Overheating yanmar

[1tviere]

I have two 14 year old Yanmar 4JHTE diesel engines one is fine and the other one is seriously overheating. I was told that I mixed antifreeze types and this caused a reaction making the coolant turn viscous and I saw what looked like sludge in one of the elbows coming of the cooling system.

We have flushed the system, changed the thermostat, and removed the heat exchanger to clean it but he didn't push the heat tube out of their housing as it risks damage. Now he wants to pull the heat exchanger again and see if he can clean that area.

Any ideas for what to do?

[Wotname]

Have you confirmed the temperature sender and gauge are working correctly?
You swap them with the other engine to confirm.

[Snore]

two questions---

1) how old is the mixing elbow?

2) did you check the strainers?

3) at the dock take both engines to 1500RPM, do they both push the same volume of water out of the exhaust and indicator stream? (The indicator stream is the water that comes out the port forward of the exhaust, if so equipped).

If both engines push the same volume of water out, then it has to be on the fresh water side of the cooling system. Likely culprit is the heat exchanger.

[bgallinger]

Originally Posted by Snore

two questions---

1) how old is the mixing elbow?

2) did you check the strainers?

3) at the dock take both engines to 1500RPM, do they both push the same volume of water out of the exhaust and indicator stream? (The indicator stream is the water that comes out the port forward of the exhaust, if so equipped).

If both engines push the same volume of water out, then it has to be on the fresh water side of the cooling system. Likely culprit is the heat exchanger.

In addition to these very good suggestions I would check the raw water pump for damaged blades and the possibility of broken blades from the impellor stuck in the cooling line to the heat exchanger. I would add that the impellor be changed out religiously every year.

[1tviere]

The raw water pump was changed before I launched. The water flow appears to be same as the other side, the engine gets hot that was confirmed, the strainer is clear only difference is that sometimes I can see air bubbles in the affected strainer but nothing on the good side.

[Manateeman]

Great advice in the above posts. Elbow and exchanger our best choice.
We would look at both engines.
Mark

[Snore]

Originally Posted by 1tviere

The raw water pump was changed before I launched. The water flow appears to be same as the other side, the engine gets hot that was confirmed, the strainer is clear only difference is that sometimes I can see air bubbles in the affected strainer but nothing on the good side.

Ok—- if the same volume of raw water is coming out… Gotta be the freshwater side. Suspects, in order of probability

1) heat exchanger
2) thermostat (recheck)
3) engine water pump (long shot)
4) blockage in engine freshwater water system (same odds as lotto)



I wonder if there is a clear plastic tubing that could take the heat, so you could add it to the line going to or from heat exchanger to confirm water flow?