Rb30det Rear Main Leak - Only After Thrashing

[25GTV]

Hi Guys,

I have a bit of a weird one (I think).

My HR31 has a rb30DET. I have top rocker cover breathers going to a catch can that returns to the sump. I also have a rear head drain to the sump. The PCV is blocked off.

Last night I drove a small drift track after and 3x 4 minute sessions I had no dramas.

After the next session I had about 500ml of engine oil dropping from the bellhousing. Everything else above was dry and leak free.

I then let the car idle and drove 1hr home without dropping any oil. (Maybe 1 or 2 drops)

My questions is, do I need a new rear main seal?

Is it just oil seaping past the seal due to a little blow by?

Has anyone had this same issue?

[Ben C34]

Does your catch can vent to atmosphere?

[89CAL]

Does your catch can vent to atmosphere?

My thoughts as well. It needs some sort of vent (usually PCV does this) vent to atmo otherwise

[25GTV]

Yes the catch can has a large filter to atmosphere.

Is there any other venting on the sump from factory?

Note: the dipstick never blew out etc.

[89CAL]

Def rear main seal? Seems odd if it fixed itself on the drive home

[25GTV]

I think it only leaked while it was being thrashed.

Only wet at the bottom of the bellhousing and not coming from above the gearbox.