Hi,on my 1990 740 turbo i noticed oil commng out from the filler cap.I replaced the seal but my old one looked still good.I compared the two and they seemed identical in flexibility and size.I know my old 740 gle 86 had a clogged flame trap wich caused it to do the same thing.All i did was remove the filter and clean it with carb cleaner and that fixed my problem.Thing is theyre is no such thing on my turbo car or if there is then its in a different place cause i dont see it.The only thing i see is that little container over the oil pump.Could that thing be clogged causing this problem?
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Costa,740 tic 90' 420000kms

The breather box and the plumbing above it (plastic Y-fitting, small hose to manifold, nipple on the manifold) can all get mucked up... as mentioned, check the FAQ on these.

First thing to try: clean all the oil off the inside of the oil cap & gasket before you put it back on. I was getting a leak from a 6-month-old cap/gasket just after I serviced the PCV system... no leaks from there once I started cleaning the cap before replacing.

- Brian '93 945T

Someone just in the last week or so, posted a way to see if your oil breather box is clogged. As I happened to have "flame traps" on my weekend to do list, I gave the method a try. Too cool! Just use a couple feet of 5/8" ID hose (i.e. a garden hose) to actually blow into your breather box. With the oil cap removed, you should easily blow into the box. Slide your hand over the oil filler area, and your blowing becomes difficult. Remove your hand and you can blow freely. I actually had to make an adapter for one of my cars to just blow into the top of the hose that the flame trap fits into, but same deal. It is easy to tell if your box is blocked. Don't know who posted the info, but it was good stuff.

There is no flame trap on the turbos. The breather box can get clogged up though. With the engine running, cold, remove the filler cap and place your hand over the opening. You should feel a suction, like a vac cleaner but not as strong. Then wipe the oil off your hands.

Some folks dump a little oil down the hose going into the breather box and watch it run out oil drain to help clean it and to verify that it is not clogged.

If you have the smaller breather box and no EGR blocking it you can remove and replace or clean it. There is a good FAQ info on that if your up to it. I have the giant breather box with an EGR valve in the way. I'd have to remove the intake manifold on my T to get it out.
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Tom F