Why does my engine (Yanmar 4JH) have two oil filler caps?

[Kelpie]

Out of curiosity, why do you suppose my engine has two oil fillers? One in the rocker cover and the other on the fuel pump. They appear to feed the same oil system. And is there any reason to fill using one rather than the other?

 

[RichardS]

That sounds interesting.

Is it on the lift pump or the injector pump?

Richard

 

[coopec]

Yanmar 4JH-4E Oil Filler????

• Thread starter Nick_Pam
• Start date 30 Jul 2007

Yanmar 4JH-4E Oil Filler????

 

[noelex]

Just use whichever is most convenient. Some installations make the use of one of the fill points difficult so Yanmar have helpfully provided two options on some engines.

 

[michael_w]

My Mitsubishi has two oil fillers. Use whatever is most convenient.

 

[neil_s]

The Lister twin cylinder in my last boat had 3!

 

[Kelpie]

Thanks all! I was hoping it would be that simple!

 

[Resolution]

I also have a filler cap on top of my Yanmar 4Jh. I have been using it to fill up with fresh water. Been doing this for more than ten years. The engine does run a little noisy sometimes.........

 

[jiris]

I also have a filler cap on top of my Yanmar 4Jh. I have been using it to fill up with fresh water. Been doing this for more than ten years. The engine does run a little noisy sometimes.........

A good one . But there is a lesson it. I have a broad experience with diesel engines from diagnosing and testing diesel locomotives. From this experience I learned, a combustion engine can run for a surprisingly long period on a water/oil emulsion containing probably less than 30% oil for a very long time without suffering a catastrophic damage. I used this knowledge once when my car engine run out of oil in Transylvania Alps and I had only water to top it up to get to some civilisation about 100 km away.
Not that I would recommend doing it on regular basis, but it can be a lifesaver on the sea one day...