Question for Vacuum guage install

[dcstang67]

I have installed a vac gauge for a friend of mine and the vacuum source i tapped into doesnt seem to work properly. Where should I tap into to get a proper reading for the vacuum gauge? I have searched and came up with nothing. Thanks in advance

 

[goldwing2000]

Anything directly into the intake manifold should give you a good reading. If you can't find any small lines, you can tap into the PCV or brake booster lines with the proper adapters.

 

[dcstang67]

It will read about 23 inches of vacuum but when i give it full throttle or shut off the car it stays about the same. It never goes to zero.

 

[flat_black]

You bumped into one with a check valve, that's why. I assume you used the brake booster, that being the case. I'd say use a different source, and a tee. Say, perhaps, the cruise control module source line, but I havn't looked under the hood of a 3 for a while.

 

[bbrich57]

I have installed a vac gauge for a friend of mine and the vacuum source i tapped into doesnt seem to work properly. Where should I tap into to get a proper reading for the vacuum gauge? I have searched and came up with nothing. Thanks in advance

I had the same problem until I discovered that my 3 has an untapped source right on the (plastic) intake.
Look for the two check valves mounted on the middle two runners. On the LS of those (right, as you are facing the engine from the front) there is a fitting that is capped. Pull the cap off and that will give you a direct access to the intake port.