Excess oil use OR blowing core plug.- ? comes first???

[superquag]

Bit of an unusual one.

Vehicle:- Volvo flat 6 turbodiesel route bus. (ex-South Aust bus).

Symptoms:- Water leaking from one of the heads, traced to core plug.
The heads on these engines are independant and they run a dry sump of around 25 litres. - Sight tube on oil tank plus a dipstick.

Action:- Drove the bus over several days, hour or two each run, radiator cap off, adding lots of water every stop. - Takes 10+ litres when left overnight... Coolant has been Pure Tap Water ...

Anyway, its been fixed, and the Mechanic came back with the comment that the oil level was way too low.

Owner's summary is that the low oil caused the overheating which in turn pushed water temp up in the heads which lead to the weakest core plug expiring.

In short, the oil had been allowed to virtually run out, which caused the overheating, resulting in a leak.... so its clearly the driver's fault.

Comments ? Which comes first? -


Leading up to The Leak, very warm weather, no indication of power-loss or "hot" smells, or unusual water-use, overflowing of header-tank or water in the oil.

[bee utey]

Is the dry sump tank covered in fins and out in the breeze? Unless it's designed as an oil cooler I hardly see how it would cause the coolant system to overheat.

[Blknight.aus]

IT could have gone either way in the same manner of the mechanics version of chicken and the egg went...

Did the Headgasket go because the engine was overheated or did the engine overheat becasue the headgasket let go?

you'd be quite surprised at how much heat gets transfered from the engine via the oil in a dry sump configuration, espsecially if its got a cooler in the return or supply line. That said...

Unless the oil system was set up to close off the oil cooler to preserve lube oil in the event of a low oil level, No, low oil should not have led the engine to heat up to the point that the engine pressurised its cooling system to failure without the cooling system already being compromised. If it did I suspect that you would be looking at the straw that broke the camels back type situation.

The reverse however can be true. IF the cooling system is low or not removing heat adequately oil consumption can increase dramatically over normal usage rates.

[superquag]

I'm not a motor-mechanic, which is why I'm asking. :eek: My own limited experience is that lack of coolant/overheating causes oil -use to excess...

The oil tank is a smooth - surface 25 or so litre tank, mounted under the bus behind the LH front wheels,next to the batteries. Because it sits down on its bags when engine off...and due to "Capital Growth" around the waistline.... crawling underneath is not possible.:o

Head gaskets were ok, AFAIK from the initial diagnosis. {" #2 or #3 head is leaking its core plug"} There were no symptoms of funny noises/smells/performance changes that the other driver noticed, and I only picked up the leak whilst out on a job. - LOW Coolant lamp flashed intermittantly when cornering.