# 2018 Citroën DS - My oil cap disappeared **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [October 20, 2021, 8:51pm UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113 "2021-10-20T20:51:50Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Carlos48](https://avatars.discourse-cdn.com/v4/letter/c/f6c823/32.png) [@Carlos48](https://community.cartalk.com/u/Carlos48)\ **Post date:** [October 20, 2021, 8:51pm UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/1 "2021-10-20T20:51:50Z")
Not sure if oil cap fell off or blew off while driving how do I know the difference sorry if it sounds stupid ---
**Author:** ![weekend-warrior](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/weekend-warrior/32/26122_2.png) [@weekend-warrior](https://community.cartalk.com/u/weekend-warrior)\ **Post date:** [October 20, 2021, 9:00pm UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/2 "2021-10-20T21:00:56Z")
it probably was not tighten all the way and vibrated loose or someone for got to put it back on. if it blew off you have a lot bigger problems. ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [October 20, 2021, 9:23pm UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/3 "2021-10-20T21:23:14Z")
How to tell the difference ? Put the cap back on , make sure it is secure and if it comes off again you will know that you have a problem . ---
**Author:** ![weekend-warrior](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/weekend-warrior/32/26122_2.png) [@weekend-warrior](https://community.cartalk.com/u/weekend-warrior)\ **Post date:** [October 20, 2021, 9:25pm UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/4 "2021-10-20T21:25:46Z")
and check your oil level because you probably lost some. ---
**Author:** ![ok4450](https://avatars.discourse-cdn.com/v4/letter/o/e9bcb4/32.png) [@ok4450](https://community.cartalk.com/u/ok4450)\ **Post date:** [October 21, 2021, 2:30pm UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/5 "2021-10-21T14:30:29Z")
Who changed your oil? Odds are whoever did it left it loose or off. ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [October 21, 2021, 2:41pm UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/6 "2021-10-21T14:41:25Z")
On a 2018 it’s very unlikely to be anything more than a loose cap. ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/30_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [October 21, 2021, 2:52pm UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/7 "2021-10-21T14:52:58Z")
Does this Citroen’s oil cap screw onto the engine, like most (or all… ?) modern oil caps? If so, then it couldn’t have blown off or even fallen off unless someone failed to tighten it after they put it back in place. Or, as was already suggested, someone simply forgot to put it back after adding oil. ---
**Author:** ![George\_San\_Jose1](https://avatars.discourse-cdn.com/v4/letter/g/e5b9ba/32.png) [@George\_San\_Jose1](https://community.cartalk.com/u/George_San_Jose1)\ **Post date:** [October 22, 2021, 12:02am UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/8 "2021-10-22T00:02:31Z")
No experience with the C-DS, but it’s possible the crankcase is becoming over-pressurized b/c of a problem with the pcv system or whatever it is that vents the crankcase. As the engine runs some exhaust gasses get past the rings, that’s normal, and these gasses go into the crankcase (below the pistons in other words). The crankcase venting system (it’s called pcv on most cars) is what removes those gasses from the crankcase. Maybe that’s not working on your car. ---
**Author:** ![pleasedodgevan2](https://avatars.discourse-cdn.com/v4/letter/p/ad7895/32.png) [@pleasedodgevan2](https://community.cartalk.com/u/pleasedodgevan2)\ **Post date:** [October 22, 2021, 3:46am UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/9 "2021-10-22T03:46:59Z")
Look harder, it could be around somewhere under the hood. Beats paying for a new one. ---
**Author:** ![NYBo](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nybo/32/17281_2.png) [@NYBo](https://community.cartalk.com/u/NYBo)\ **Post date:** [October 22, 2021, 4:59pm UTC](https://community.cartalk.com/t/2018-citroen-ds-my-oil-cap-disappeared/180113/10 "2021-10-22T16:59:01Z")
> [@George\_San\_Jose1](#): > > No experience with the C-DS, but it’s possible the crankcase is becoming over-pressurized b/c of a problem with the pcv system or whatever it is that vents the crankcase. As the engine runs some exhaust gasses get past the rings, that’s normal, and these gasses go into the crankcase (below the pistons in other words). The crankcase venting system (it’s called pcv on most cars) is what removes those gasses from the crankcase. Maybe that’s not working on your car. Not likely in a 2018, plus the dipstick would have blown out long before a properly tightened filler cap.