As the title says my Oil cap has popped offf on me twice. I have breather filters on both valve cover, but the first time this happened I only had one breather filter on the driver side. Do you think I may have a bad cap or something else? It's a factory cap.

 

i can't see how it pops off when it threads into the neck. i'd say it's time for a new cap/better PCV system

 

Verify your PCV valves are operational. The FSM has a procedure for such things.

 

I'm going to check the threads on the neck. Maybe thats it. The cap looks fine. In fact I usually need to remove the cap with pliers cause its so dam tight.

 

Cool thanks. I don't have the FSM, so If someone would be so kind to post the procedure. I would be greatfull. Thanks.

 

That's odd, I've heard of dip sticks shooting out, but not oil caps. There must be a tremendous force under it. Let us know what it ends up being.

 

All the threads look good so far. I think I may need to drill out the PCV on the passenger side. Still listening for any advise though.

 

Ive never had my dipstick pop out but i have had my oil cap come unscrewed several times.

I installed a Z32 Brake booster check valve between the plenum and the stock PCV check valve and all my problems went away, richened my AFR. I could do a boost leak test and hear it going past the stock PCV valve. After installing the new valve it completely stopped that, no more smoking under WOT or unscrewing my oil cap.

 

Do you have any pics of your setup? I may give that a shot.

 

Sorry i don't have any pics, its really simple though, i just replaced the stock hose with regular (3/8s ithink?) hose cut it in the middle and installed a OE Nissan 300ZX Non-turbo Brake Booster Check Valve. Problem fixed. I found the idea in this thread, its a good read you should definitely check it out

https://my350z.com/forum/forced-indu...od-w-pics.html

Here is the particular post (thanks rcdash )
https://my350z.com/forum/8554082-post162.html

And here is where i bought it
http://www.courtesyparts.com/47478-v...2_883_982_989&

 

it's a threaded cap. Pressure won't blow it out, it would have to unscrew. So if it actually came off that means it unscrewed itself. THere is no way the pressure could tear those threads and blow off that oil cap and the dipstick not come out. Also it wouldprobably dent your hood with that much pressure to cause threads to strip and blow the cap off.

 

I thought the same thing, but all i can say is it did. I guess oil on the threads and vibration aid in unscrewing it, once it gets loose its very plausible it could unscrew the rest of the way.

But one the times i literally took pliers to tighten it and the next time i checked my oil it was unscrewed. It never fell completely off but was always on the last thread or so.

 

In for results, my oil cap is hard as hell to unscrew, so my results could be teh oppisite?

 

Is there a rubber gasket around your oil cap? Clean it out with mineral spirits and reinstall it.

 

Lol on the installing an Oil cap 101, that isnt the issue here. Excess crank case pressure is, whether or not the oil cap is as tight as it can possibly get or not this should not be happening, and it will lead to other problems.

 

Do you think that by not drilling out the PCV valve on the passenger side and just putting a filter on it, It's going to screw up my crankcase pressure?

 

I’m going to have to reference this thread once I get my car back together…

 

If you don't have some sort of check valve between your plenum and valve cover you will still be dumping boost in the crankcase. Add a check valve and eliminate that problem, from there you have plenty of options as far as catch can setups and venting to the atmosphere or not etc. but first of all you have to stop the boost from getting in there.

 

The plenum is capped off. There are no hoses going from my valve covers to the intake or plenum. I just have breather filters on both the driver side and passenger side covers. The PCV is not drilled out. Should I be concerned about that?

 

If you have a vented crank case (no connection between plenum and valve cover), then leave all the ports of your valve covers open, a single breather wont be enough to vent blowby while in boost. If your going to leave the valve cover vented for ever, then I recommend you drill a hole on the valve cover. I did this with a 1/2" and put a barb on it, then put a hose from that barb to vented catch can.

Look below the oil cap: