Yanmar 4BY2 Oil Leak

[Brian B]

2010 25SC 4BY2-150 Yanmar with 500 hours. I discovered an oil leak when we returned to the boat and could smell oil in the cabin after a 4 hour trip in FL. I removed both engine covers and with the engine at idle could see oil seeping out of a threaded hole. I removed one of the bolts from the bracket that holds the oil sensor and was fortunate that it was the same size, I screwed it into the hole and the oil leak stopped. The pictures are looking at the front of the engine block with the engine covers removed. Oil was seeping out of the hole that the red arrow is pointing to. The stud and nut to the left of the arrow holds the starboard engine cover. With the help of Mack Boring and Winter Island Yacht Yard in Salem MA it was determined that the only thing missing was a bolt. Apparently this would be used on a different application for the engine.
M8 1.25 bolt and flat washer along with LocTite was used for the fix. So far I have not found the original missing bolt. Also there was very little oil lost, I caught this in time.

 

[nzfisher]

Wow. That is pretty scary. An ingenius fix. I guess I need to figure out how to get those engine covers off just in case.

 

[Brian B]

Wow. That is pretty scary. An ingenius fix. I guess I need to figure out how to get those engine covers off just in case.

The covers are held on by four nuts on the front of the engine, the covers are slotted so the nuts do not have to be removed completely. I went through the step to gain access to them, you could feel your way around with a wrench without going through the step. On the port cover there is a bolt on top and a bolt by the fuel filter to remove. Slide cover off to port. The bolt on top is longer than the starboard side bolts so don't mix them up.
Starboard cover has bolts on top to remove and there are two bolts off center going into the engine, just loosen these as the cover is slotted, remove oil fill cap, note how the overflow tube passes through engine components and slide cover off to port. Reassemble starboard cover first as the port cover fits into it.
Install oil fill cap while working to keep anything from entering the engine.

 

[nzfisher]

Thanks. I am saving your explanation and putting it in my manual as I have with so many other valuable tips. I think it is really impressive that you were able to think clearly enough to cannibalize a non essential part to keep the boat running.

 

[captstu]

My Ranger 25's 4by2 has a small oil leak into the bilge. The oil level is not dropping (150 hours since oil change), but the loss continues.

Oil is showing up on "diapers" i put in after cleaning the bilge - the oil is just under the engine coolant pump on the starboard/forward side of the engine.

According to the various diagrams in the parts manual, the oil for the pressure sensor and turbo charger comes from a "bango bolt" in this area.

Access is very tight!

Any idea how I inspect/tighten the fitting that feeds oil pressure to the turbo-charger?

The mechanic who serviced the heat exchanger last clearly worked in this area - but as with other mechanics who have worked on this boat, we won't do any further work without removing the engine. (I paid him about $8k, promptly)

 

[Brian B]

The oil sensor is located under the starboard engine cover on the front of the engine. The sensor screws in, no banjo connections going to the sensor. On my 25 SC I can see the oil line and banjo connections you are referring to from the front of the engine, looking through the step with the covers removed. While you are at it make sure it isn't coming from the bolt hole in my original post on this thread.

 

[captstu]

My 4by2 must be so much different than yours? Both on the engine and in the parts diagram there is a line running from the block to the oil sensor. The same line as a T in it and produces oil that is driven to the turbocharger.

I can’t see the T but it is clear in the print. I’m guessing this is where the leak is because it’s a vulnerable part.

I’m not sure how I’m going to see it to fix it?


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[Brian B]

My 4by2 must be so much different than yours? Both on the engine and in the parts diagram there is a line running from the block to the oil sensor. The same line as a T in it and produces oil that is driven to the turbocharger.

I can’t see the T but it is clear in the print. I’m guessing this is where the leak is because it’s a vulnerable part.

I’m not sure how I’m going to see it to fix it?


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

There was a Yanmar service bulletin on that oil line some years ago, some engines required it's replacement under warranty. Mine was one of them, it was a bear of a job for Yanmar technicians. Don't jump the gun on this being the culprit, there are many locations where an oil leak can occur.

 

[captstu]

Brian,

I’m open to suggestions. I believe the bulletin was applied, but am not sure as Yanmar seems not to keep records and the previous owner didn’t know..

Nevertheless, all leaks are hard to fix and this pipe is in the area, was disturbed during the overheat incident and I don’t see how to inspect any of it.

Still hoping to buy a new engine.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[knotflying]

You should be able to reach down to that banjo fitting and feel it with your hand. I assume if it is leaking there will be some residual oil.

 

[captstu]

What do I remove to reach down?

The fitting seems to be below the heat exchanger... Feeling it was knocked when the heat exchanger was removed 3 times and has been leaking faster since. I can’t figure how to get at it without taxing the exchanger off again.

THANKS


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[knotflying]

You need long arms, but you can get to it. A mirror helps. That fitting is the one that the new line had to attach to, so it is possible to get to it.

 

[captstu]

I have short arms! The leak is very small, but messy. With 180 hours on the oil change, dipstick still well above ‘add oil’. Maybe I just spilled some when filling.

Cleaned mess best I could, still a bit in the bilge, but engine compartment wiped clean, Ran for an hour, can’t see the leak.

Coolant is losing about 8 ounces per hour, can’t see that either. Checked domestic hot water, fittings look ok. I suppose it will get worse, thus easier to find.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796

 

[captstu]

Found an oil leak today: when the mechanic removed and replaced the heat exchanger looking for the engine overheat, he tightened the oil sender finger-tight.

There was a slow drip underway. I applied pipe seal and tightened it.

There may be more oil leaks, bit the dipstick only dropped to just above full so I may have found it.

Loosing water at about 1 cup per engine hour. It may be the domestic hot water heater. I’ll cap it off and see.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796