Just noticed that when the car is running there is suction under the oil fill cap. I'd rather have negative pressure suction than positive pressure that wants to blow oil out of the seals.

My question is how much suction is too much. I've been running down an intermittent 2187 code and the PCV system is on the list of suspects.

The crankcase ventilation hose looks rather new rubber.

The darn code is very intermittent. I can run several hundred miles and no code. This weekend just traveling a few miles I've thrown three codes.

Remove the filler cap and the engine idle changes.

Guy at the parts store, works as mechanic at VW said that a VW will stall and set a code with the filler cap removed.

So how much suction is too much?

 

Read up on the S40/50 oil trap issues - there was a recall for some models in fact. Google "volvo s40 oil trap recall" and you should find some forum posts that can help you see if your symptoms match up.

As to your question - if you put your hand over the fill cap and you find it hard to remove, that's not a good sign... Some people have noted a problem with the cap whistling or is hard to remove when the engine is running...

 

I've read about the recall and some people have had good response from dealers and some have not. Not sure about my local dealer. From what I've read the problem is not suction, the problem exhibited with the oil trap issue is positive pressure. I'm going to check the difference between my S60 and the V50 oil fill hole.

Here is the recall paperwork

http://www.theeshadow.net/files/ew205.pdf

 

There is no too much.

The negative pressure is created by the engine intake system.

 

That is what I thought. I always thought if there are leaking seals you won't get the vac from the intake system because it is leaking past the seals. Plus if you are getting positive pressure something is clogged.

The above is what I always thought but these days I can find myself incorrectly remembering things.