Author Topic: Coolant Change on Yanmar 4jh3-TE  (Read 13 times)

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Coolant Change on Yanmar 4jh3-TE
« Reply #1 on: January 19, 2018, 07:06:06 PM »
Hey Mechanically inclined (me not so much) Hylas owners,

  Just wondering if anyone has changed the coolant on their Yanmar and would be willing to offer some words of wisdom.  The operating and service manuals are a little obtuse for me.  I need to obviously locate the drains (three I believe) to get the old coolant out...but there is the issue of the hot water heater and draining the coolant in there and the hoses that run too the heater and back to the engine  What I do know...

1) last coolant change was 4 years ago and I only have about 160 hours on the engine since then.
2) I watched the Yanmar guy change it last time and remember at least two drain points on engine (been told there are THREE? (aft of heat exchanger, cross over tube in flywheel area, third somewhere near manifold?)).  Can any one verify the locations??
3) water heater supply/return hoses were disconnected (I think at the water heater (which is physically higher in boat than the engine) to facilitate refilling them.  A funnel was used to refill the hoses with new coolant.
4) the small overflow reservoir was removed and emptied and refilled with new fluid.
5) been told that after refilling the engine with new coolant to run engine with coolant fill cap off for a few minutes. to vent trapped air, then top off.
6) using Dexcool(??) to refill, anyway the same stuff the Yanmar guy used last time.
7) been told I need to heat the new coolant (run engine for a couple minutes) to open thermostat and then top off the coolant.

If anyone has any info/experience doing this I could use some help verifying the correct number and location of  the drains, addressing how to correctly drain and refill  the coolant in the water heater loop, and the correct procedure for ensuring I have the topped off the engine (do I need to run the engine with new coolant to open thermostat to ensure tipoff? do I need to leave filler cap off to allow trapped air to vent?).

Thanks for the help



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