axl911

Works much better than a homemade smoke machine or various carb cleaner, propane spray.

http://forums.pelicanparts.com/porsc...sure-test.html

I actually used a compressor and kept the air pressure at 5 psi.

Bruce SEA 993

I like!

Beats blowing up the car using starter fluid and seeing if the idle comes up.

I can see this on the flammable liquid method...good news: don't need to worry about vacuum leak...bad news: burned car to ground!

Cheers!

User 122821

I've used a similar method with an air compressor for years on turbo engines since some leaks are only present with the rubber fittings are stressed. The air supply enters after the air meter. I run less than 5 psi on NA cars and 15 psi on most of the turbo engines like my VW.

http://forums.vwvortex.com/showthrea...st-Leak-Tester

IainM

Great idea - I'm going to try this on several of my 15yr+ cars with weird intermittent idle/drive problems.

Begs a question I never found time to work out. When an engine stops, what's the natural resting position? In between cam lobes? or is there always one valve open at any angle of rotation?

I guess more to the point, will the crank ever come to rest with both inlet and exhaust valve partially open on any one cylinder?

I guess not or else this vacuum test wouldn't work.

jstyer

IainM, it's my understanding that you have to seal the exhaust pipes with tape, tennis ball, or something similar... Or else this method does not work. If the exhaust is sealed, then even if you have an exhaust valve open you'll be good to go. If an intake valve is open, you should still be ok because the exhaust valve on that same cylinder would be closed, and of course the piston rings sealing the air from entering the case.

Bill Verburg

If you have access the pro smokers are the nuts, the problem w/ 993 is that the vacuum system extends up to the HVAC controls under the dash where it's eays to forget about and difficult to see.
vram vacuum


dash vacuum