Oil Cap Coming Undone When Driving

[sideshowfred]

A couple of weeks ago on my way home from work the car suddenly got really sluggish, with a lumpy idle and no power. I crawled it the 2 miles home and found the oil cap was loose and had come out of it's hole. I've been keeping an eye on it and over the course of a few days it's slowly undoing itself again. I have noticed the white mayo type stuff that is on the bottom of it which is due to my short journey's I believe, (2 miles to work 4 days a week), but i've been cleaning this off every few days. But even on a 40 mile run at the weekend the oil cap still moved round about 30 degrees.

I've had a quick look and couldn't see any similar posts so can anyone tell me what's going on? And how to maybe fix it? Or should I try a new oil cap?
Any help appreciated as it's really doing my head in now.

Cheers
Fred 

[RedRobin]

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Crikey! My oil cap locks on so hard that I usually need two hands and lots of strength to undo it!

Something definitely wrong with yours. Have you closely inspected both the cap and the neck it fits onto? Seals?

[GTI5]

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Crikey! My oil cap locks on so hard that I usually need two hands and lots of strength to undo it!

Something definitely wrong with yours. Have you closely inspected both the cap and the neck it fits onto? Seals?

x2 Thats how I broke my OEM cap...the top came away on a crisp morning

The only thing I can think is the thread is worn?

[bacillus]

I would try a new oil cap but deep down I'm wondering if your pcv could be faulty.

[camfollower]

I had this happen in the summer. Carry a spare in the glovebox now, just in case.
Supposedly it's the engine cover moving and prising off the oil cap during heavy accel / decel. 

[RedRobin]

Supposedly it's the engine cover moving and prising off the oil cap during heavy accel / decel. 

....That's highly likely - On stock engine mounts the 2.0T FSI moves a lot and has even broken this metal mounting point on some cars:

[sideshowfred]

Cheers for the quick responses guys, they're much appreciated. I'll have a look at the cap and neck before I go to work in the morning. With regards to the engine cover moving, would I still need a new cap? Or is it down to something else that needs to be fixed/replaced?

I suppose i'd better search how to check for a faulty pcv and see if that's broken. Wouldn't be so bad but one of my lambda sensors has gone aswell (according to the light on the dash at any rate). Don't spose that could be linked could it?

[camfollower]

Cheers for the quick responses guys, they're much appreciated. I'll have a look at the cap and neck before I go to work in the morning. With regards to the engine cover moving, would I still need a new cap? Or is it down to something else that needs to be fixed/replaced?

Check the engine cover mounts and rubber bungs... time allowing, take the engine cover off and make sure all the mounts are screwed in tight, placing a small amount of grease on the bungs for easier removal next time.

If you haven't removed the cover before, make sure NOT to put pulling pressure on the bottom as it could snap.  Like most things, once you've done it a couple of times, it's easy.

Remove the induction pipe from the Engine Cover / Air box (bottom right), then unclip the engine cover from near the MAF housing (top left), there's a top and bottom of the clip, pull the outlet of the MAF housing left, away from the engine cover, then pull the top right on the engine cover upwards and left, essentially prising the cover from the mounts... this I've found is the best way.

Since I made sure all the mounts were on and tightened my oil cap top hasn't seperated, worth checking mate.

[sideshowfred]

Well, checked my engine cover before heading to work and it wasn't actually connected on the front!! Anyway, took my lunch break to whip it off and see what had happened. I found that on the lefthand side of the engine the bracket was completely loose. And on the right hand side that this had happened to the bit the bung sits on.


IMG439 by sideshowfred1990, on Flickr

Needless to say there wasn't alot I could do about this bit today. I tried tightening up the bolt on the other bracket but couldn't get the star key I was using seated properly as, what I assume is the inlet manifold, was in the way. 

As such the engine cover is still loose. But i've decided that instead of replacing the standard airbox, (as it turns out half the screws that hole it together are broken), i may as well buy an induction kit and bypass this problem all together.

Thanks for your help guys, made me more confident on how to sort this little niggle out

 

[RedRobin]

^^^^
That's good news! 

I've always thought that the OEM engine cover design was bad. and cosmetically, that dirty grey fake aluminium centre strip is horrendous, IMO.

[sideshowfred]

I agree that it's a stupid design. I painted the grey bit blue so it didn't look too bad until i could warrant getting a proper induction kit. So in a way i'm quite happy that it's the simpler and better solution 

[GrayMK5GTI]

Is that the engine mount that's broken? 

[bacillus]

Is that the engine mount that's broken? 

No, it's one of the 4 pegs that the grommet for the engine cover locks on to that broken.

[RedRobin]

No, it's one of the 4 pegs that the grommet for the engine cover locks on to that broken.

....A very common breakage due to the trickiness of removing the OEM engine cover/filter box.