suitable vacuum pressure?

[Jon K]

I am wondering what a "normal" vacuum pressure is on a M50 non-vanos. My vacuum gauge reads ~18" hg when warmed up and idling. I am trying to trace a potential vacuum leak because when i take my oil fill cap off, the idle doesn't change.

[billb]

I am wondering what a "normal" vacuum pressure is on a M50 non-vanos. My vacuum gauge reads ~18" hg when warmed up and idling. I am trying to trace a potential vacuum leak because when i take my oil fill cap off, the idle doesn't change.

It does on the M42 however. My system is tight, as I just replaced all suspect hoses/gaskets last November whem my MAF went out.

[Bill R.]

I am wondering what a "normal" vacuum pressure is on a M50 non-vanos. My vacuum gauge reads ~18" hg when warmed up and idling. I am trying to trace a potential vacuum leak because when i take my oil fill cap off, the idle doesn't change.

enough that you don't notice much change... Unplug the electrical connection to the icv and then try it..

[Russell]

Lay a thin piece of plastic like a plastic grocery bag over the oil filler while idling. it should tend to suck the plastic toward the engine. My M50 has a vacuum leak from the large crankcase venilation hose. Replaced the hose and the suction seems better. Car ran fine before and after the "fix". BTW, I sensed a very quick idle adjstment when the cap was removed. So quick i am not sure it happened.

No real answer to your question- Just a shared observation

I am wondering what a "normal" vacuum pressure is on a M50 non-vanos. My vacuum gauge reads ~18" hg when warmed up and idling. I am trying to trace a potential vacuum leak because when i take my oil fill cap off, the idle doesn't change.

[Jon K]

Lay a thin piece of plastic like a plastic grocery bag over the oil filler while idling. it should tend to suck the plastic toward the engine. My M50 has a vacuum leak from the large crankcase venilation hose. Replaced the hose and the suction seems better. Car ran fine before and after the "fix". BTW, I sensed a very quick idle adjstment when the cap was removed. So quick i am not sure it happened.

No real answer to your question- Just a shared observation

So is ~18" about right for vacuum pressure? a project DSM idles ~20 - 22"