CIS vacuum leak tests

[Url]

I am wondering how you guys use compressed air to detect vacuum leaks.. Any adapters required? What needs to be sealed of (exhaust / air box / ...) Do heat exchangers affect this as well?

What other tools / procedures do you guys use to detect vacuum leak on a CIS-based car?
I've heard smoke machines, starter fluid,...

Reason why I am asking is that I want to verify if my car (1978 SC) is vacuum leak free. I am investigating a high idle issue, it is stable at 1100 rpm at all times (cold/warm) and my idle adjustment screw is all the way in..

Thanks for the advice!

[pete3799]

Here's a good start for you
http://forums.pelicanparts.com/porsche-911-technical-forum/619058-help-have-let-car-warmup-2.html

[boyt911sc]

Pete,

Now that I'm done with my battery drain problem, I will sit down and post the procedure I've been using to easily locate vacuum/air leak/s in CIS engines. I'm putting a note (reminder) on my computer screen to deliver what I promised you last week. Thanks for the reminder.

Tony

[rtorres]

I am looking forward to this as well

[Ramathorn]

subscribed. never done this on a cis but compressed air is how i always tested for leaks on my wrx.

[john70t]

I've heard to use propane around the seals, and listen/measure the engine drop.

The most common leaks are the injector seals(tough to get out without damage when they're rock hard), the metering boot, and the evap lines.

[stlrj]

Originally Posted by Url

Reason why I am asking is that I want to verify if my car (1978 SC) is vacuum leak free. I am investigating a high idle issue, it is stable at 1100 rpm at all times (cold/warm) and my idle adjustment screw is all the way in..

Thanks for the advice!

Also, your aux air regulator may not be getting power or not closing for some reason.

Distributor advanced springs might be broken. Too much advance?

[47silver]

i used the pressure side of a shop vac.
remove the rubber boot
put it in the throttle body, seal it.
get a tennis ball and put it in the exhaust pipe.
get some kids smoke bombs.
turn on the shop vac
light the smoke bombs on the intake/suction side of the shop vac.
and you will see smoke coming out the leaks

[Url]

I'll post pics soon of the setup I am using to track down the vacuum leaks.

Still interested in other procedures though! (boyt911sc? )

[boyt911sc]

Originally Posted by Url

I'll post pics soon of the setup I am using to track down the vacuum leaks.

Still interested in other procedures though! (boyt911sc? )

I am now in the middle of collecting the pictures and start the write-up. Go ahead and post your procedure. I'll post mind later. The more technique/procedure we come up the the better. It all depends on your tools, set-up, and willingness to accept which one is for you. Let's go contribute something........

Tony

[Mike Andrew]

subbed

[rching]

subsribed!
used up 2 cans of carb cleaner so far. Oil Cap removal has almost no effect on idle.

[rching]

SubsCribed!

[Bob Kontak]

Originally Posted by 47silver

light the smoke bombs on the intake/suction side of the shop vac.
and you will see smoke coming out the leaks

More than one way to skin a cat.

Have never heard of this but what a great way to save over $1k on a smoke machine.

[Jerome74911S]

Good thread. I am suspicious of my injector seals, but the list of things to do on this car is so long that I haven't gotten to them yet.

[rching]

I'm hoping to view Tony's solution before I go out looking for smoke bombs. There's nothing left for me but to look for " where there's smoke".

[timmy2]

Here is how I tested my '78.
1. Get a bottle of leak test solution or use very soapy water to help find the leaks.
2. Remove brake booster line and connect a hose to supply compressed air regulated at 3-8 psi going into to airbox.
3. Secure latex gloves covering the air box intake for the filter, another one on the exhaust tailpipe(s) and one on the oil fil cap.
4. Turn on the air and wet the injector holes, airbox seams, airbox rubber connectors, all rubber and vacuum hoses etc. with the leak detector (bubble) solution. Watch for bubbles to be constantly generated where the air is leaking

Here is a pic of an airbox that was leaking at the seams during a bench test after using the same method described above.
http://forums.pelicanparts.com/6692499-post64.html