heat exchanger, do I need to replace the core or the whole assembly?
- If just the core, what else should be checked/replaced at the same time?
- what am I not asking that I should be asking?
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post #2 of 2 Old 07-02-2013
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Re: Yanmar heat exchanger leak??

What if you disconnect raw water out at the injection point of the exhaust and try it again. I see two options .. Youv'e misidentified the ins and outs raw and fresh or the core is about to tell you something.Look out for air lock in hoses above the expansion tank and pressure sensitive tank cap .A good run at temp to remove the last of the water in oil.
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