I am going to try to find a "smoke in a can" type product at Home Depot or Lowes's this week-end to help find if I have a vacuum leak in my hoses. Has anyone used this method? If so, do you start at the hose from the manifold? any help appreciated.

Regards, Mark :flag :chevy

 

do u have a vaccum guage??

hook it up and just plug up lines one at a time until you notice an increase...

if theres an increase, then theres a leak in that line!!


also several people suggest using a combustable spray can (carb cleaner?) to spray around the base gasket to see if thats leaking (RPM increase... itll suck it in...) and perhaps around fittings also...

:cheers: :cheers:

 

A neat trick that I learned is this. Take a puff of a cigarette and blow it into one of your vacuum lines. This will quickly positively identify where your vacuum leak is coming from.

 

WD40 works also, it alot cheaper than carb cleaner or starter fluid... hope you find the leak

ZD

 

A bic lighter works real good for this, a little raw butane is very noticable when it gets sucked in. I will disavow any responsibilty for this tip.

 

I use Propane and a long small diameter hose. I promise it won't explode... just don't drop the tank into the fan blade. :eek:

 

Mark,
If you own a Vette, work on it and plan on keeping it, put your money towards a vac gauge instead of the "smoke in a can" stuff because if your going to go through the time and effort to start to track down the vac leak , then you may as well have some concrete data to verify the tubing condition as being either good or bad. Thus simplifiying your efforts in the end and not leave you with a needle in the hay stack approach. A vac gauge will do that for you. Last thing you want to do is start blowin' alot of smoke and miss the leak because its windy or you can't see where it is coming from.
Your best bet would be to buy a vac pump, which has a gauge on it to allow you to create your own vacuum and see if the section of tubing you are testing will hold the vacuum for a few seconds. Obviously the opposite end of the piece of tubing you are testing must be plugged. If it does, then that concretely verifies that that peice of tubing is not leaking. If it does not hold the vacuum you put to it,then it is bad and should be replaced. If that section of tubing is good, then move to the next peice of tubing, following the trail of vac tubing from the manifold through the firewall to undr the dash, then back out the firewall onto the front of car to the head light vac relays and actuators. Because there is so much vac tubing and many systems in a Vette, a vac pump, in my opinion is a must have tool to allow you to maintain and repair these systems. There are basically two variations of the same Mighty Vac Pump which are made. A plastic housing pump and a metal housing pump. I purchased the metal pump for $55 at a swap meet in a nice case which included a great set of instructions that explained other uses for the pump. The plastic housing models are like $20-30 cheaper, but could be easily broken if they fall or if the seal becomes gummed up to the point where you squeeze the handle so hard to break it free that it can get broken.
You can also use a vac pump to help suck the air out of the your brake lines. I love to use the gauge on my pump to help me set the idle mixture screws on a carbs that I am trying to set up. Most guys just use the idle by ear method, but I like to be able to concretely know that the idle is set right. In that instance all you do is turn the idle mixture screws in and out until the engine produces the most vacuum. When it does, you have the mixture screws set correctly, provided they each are turned out approximately the same amount of turns. This works because you have adjusted the engine to operate as effieciently as possible which it makes the most vacuum when it is doing so.
I realize that this may not be the direction or answer you were looking for, but I wanted to make sure you were seeing the big picture and aware of how easily you can verify the condition of your vac tubing with this wonderful device.
Boy do vac. leaks ever suck ( in fresh air)
"TEACH"

 

Why do you think there is a leak? At certain temperatures and certain year vettes with certain engines there is supposed to be a leak in the distributor, and/or EGR, and/or smog pump vacuum systems. Your problem could be a thermal switch stuck open or something if there is a vacuum leak all the time.

Uh, when I've taken my other car to get smogged and the smog place sprays carb cleaner around I have to replace my vacuum hoses cause they get brittle and start to leak for sure. Any fuel like:

or

will make the hose swell, become brittle, and CAUSE a leak. Of course shawn comes through with:

which would work, but then you will die of lung cancer, or be like my dad and not die from it leaving you unable to breath well enough to take a shower (he has to rest for an hour after taking a shower to catch his breath). Maybe some ganga smoke would work better cause it's thicker and more expensive, and if you have to die it will be with a wide grin on your face!

Actually, ZD75blue says
which will work OK and not hurt the hoses.

What I do is make a diagram of the entire system, then dismantle the system and check each hose and device seperately, comparing it to tests and functional descriptions in auto repair manuals. My leaks have always been from Bubba connecting the system up wrong, and I think once it was due to a stuck TCS, and another to a stuck EGR. I also clip the ends of the hoses to get some fresh hose on the connectors, or bought new hoses. If your engine has backfired a few times then it may just be brittle hose ends.


[Modified by Rockn-Roll, 5:50 PM 12/7/2001]

 

I used a mighty vac to check my system and the hoses were good for the most part. My leaks turned out to be the vacuum relays. Which you can also check with the vacuum gauge. Also you can put a lot of vacuum on the tank and listen for the leaks.

 

I tried the flammable route for the base of the carb and had no luck, it sucked it in anyway.
On a boat board, under the most embarrassing things you've done. One guy tried this method on his outboard, he didn't take the cowling off. Can you say
boom. This was starting fluid in an attempt to start it.

 

:lol: :lol: :lol:

 

Great stuff guys!

Teach, that is an awesome explanation. Thank you very much! I do have a Vac. gauge,but no pump. I'll try it with the motor running to at least check the manifold line. I just wasn't sure about the procedure to follow. Now I know.

Rock n Roll, I get an unsteady idle, in that both the rpm and vacumm goes up and down constantly at idle. Approx. 1 to 2 lbs of vac. and 100 to 150 rpm's is the variance.

Thanks again to everyone for their help!

Regards, Mark

:flag :chevy