Smoke test

[mark houghton]

...or more appropriately vacuum leak test.
Hey kids, been a while since I've posted anything. Trying to find informative info on how to perform a smoke test. Our host has a generic tech article for 911's but not specific to 930's...and I seem to be coming up empty handed on searches.
Point me in the right direction or just give a few general directions on how you've done it....with and without IC removed. Save me a bunch of time trying to re-invent the wheel so to speak, before I purchase a smoke generator.

[Alan L]

Mark, I bypass the smoke test - and use about 5psi pressure - from the intake elbow.
Works well. Can't put too much pressure on the elbow - soft rubber - not made for pressure. But 5 psi is plenty to find any leaks - it will come (p)hissing out.
Just a piece of plastic plumbing fitting that can squeeze in to the elbow, with a cap on it and a threaded hose nipple.
Alan

[Bucketlist]

Here's the new and the old:
I bought a smoke generator off ebay and hooked it up to my intercooler idle air feed. Attached the leads to my battery, hose to compressor and added maybe 2-3#. After it started generating smoke it took only a minute or two to expose my air leak where I had pinched an o-ring between the turbo and up-pipe. I thought that connection was good and was looking for something else.
Back in the day we would take a long drag from a cigar and blow it into a vacuum line or something and it usually worked.

[GregPV]

I went the same route as Alan but used a hockey puck wrapped some electrical tape around it to fit snug drilled a hole in the top added a fitting. Can make a redneck smoker if you have a compressor using a glass jar with lid drill holes in lid add two fittings one to blow in one to exit and soak an old sock in baby oil put in jar light with lighter get it smoking put lid on your set. Good luck.

[mark houghton]

Thanks guys. I figured it was a simple operation all in all, smoke or not, but do like the diy redneck smoker and particularly firing up a good cigar as a diagnostic tool.

[gary23]

Originally Posted by mark houghton

...or more appropriately vacuum leak test.
Hey kids, been a while since I've posted anything. Trying to find informative info on how to perform a smoke test. Our host has a generic tech article for 911's but not specific to 930's...and I seem to be coming up empty handed on searches.
Point me in the right direction or just give a few general directions on how you've done it....with and without IC removed. Save me a bunch of time trying to re-invent the wheel so to speak, before I purchase a smoke generator.

Good

[mark houghton]

Took Alan's method and rigged it up. Can hear air escaping somewhere behind and to the left of the IC. Squirted soapy water wherever I could reach, to no avail. Can't see or reach crap with my larger B&B IC in the way. So I'm gonna rig up a smoke jar per Greg's suggestion and have a go at it again tomorrow. Just need to narrow it down to the general area then pull off the IC and poke around.
The best way would be to pull off the IC and rig some plumbing/hose from the turbo up pipe over to the throttle body...challenging finding the material to do that.

[pkabush]

There’s a pretty informative YouTube video from a guy doing it on a SC
It drags on a bit but it’s pretty thorough.
I like Allan’s method though. Much easier and cheaper.
Maybe you can pull the innercooler and cap the openings. That would take everything else out of the equation as long it holds air.

[mark houghton]

Originally Posted by pkabush

There’s a pretty informative YouTube video from a guy doing it on a SC
It drags on a bit but it’s pretty thorough.
I like Allan’s method though. Much easier and cheaper.
Maybe you can pull the innercooler and cap the openings. That would take everything else out of the equation as long it holds air.

If IC pulled then won't be able pressurize the intake manifold and thus all the various vacuum lines etc. Would have to bridge the connection from the turbo compressor outlet to the throttle body. I once saw a picture of someone who did that with a flexible hose of the correct diameter...gotta be 2.5" or so to fit the TB and turbo. Or perhaps I can MacGiver some caps/plugs and run a smaller diameter hose between them. I'll figure something out, guaranteed.

[mark houghton]

This may turn out to be one of those epic waste your time postings, but my time is free and yours is to do what you wish with it.
Rigged up a smoke jar: oil soaked rag, wrapped with nichrome wire and hooked to a battery charger. Nice copious and continuous smoke. Tried just lighting the rag on fire first but smoke was short lived.

Hooked her up to the air compressor, saw one tiny leak from a vacuum line that had been plugged off with tape (ugh), but after a couple minutes had smoke drifting everywhere up from the muffler tip and wastegate muffler. Guess I pretty much filled the entire intake, heads and exhaust manifold with smoke!

Next to pull the IC, plug the TB opening and compressor outlet, run a hose between the two, rinse and repeat.

[Alan L]

Mark - you da man.
Maybe the hard to find leak is in the CSV (PITA to get to) or the back side of injector blocks.
Good luck. When you find it you will be better off.
Regards
Alan

[mark houghton]

I did remove the IC and rigged plugs for the turbo up-pipe and boost recirculation manifold to the throttle body and connected both with a length of hose. With the damn recirculation manifold in place its difficult to see exactly where leaks are coming from. Appears to be in the general location of where the recirculation manifold mates with the TB...possible bad o'ring. I think a good winter project. The car is running fine in all regards EXCEPT for closed throttle in gear coasting to a stop...she'll start bucking once rpms drop to 950. Full vacuum with TB butterfly closed, may be sucking in some air from a bad o'ring or other as yet unknown location.

[macronbill]

The videos are all over Youtube. You should make some research on that.

[jonesb930]

Mark,

I tried making one from PVC fittings like some of the YouTube videos show. It worked just enough to make me realize that I really need one of these. Then it failed, then leaked and made a mess. So, I started to search for a proper solution. There is a pro one that is over $1000 that is nice, but a bit unnecessary for me. I ended up with one off of Amazon that is made from automotive paint gun parts. It was around $120 but quite easy to use and setup. It came with everything you needed. I had a slight issue with the heater coil, and they sent me out a full replacement element at no charge. This unit helped me chase down many small vacuum/boost leaks on my son's WRX. I also ordered an additional item that I will link below

Here is a link to the smoke machine: https://amzn.to/3KOZRga

I also ordered one of these to better block off the intake pipe while giving me a port to plug the smoke machine into. I was using plasic lids and tape but found it would leak smoke and make it more difficult to see where it was coming from.
https://amzn.to/44dujr3

[1Bad86]

I have the same smoke machine as in the provided link.
It has worked great by providing locations of leaks and tears from me.
My current project has had a looonnnggg list of set backs from "Easy Straightforward" updates.

[turbo ride]

if you use a stethoscope with a tube on the end (automotive stethoscope?) you just pass the end by any junction and along the hoses and if there is a leak you will know as it hisses loudly in your ear.

Brandon
'91 964 Turbo

Originally Posted by mark houghton

Took Alan's method and rigged it up. Can hear air escaping somewhere behind and to the left of the IC. Squirted soapy water wherever I could reach, to no avail. Can't see or reach crap with my larger B&B IC in the way. So I'm gonna rig up a smoke jar per Greg's suggestion and have a go at it again tomorrow. Just need to narrow it down to the general area then pull off the IC and poke around.
The best way would be to pull off the IC and rig some plumbing/hose from the turbo up pipe over to the throttle body...challenging finding the material to do that.

[mark houghton]

Originally Posted by turbo ride

if you use a stethoscope with a tube on the end (automotive stethoscope?) you just pass the end by any junction and along the hoses and if there is a leak you will know as it hisses loudly in your ear.

Brandon
'91 964 Turbo

Good idea. This winter I will check again and try this method. I just happen to have a medical stethoscope that I could modify appropriately.