Yanmar 4JH3E Heat Exchanger flush

Expanding on earlier posts on the same topic, I am please to share some lessons learned from my recent challenges of increasing engine temperature and the decision to remove the heat exchanger for a flush. The engine manual calls this out as due every 4 years or 1000 hours so definetly a routine mainenance task.

Following is a descriptive explanation of the process to both remove and reinstall the heat exchanger as follows:

  • Drain the coolant using the drain cock located on the aft side of the heat exchanger housing. You will need plenty of dry rags and a container to collect the coolant ahead of disposal.
  • Loosen the alternator adjustment bolts and remove the v belt allowing the alternator to drop away from the front of the heat exchanger.
  • Remove the 2 hex key bolts holding the fwd heat exchanger cap in place.
  • Tap the cap on the side

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