Coolant temperature at idle rpm on Yanmar 4JH5E

[jjorio]

Hello everyone,

I transfer here my previous thread regarding my false-diagnostic on my Yanmar 4JH5E.

So here are the facts :
- Yanmar 4JH5E installed new in 2011. 1500 hours now
- After 25-30 minutes at idle rpm (around 800 rpm) the temperature alarm fires
- When navigating, there is no problem (Done 6 or 7 hours trip)
- No suspicious smoke
- Checked the impeler (recently changed anyway), OK
- Cleaned the raw water strainer, and the water at exhaust seems in reasonable volume
- The temperature at the top of the engine during those 25-30min clearly rises, and is too hot to touch at the end
- At exhaust, the water spit by the engine is suspectedly cold ... this water is not cooling the engine ...

Any clue where should I start from ?
Why only at idle ?
Thanks everyone
Jaad

[Wotname]

Partial blockage in the Heat Exchanger (either coolant or raw water side) perhaps.

Happens at idle because the water pump (coolant or raw water) is not pushing enough coolant or raw water past the partial blockage when engine is idling ?????

More likely to be the raw water side IMHO although you seem to be getting a reasonable flow.

Until you better advice, try inspecting the heat exchanger...

[jjorio]

Thank you for your suggestion.
But what about the temperature of the discharged water at exhaust ?
It should be at least warm in normal conditions ?

[Wotname]

Originally Posted by jjorio

Thank you for your suggestion.
But what about the temperature of the discharged water at exhaust ?
It should be at least warm in normal conditions ?

Which is why it might be the coolant side of the heat exchanger that is partially blocked although this is less common.

Is the discharged water warm when the engine is running at speed under load?

[Wotname]

Can you see if the coolant is circulating when the cap is removed?

[jjorio]

Originally Posted by Wotname

Is the discharged water warm when the engine is running at speed under load?

I'll test it in the next days. Unfortunately can't do it now ...

[Wotname]

By then you might get smarter and better replies from others

[jjorio]

Originally Posted by Wotname

Can you see if the coolant is circulating when the cap is removed?

The engine is still hot, but acceptable temperature.
I tried to remove the cap, it turns, opens, but I can't remove it !!! seems to be blocked. (I didn't put too much force neither, don't want to break it ...)
I changed this cap (old was rusty) a few months ago ...

Also when I opened the cap, there was air pressure inside (like opening a pressure cooker / I had a protection on my hand of course)

The sub tank is quite full, and when I open the cap, the hose bubbles in the coolant contained in the subtank

[jjorio]

There is also this :
Check the picture of the impeller (as I said earlier it is only a few hours old), you can see that one of the wings (don't know how to say) are bent on the opposite side that the others.
Inlet of raw water is on the right side of the picture.
Outlet on the left

Something looks wrong ?

[jjorio]

The picture

[MBWhite]

No slight intended at all, but what you need to do next is buy an "IR (infrared) Thermometer"



You can get these for less than $10 off ebay, walmart, or amazon. Get one with a laser dot so you can see where it is pointing, and you can map pretty accurately what your engine temps are at and where. It works MUCH better than the old way of seeing how long you can hold your hand on something.

[MBWhite]

Originally Posted by jjorio

The picture

I don't think that is enough to cause an issue, but just rotate the engine by hand until that vane is on top where it has more room and flex it back the other way, either just with your fingers or use a pair of needlenose pliers.

[jjorio]

Originally Posted by MBWhite

No slight intended at all, but what you need to do next is buy an "IR (infrared) Thermometer"



You can get these for less than $10 off ebay, walmart, or amazon. Get one with a laser dot so you can see where it is pointing, and you can map pretty accurately what your engine temps are at and where. It works MUCH better than the old way of seeing how long you can hold your hand on something.

Thanks for that !
The problem is that this is impossible to find here. Need to order it and it takes a long time to ship here ...
Maybe other cruisers might have one. I'll check that in the morning.

[MBWhite]

Out of curiosity, where are you located?

These are also often used in professional kitchens, so if you have a friend who works in a restaurant you may be able to borrow one there (they are used for checking temps of freezers and also ovens).

[jjorio]

Originally Posted by MBWhite

Out of curiosity, where are you located?

These are also often used in professional kitchens, so if you have a friend who works in a restaurant you may be able to borrow one there (they are used for checking temps of freezers and also ovens).

I'm in Hiva Oa, Marquesas Islands 1200 persons living in the island.
Very remote