Yanmar 4JH4E RUNNING HOT!

[Ian_Edwards]

The Yanmar 4JH4E, sounded a high temperature alarm today, there's still water coming out of the wet exhaust, but the oil level is very high.
It doesn't look like water in the oil, so I guess it's diesel.
What's the most likely cause?
Fuel pump?

 

[colind3782]

Probably the lift pump diaphragm. Does the oil smell of diesel?

 

[RAI]

If there is water in the oil, it will make the oil look milky. Sounds like the fuel lift pump.

 

[earlybird]

+1 likely the lift pump. Don't run the engine for any length of time with very high oil level.
The overheating is probably a separate issue. Some checks are:- the raw water intake and filter, pump impeller, vee belt tension, HE coolant level and the thermostat

 

[RAI]

+1 Try checking the raw eater inlet filter, it may be sucking in air.

 

[Mistroma]

Probably the lift pump diaphragm. Does the oil smell of diesel?

I didn't think the 4JH4AE had a diaphragm pump. Mine has a small electric lift pump and used to have a small priming pump on the filter (replaced with a self-bleeding system). I thought that the fuel then went to a vane type pump similar to Jabsco water pumps but with solid sliding vanes rather that flexible ones.

Sudden increase in oil level does sound like a punctured pump diaphragm. Water would be really obvious and fuel would fit the bill.

I'll need to dig out the workshop manual.

 

[Ian_Edwards]

Thanks for all the input.
The first thing I checked was the raw water inlet, and that was clear. There is also water coming out of the exhaust, so there is a least some water getting through the raw water side. No steam comming out of the exhaust, so that side is not getting too hot.
Mistroma is right it's a shaft driven gear pump, no diaphragm. Could a leak on the fuel pump shaft seal cause a fuel leak into the engine?
The engine had been running for about 3hrs at 1800rpm before the alarm sounded.
The oil pressure dropped to about 50% of normal.
I'll check the impeller on the raw water pump today, and the serpentine belt.
The oil is clear, no water, I can't smell diesel, but that doesn't say much, in a hot engine compartment.
I'll also change the oil and filter today, to get the oil level back down to normal.

 

[jwfrary]

Rub the oil between your fingers, does it feel thinner than fresh?

A badly failed injector can cause oil contamination. (Had it on an mtu years ago, had us confused for a little while)

Sure it was overheat and not low oil pressure (from the thinning of the oil)

 

[Mistroma]

Thanks for all the input.
The first thing I checked was the raw water inlet, and that was clear. There is also water coming out of the exhaust, so there is a least some water getting through the raw water side. No steam comming out of the exhaust, so that side is not getting too hot.
Mistroma is right it's a shaft driven gear pump, no diaphragm. Could a leak on the fuel pump shaft seal cause a fuel leak into the engine?
The engine had been running for about 3hrs at 1800rpm before the alarm sounded.
The oil pressure dropped to about 50% of normal.
I'll check the impeller on the raw water pump today, and the serpentine belt.
The oil is clear, no water, I can't smell diesel, but that doesn't say much, in a hot engine compartment.
I'll also change the oil and filter today, to get the oil level back down to normal.

I did check but forgot to post. As far as I could see the 3 cyl. models had a diaphragm pump but the 4 cyl. models did not. I think it was referred to as a "Trochoid Fuel Pump" and mounted on the side of the high pressure pump. Unfortunately, I've never dismantled one and don't know what the innards look like. It seems likely that there must be a seal on the drive shaft and it isn't likely to pass through the high pressure pump inlet side. It would have to reach though to some drive with access to the sump and that makes a leak possible. It does look like a horrendously expensive part, given Yanmar's usual pricing.

I hope you manage to resolve the issue and seem to have the correct approach. The injector issue would probably cause damage to one cylinder if a lot of fuel is passing the rings. I guess you have to try changing the oil but wouldn't want to run the engine for long and monitor the level very carefully on a short run. Perhaps a diesel expert will be able to give better advice of the likely dangers.

 

[hpeer]

FWIW I have a 4JH4TE, 2006 European model, or so I am told.

There is no separate lift pump. Just the injection pump. Obviously something lifts the fuel from the tank so that function must be built into the injection pump. Yours may, or may not, be similar.