Has anyone ever had their stock plastic oil cap blow off the valve cover?

I popped my hood this morning to see what's what, and notice the oil cap is missing, and the area around the valve cover and hood liner is covered in oil (not too bad)...maybe 1/4 quart worth. Car still has plenty of oil, don't worry.


I remember my tuner removing my oil cap to smell and make sure there is no gasoline in the oil, but I could have sworn he put it back. He's human, and I might have distracted him, but I *think* he did put it back. I went fishing for it....and found this.....(the left piece is the gasket, the right piece is just the threaded part of the cap.)


I found it tucked UNDER the harness, and under the cover of the last injector (the one closest to the firewall.) The actual "cap" I can't find. Now look at the break...it's very clean, and moreover, there are no moving parts on that side of the car...so if the cap was left off, and fell down there (towards the intake manifold) there would be nothing there to "break" it.

So I guess my question is....is this possible? Is it possible for the oil cap to blow off? I do have krankvents, so if anything, it should be sucking DOWN on the cap...just trying it figure out WTF happened.

Thanks for the help guys.

 

Strange... I think your mechanic forgot to put it on or broke it. I can see this happing to mine since I usually take a mallet to my oil cap to get it lose.

Maybe the turbo just "popped" your car's cherry.

 

Thats the thing....if he forgot to put it on, and it fell intact to the drivers side of the motor bay, there are no moving parts there. It would have either just got caught on some stuff and stayed there, or dropped out the bottom of the car. If he broke it putting it on, the threads would have still been in the valve cover threads. Maybe it happened during tuning, when he was holding a higher RPM, and the pressure just blew it the hell off. I'm gonna order a billet cap now.

 

Dave-
I had mine unscrew itself once... I didn,t put the gasket on the right way (there is a smooth side and a not-so-smooth side). You were lucky... mine dropped down behind the engine, and got wedged between the tranny and the tranny tunnel... vibrated like a Mother! Took like an hour with a bolt-retreiver thing blindly fishing for it...

A far as that break goes, looks too clean to have been blown off... I would think that the edges would be more jagged...

I think your mechanic forgot to put it back on, and it snapped when the hood closed on it (sandwiching it between the valve cover and the hood).

There would have to be a helluva lot of blow-by (as in screwed ring seal) to accomplish that much pressure, and even then, the forward krank vent should open, releasing any pressure..

John

 

Great Scott! It is possible for the oil pressure to pop off a cap that was not twisted down correctly or for oil to shoot out through the threads of an incorrectly tightened cap. Your car should be fine as this has happened to my buddy's car once before too.

Once, a Guy who changed my oil forgot to put the cap back on and left it resting on my intake manifold. Long Story short, I inspected my engine bay when I noticed smoke and found the focker still sitting on the same spot, next to a bunch of oil.

You're fine mate, so long as you didn't lose all too much oil.

 

I've never seen this but could it be boost? I'm pretty sure it will take way more that 10psi to blow it like that. but maybe crank vents is what you need.

 

I guess so. It does have all the symptoms of pressure broken plastic. One jagged spot, and smooth everywhere else. No biggie I guess, could have been worse. Hopefully this wont happen with an aluminum cap (if that's what happened.)

P.S. Can you elaborate on the gasket? I have to reinstall mine, and don't want to mess it up.

 

I have krankvents, and if anything, they should be pulling the cap down TIGHTER!

Thanks for the kind words guys, I know there is nothing wrong with my car. I just wanted to know if people have ever heard of this happening...even if it's one in a million.

Only PITA is, I'm a neat freak, and need to replace my hood liner...I can't have one that has an oil stain. Any companies make aftermarket hoodliners? I don't mind going with honda, but a Gold plated Mclaren F1 style sounds cool too.

 

The rougher side of the gasket goes down. Make sure there is no residual oil around the gasket seat either...

The fact that the threads were not in the valve cover makes me think it was left off... If it were to unscrew, that would release any pressure left to break it. Likewise if it broke, no pressure left to unscrew it. I doubt both happened at the same time.

If pressure is the issue, a billet cap will only allow it to build more, possibly resulting in major problems...

John

 

Hmm...didn't think of that. If it did blow off, the threads would still be inside. You know what, I will check the hood liner, and see if there is a gash somewhere from it slamming down on it (if it was left off...should tell me everything I need to know.)