might as well check the flame trap and the related hoses as well as the breather box, just in case.
--
Kenric Tam
1990 Volvo 740 base sedan (B230F)
My Volvo 'Project'

I agree with changing the sealing ring on the cap IF you are absolutely sure the flametrap and ALL associated plumbing is not restricted in any way.

With the mileage on your car you need to remove all the hoses on both sides of the flametrap and make sure they are not clogged or restricted- make sure you check the small hose that leads to the brass nipple on the intake manifold and that the opening in the brass nipple is open to the intake manifold. The plastic oil separator mounted on the drivers side of the manifold needs to be removed and cleaned out (especially at your mileage if it has never been done before). You may find the openings are restricted and a drill bit does a good job of removing the buildup.

Failure to eliminate any restrictions could easily result in the crankcase pressure blowing either the front or rear crankshaft seal and then you will be in a world of hurt compared to the task of the described preventative measures. BTDT.

Randy

If oil is not blowing out anywhere else, especially the rear main seal area, and the crankcase ventilation filter has been serviced properly - the most likely problem is the filler cap seal ring itself. I've had to replace that cap seal on both of my turbo engines.

It's common enough that IPD (www.ipdusa.com) stocks a replacement. I think they are about a dollar.