Hi
I'm ready for MoTing just in time for Le Mans, apart from one thing; at sustained medium - high revs (sustained for about 10 secs plus) the dry
sump tank starts overflowing into the catch tank. This happens fast enough that the catch tank fills in about 25 seconds (and then overflows
everywhere, as I discovered when I arrived at the MoT centre on Saturday 
), and is happening despite the fact that the tank is only 1/3 full
compared to a recommended 2/3 full. Any ideas?
Cheers!
It sounds like a venting problem.
Assuming that you have the correct volume of oil in the system. In otherwords if you have a 10 litre tank then you only pour in 5 litres, not pour in
oil until the tank is 1/2 full.
When the engine is running the scavenge is (or should be) pumping twice the volume to the pressure side. Most of the scavenge output will be air. So
the tank should have a very good method of seperating the oil and air. This is normally by swirling it around from the top of the tank.
What make is your tank?
John
The tank is fairly basic from Burton Power; it does swirl it around (sort of tangential entry point) and have a couple of internal baffles on the way
down.
I need to check the volume of oil; I'll change it tonight and measure what I put in. I thought the tank should actually be 2/3 full when running.
It's a BMW engine, I think the stated oil change volume for wet sump is 6.5ltrs; it's a 2 gallon tank, how much oil do you reckon I should
put in?
Would an oil cooler in the return line help to seperate air / oil on the way in, and stop oil being carried out of the vent to catch tank?
Pressure is c. 30 psi at idle, not showing more than about 60 at the sort of engine speeds this is happening at.
2 x 12mm vent hoses to breather tank, longer length thatn before and breather tank slightly higher seems to have done the trick - tank now half full
with no oil overflowing.
Thanks for the help
ahhh, was the breather tank lower than the oil level in the dry sump tank? might have started to syphon if the breather pipe got splashed??