Cracked OE Plastic Oil Filler Cap. Is This Common?

[Tiger_kpt]

As above really. Bought the car. Did an oil top up on it and noticed that the standard plastic oil cap had a 1cm crack in it, but didn\'t LOOK as though it was all the way through it, so put it back on.
 
I noticed that the oil pressure was a bit random through using the car and so decided to use a CNC machined metal cap. Installed it the other day and the oil pressure seems ALOT stronger and consistant.
 
Also... when it came to removing the cracked OE cap to top up the oil every time over the last two months or so... it was an absolute b*tch to get off. Seemed ALOT tighter than the level which I had originally screwed it on at. This puzzled me.
 
Just wondered if this was a common problem? What your thoughts on this are? Whether they crack for a reason and what problems a cracked oil cap could cause on the engine?
 
Thanks guys.
Kyle.

[jonrx7uk]

They always seem a bit tighter when you ccome to take them off again!  Interesting about the oil pressure though....

[Ricco_04]

The standard one on my FD was cracked - replaced it with another OE one and all is fine for the moment at least.

Maybe it\'s just done up too tight so after a few times of using the car its just under too much strain? Just a guess dunno really! :3Confused

[kermit]

Had the same happen on my last FD.  My thought was that heat from the engine bay probably made it brittle over time.  Constant warming up and then cooling down.

[NurburgRob]

Just discovered that mine has now cracked, it wasn\'t like that less than a month ago.

Anyone know where I get a nice shiny metal one from???

[m4drx]

mine is crackoed

[Tiger_kpt]

Yeah there are a few suppliers I know that can provide CNC machined ones. I got mine for around £20 delivered. But you can get a Greddy one for a bit more.

I reckon this must be a common problem. I always thought it weird that a cap you screw on just enough to pinch it off becomes an absolute bitch to screw off after a few miles. I reckon that the oil pressure that the engine creates causes a vacuum which in turn screws the cap in much further making it much harder to come off. That\'s my theory anyway.
Changing the cracked cap made a huge difference to the oil pressure I was getting.

[Tiger_kpt]

I\'m wondering if a simple thing like this could contribute or cause engine failure - more towards failed apex seals. Such obvious things are always overlooked.

[NurburgRob]

It might just be the two plastics sticking together under the extreme temps.  I would have thought the oil pressure would try and force out the cap?

[Tiger_kpt]

Hmmm. Yes, you\'re right. Could be!