Oil Breather Cap

Eman1019 · Apr 24, 2017

I ordered a chrome breather cap to replace the stock oil fill cap for the looks alone. Seems to be a debate over whether or not I need to do anything other than screw it in. I have a fairly stock engine except for CAI, tri-y headers, custom exhaust.

Am I going to get stuck on the side of the road???

mikestang63 · Apr 24, 2017

if it is an open breather style cap send it back as you will be sucking in unmetered air.

jrp27540 · Apr 25, 2017

Wouldn't it only allow unmetered air if he ran the PCV valve on the other side? If I understood my research on this topic correctly, you dont want to run a breather cap AND the PCV valve at the same time; If you ran breather caps on both valve covers, then no unmetered air will be pulled through the breather cap and back into the intake via the PCV valve. If I understood it all correctly, if you cap the vacuum hose port on the throttle body, cap the PCV vacuum port on the intake and run two breather caps, then you would be OK. Let me know if i'm wrong....

Mustang5L5 · Apr 25, 2017

jrp27540 said:
Wouldn't it only allow unmetered air if he ran the PCV valve on the other side? If I understood my research on this topic correctly, you dont want to run a breather cap AND the PCV valve at the same time; If you ran breather caps on both valve covers, then no unmetered air will be pulled through the breather cap and back into the intake via the PCV valve. If I understood it all correctly, if you cap the vacuum hose port on the throttle body, cap the PCV vacuum port on the intake and run two breather caps, then you would be OK. Let me know if i'm wrong....

EFI engines don't have breather caps on both valve covers. Just the single oil fill port, with a vac line from the throttle body to the fill port.

When you put a breather on the oil fill port, the engine sucks air from the throttle body tube from the breather.

jrp27540 · Apr 25, 2017

Mustang5L5 said:
EFI engines don't have breather caps on both valve covers. Just the single oil fill port, with a vac line from the throttle body to the fill port.

When you put a breather on the oil fill port, the engine sucks air from the throttle body tube from the breather.

Yes, that makes sense. Thanks for the clarification.

Eman1019 · Jul 9, 2017

I plugged it up with some high temp silicone and kept the look without affecting the engine function.

Oil Breather Cap

Eman1019

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mikestang63

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That is…until I whipped out my Bissell

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