In the process of troubleshooting my brakes I hooked a vacuum gauge up to my intake manifold to check the vacuum. When the engine is warmed up I am pulling ~12 inHG. According to the Haynes manual for every 1000ft above 2000ft you can add ~1 inHG to the reading, so now consider that I am at ~4500ft elevation that would indicate ~14.5 inHG vacuum. Haynes also says a normal and healthy engine should pull around 17-22 inHG. Should I be very conserned?

I'd like to try to find any vacuum leaks, if thats the problem. Does anybody have any tips on how to find them short of just replacing/tightening stuff? It's not like I can just spray soapy water and look for bubbles since we're talking vacuum right?

Also what effect would this low vaccum have on the brakes?

Any insight would be greatly appreciated.

I don't know what the vacuum should be in your vehicle, but assuming that the manual is correct, your thoughts and the other posts will put you on track to find a vacuum leak. However, before you start, there is something you should understand about manifold vacuum.

A vacuum leak can affect manifold vacuum, but not directly, in the way you might think.

Strong intake manifold vacuum is an indication that your idle mixture is near optimum (the word I am groping for here starts with stoi.... but I can't spell it) on all cylinders.

If your rpm is not limited by an over-rich or over-lean condition, or by uneven operation of cylinders, then the only thing limiting your rpm is the throttle plate, and the engine will pull a strong vacuum behind the throttle plate.

A vacuum leak will result in low manifold vacuum, not because it is simply leaking in air, but because it messes up the air fuel mixture and the uniform operation of your cylinders. That causes your engine to develop less power, so it barely keeps running at idle RPM. The throttle plate sees less 'pull' as it restrains your engine to idle RPM, and hence, less manifold vacuum is measured.

Incorrect timing at idle, or even an obstructed exhaust, can also reduce your manifold vacuum. Anything that restrains your engine at idle will show up as reduced manifold vacuum.

The brakes probably aren't an issue. There's a check valve in the line to the booster and it has a pretty large capacity.

The usual way to find vacuum leaks is to spray a solvent or flammable aerosol on suspect areas- all around the intake manifold gasket, and the injector seals, usually. The idle will go up noticeably if there is a leak- the engine pulls in the solvent and burns it, just like a shot of extra fuel.

Carburetor cleaner works, as well as WD40 or 3/36 type products. Pretty much any spray with "flammable" or "combustible" on it will do fine. Avoid spraying the distributor as well as any painted surfaces as much as possible. Eye protection is ALWAYS a requirement.
Good luck!
--
Rob Bareiss, New London CT ::: "Roterande Fläkt Och Drivremmar!"