88 740 wagon, non-turbo.

Years ago I think I read about how you could temporarily reduce excessive crank pressure (I have developed filler cap leaks, despite a new cap and gasket) by using cans of motor flush and pouring them in- I think with the motor running. I think the procedure was to pour the stuff into the little plastic thing next to the valve cover toward the back of the engine, so it runs through the flame trap below. Then change the oil.

I need to order a new flame trap box and the o-ring, but I will need to take a week long trip on Monday, before the parts arrive. I want to do something before I go because I'm losing too much oil.

I can't seem to search the FAQ and find the correct procedure for this temporary fix. Any help much appreciated.