Large hose from oil tank to breather - would this create a vacuum leak?

[Tidybuoy]

I've replaced all of my vacuum lines and hoses but I have not yet replaced the large hose that goes from the oil tank to the breather.

I'm just curious, if this is bad, would this be a source of air leaks. I'm wondering since this is not part of the intake system.

Thanks

[theiceman]

Actually this is THE source of vaccum leak when you take the oil cap off the tank .. so if it splits ... yeah ..

[scarceller]

I had a 75 911 and this line vented into the air box, before the CIS air meter funnel. So if it vents before the air funnel it will not be a vacuum leak source. But if it vents into the intake after the air meter (like in the 3.2L cars) then yes it can be a source of an air leak. An air leak is defined as false 'un-metered' air this means false air that is introduced after the air meter, this air is not seen by the air meter and is why it's aka: un-metered air.

[theiceman]

oh good point .. which car ?

[Alan Lindquist]

I just fixed this on my 1980 SC. Yes it is un-metered air so it will affect how the engine performs.

The "hat" on top of the motor that spans the air metering plate and the throttle inlet is called the Air Flow Sensor boot. On the back side, there are two inlets. One accepts a baffled ended hose that goes to a manifold and the other hose goes to the oil reservoir tank.

In my case, the boot was cracked at the junction where the baffled inlet pipe joins with a hose clamp, and the other hose that leads to the oil reservoir tank was cracked. So it was a new boot and a new hose for me.

Replacing these hoses is no fun. It's best done with the motor out of the car. Even a partial drop would be helpful. Reaching around the backside and working blind or with a mirror to remove hose clamps is possible, but like I said, no fun. I cheated. I have an "access port" cut into the firewall behind the rear seat insulation that allows me to work on the back side of the motor. When not in use, it's covered with a screwed down cover plate. It's come in handy, but I wouldn't recommend it to a purist.

My motor runs SO sweet now that I've tracked down the vacuum leaks. Go for it. You'll love how it turns out in the end.

[Breeang]

Access port ??

What a brilliant idea ! (Why didn't I think of that?)

Details/pictures please.

[Alan Lindquist]

Originally Posted by Breeang

Access port ??

What a brilliant idea ! (Why didn't I think of that?)

Details/pictures please.

Here's a link. Sorry that I don't have any photos with the whole port cover installed.

Firewall Access Port