# Oil cap blow by

**URL:** <https://community.cartalk.com/t/oil-cap-blow-by/196322>\
**Category:** Maintenance/Repairs\
**Created:** [September 19, 2024, 1:32am UTC](https://community.cartalk.com/t/oil-cap-blow-by/196322 "2024-09-19T01:32:39Z")\
**Posts on this page:** 7\
**Page:** 1

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**Author:** ![24jake.blazon\_191351](https://avatars.discourse-cdn.com/v4/letter/2/3bc359/32.png) [@24jake.blazon\_191351](https://community.cartalk.com/u/24jake.blazon_191351)\
**Post date:** [September 19, 2024, 1:32am UTC](https://community.cartalk.com/t/oil-cap-blow-by/196322/1 "2024-09-19T01:32:39Z")

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I drive a 2000 Nissan frontier and there is air blow by out of the oil cap is that a problem?

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**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\
**Post date:** [September 19, 2024, 2:00am UTC](https://community.cartalk.com/t/oil-cap-blow-by/196322/2 "2024-09-19T02:00:01Z")

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Yes, that is a problem. The rings are worn if a lot of blowby comes out the oil cap.

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**Author:** ![cigroller](https://avatars.discourse-cdn.com/v4/letter/c/c68b51/32.png) [@cigroller](https://community.cartalk.com/u/cigroller)\
**Post date:** [September 19, 2024, 2:01am UTC](https://community.cartalk.com/t/oil-cap-blow-by/196322/3 "2024-09-19T02:01:05Z")

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Excessive crankcase blow-by. Check your PCV system. And maybe run compression test as you rings are likely shot.

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**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\
**Post date:** [September 19, 2024, 2:36am UTC](https://community.cartalk.com/t/oil-cap-blow-by/196322/4 "2024-09-19T02:36:00Z")

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Install an oil cap, the vapors will be controlled by the positive crankcase ventilation system.

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**Author:** ![bcohen2010](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@bcohen2010](https://community.cartalk.com/u/bcohen2010)\
**Post date:** [September 19, 2024, 2:38am UTC](https://community.cartalk.com/t/oil-cap-blow-by/196322/5 "2024-09-19T02:38:48Z")

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Some engines, even when functioning properly will have a lot of “air” blowing out of the oil cap, and if you remove the oil cap while running, it will even make a lot of noise. I wouldn’t make the diagnosis of excess blow-by/worn piston rings based solely upon how much “air” (combustion gases) you feel blowing out of the oil cap when opened.

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**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\
**Post date:** [September 19, 2024, 1:12pm UTC](https://community.cartalk.com/t/oil-cap-blow-by/196322/6 "2024-09-19T13:12:48Z")

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> [@bcohen2010](#):
>
> Some engines, even when functioning properly will have a lot of “air” blowing out of the oil cap,

Really? I’m curious, where is this “a lot” of air coming from, in a normally functioning, modern engine?

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**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\
**Post date:** [September 19, 2024, 4:27pm UTC](https://community.cartalk.com/t/oil-cap-blow-by/196322/7 "2024-09-19T16:27:25Z")

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Excessive blow-by is caused by worn cylinder walls/rings in the engine, or the PCV system is restricted.

For a worn engine, this product may reduce the blow-by.

> **[Engine Restorer](https://www.restoreusa.com/)**
>
> RESTORE Engine Restorer is the only product proven to repair worn cylinders and restore compression back to near original levels.

Tester