Yanmar 4LHA coolant overflowing

[timcub]

Here is a pic of what she's doing:

[Fonseca]

I have a similar problem with a Volvo Penta 2030 B.
Even after testing the heat exchanger for leaks, raw water appeared inside the engine fresh water. Also at some 2500 rpm water started to flow from the overflow tube. The hext exchanger element (a cilynder ) displaced inside the block supports in the direction opposite the raw water flow inside the element.
It happened more than once.
We are now exploiting a new fresh water pump.
We also tested gases inside engine fresh water system (to check a possible head gasket failure) but did not revel anything wrong.

[a64pilot]

Do the test for combustion gasses, eliminate that as a problem.
The black soot looking stuff is pretty common and is often rubber from the hoses, but could be soot.

[timcub]

Head gasket found to be leaking from aft 2 cylinders into coolant chamber. Thanks for all replies.

[a64pilot]

Pull the head and check it for flatness and any erosion where it was leaking.
Do NOT let someone talk you into surfacing it to clean it up unless it’s absolutely necessary, doing so can open a can of worms.
Of course if it’s warped or eroded you have no choice.
If it had to be surfaced, I’d be very tempted to have the valves done, which you May have to anyway, you may have to have the valves seated deeper by the same amount that was removed from the head.

Especially if the head gasket is a thin piece of steel, I’m a fan of copper coat myself. Two coats sprayed and let dry before assembly.
Old school is silver paint as it’s powdered aluminum, but I think copper coat is better.

[Wotname]

Originally Posted by timcub

Head gasket found to be leaking from aft 2 cylinders into coolant chamber. Thanks for all replies.

Thanks for posting the update, it is always good to hear about the outcome of these sort of problems.

[Compass790]

What a64 pilot said re doing head, definitely do a valve grind & use gasket cement on head gasket rather than planing head if possible but Yanmar tech might not want to.
I'm a fan of Loctite 518 as it will bridge up to 0.25mm gap but use cement specifically for head gaskets if you wish. 518 works well on pitting.

[timcub]

Head pulled, both block & head were flat. Head was also magnafluxed for cracks. No indication. Engine reassembled yesterday & not sure what sealant Yanmar tech used. He's the expert, I'm just a customer. Going for sea trial today.

[MrX6M]

Hi, I have twin yanmar 4LHA-Stp engines also. just rebuilt the starboard side and been doing sea trials this week. its one thing after another but today I sprung an odd new coolant leak coming from some kind of vent or bleeder fitting. when the fitting stops leaking and then I open the rad cap it just starts pouring out of the fitting again. it has basically drained all of the coolant out of the heat exchanger. What is going on here?! any ideas please??



https://imgur.com/undefined

[MrX6M]

my Myanmar 4lha-stp is leaking coolant from this fitting. eventually it stops then i take the rad cap off and it just starts pouring out. anyone know what is going on here?

[MrX6M]

my Myanmar 4lha-stp is leaking coolant from this fitting. eventually it stops then i take the rad cap off and it just starts pouring out. anyone know what is going on here?




or can anyone just tell me what this fitting is and its purpose?

[Wotname]

It is a coolant drain point. You can remove it and replace with a bung if it is leaking.

[Cadence]

I there a Schrader valve in there?

[pesarsten]

That appears to be a coolant drain fitting. you should be able to put a wrench on the bottom hex head and tighten. No real force needed its a valve !