Engine vacuum : tips / tricks to find leaks and increase vacuum.

[chuzie]

Post up your vacuum knowledge folks.

What do you do to find those pesky vacuum leaks?

Any tricks to increase vacuum?

I'm running 351w EFI but this would be a great all inclusive thread for reference.

 

[PaveBronco]

I MacGyver ‘d a smoke machine out of an air tank some tubing, a regulator, cigar and a container to put it in. They do sell them and I found the info from U Tube, on how the find vacuum leaks. Worked great but did find out that there are some things that are supposed to leak, EGR and the idle control solenoid from that little cap..I know this because I changed them out and the new ones did the same thing…anyway…found my leak, cracked line, but the whole shop smelled like cigars and my clothes….

 

[spray1963]

BrakeKleen

I have used BrakeKleen for years to find vacuum leaks. Spray it around all the vacuum lines, fittings and gaskets. If you have a leak the engine will stumble when it pulls in the brakekleen.

 

[pbwcr]

What most of us have done is to open up the harness and replace all the plastic vac lines with rubber. Along the way you will find the broken plastic one that is causing the grief. Do them all and the problem goes away forever. When you find stock plastic to rubber connections make the transition with metal tubing with a dab of silicon sealant.
PaulW

 

[chuzie]

I wonder if i could rig my OBA system with a cigar but not sure how that would affect the compressor.

 

[bax]

smoke machine is best.

 

[Rustytruck]

I hook up a large diameter vacuum gauge and watch the needle while wiggling hoses and I too spray with brake-kleen since its non flammable. The vacuum guage is the most reactive tool you have. I too believe in replacing all hoses and caps at the same time saves allot of headaches.

 

[pcf_mark]

I hook up the vacuum gauge and disconnect each hose at the manifold connection one by one. When you find one connection that makes the idle smooth when you disconnect and cover the port with your finger you have the branch. The effected branch it is usually easy to follow that branch to the leak.

A leak at the manifold to head seal is more difficult and brake clean does the trick.

To boost the vacuum in your EFI make changes to the advance and fuel while monitoring. I found 16-18 degrees and ~12.8 - 13.1 AFR was max vacuum. Too lean and it would falter and have less idle vacuum.

 

[YNOTBOB2007]

Hi pcf mark and Rustytruck....where do you hook the vacuum gauge to when you are testing?

 

[pcf_mark]

Any port connected directly to the manifold or in the carb base. NOT the one on the side of the metering block if you have a Holley.

 

[Tell_Sackett]

I MacGyver ‘d a smoke machine out of an air tank some tubing, a regulator, cigar and a container to put it in. They do sell them and I found the info from U Tube, on how the find vacuum leaks. Worked great but did find out that there are some things that are supposed to leak, EGR and the idle control solenoid from that little cap..I know this because I changed them out and the new ones did the same thing…anyway…found my leak, cracked line, but the whole shop smelled like cigars and my clothes….

My dad and I made one as well. We used a mason jar with a 460 Weatherby case hung from the lid. We drilled the primer out and tapped it for a diesel glow plug. Then fill the case with mineral oil and hook the glow plug to a battery. Lots of smoke.;D Then we have a aquarium pump with air going in and a vacuum line going out at the top.

I will try to figure out how to post pics later.

 

[Steve83]

Stethoscope to find leaks:

You don't waste it, breathe it, or have to put it out, like when you spray flammable liquids on a running engine.

A vacuum gauge is among the most-useful, least-expensive, & least-utilized diagnostic tools available to an auto mechanic. Check this page for vacuum gauge instructions, but I'm sure there are many other good ones. I recommend a gauge like this:

-Clickit

Adjusting ignition timing can raise vacuum, but it won't be right unless this is:

 

[chuzie]

Ur last pic came in as a thumbnail. Can't see it