Pcv valve operation

[Daz1968]

Can anyone explain how the pcv valve works, I have noticed on my cooper that if I disconnect hose from tappet cover the engine stalls so I presume it is constantly drawing air from the block, is this the correct operation, it just seems strange that it draws so much air, I would have thought when idling the vacuum would close the valve and seal it,

[Ronnie]

Can anyone explain how the pcv valve works, I have noticed on my cooper that if I disconnect hose from tappet cover the engine stalls so I presume it is constantly drawing air from the block, is this the correct operation, it just seems strange that it draws so much air, I would have thought when idling the vacuum would close the valve and seal it,

Hi check this link out. > https://www.mgaguru.com/mgtech/engine/cv103.htm

[seandoyle]

Thanks for posting that,very informative.

[Daz1968]

Thanks for that, I now understand how it works and have established my inconsistent tickover was actually caused by a leak on the oil filler cap, now that is fixed it works fine,
It appears it always pulls a vacuum in crank case to prevent oil leaks and fumes, I think when I remove the hose it gives too big an air leak in the system causing it to cut out.
Hopefully all will be ok now,

[Peter Laidler]

Interesting..... The article states that the top cover has a small hole in it. I've searched in my top cover and there isn't one. I can't think of any reason for NOT having one and understand the reason why there should be one.

What size is the hole?

[Oneball]

Thanks for that, I now understand how it works and have established my inconsistent tickover was actually caused by a leak on the oil filler cap, now that is fixed it works fine,
It appears it always pulls a vacuum in crank case to prevent oil leaks and fumes, I think when I remove the hose it gives too big an air leak in the system causing it to cut out.
Hopefully all will be ok now,

There’s something wrong with your PCV, it shouldn’t cut out, you’re either missing a spring, check valve or the diaphragm is holed.

Easy test is when you remove the oil filler cap the suction should be enough to depress a rubber glove over the filler neck but not suck it in.

[Daz1968]

I also stripped the Pcv valve down, checked the internals and made sure all was free, so maybe that in combination with the leak on oil filler cap has solved it, but the phrase if it ain’t broke don’t fix it will apply for now,
The hole in the top plate is very small I don’t have anything to measure it but about 1mm I would guess

[Ronnie]

Interesting..... The article states that the top cover has a small hole in it. I've searched in my top cover and there isn't one. I can't think of any reason for NOT having one and understand the reason why there should be one.

What size is the hole?

Both types have them, also Peter they have a FV No

[Cammsjb]

JPEG image.jpeg

PCV plate with hole on my June 69 MK2 S.