Vacuum leak - smoke test: 83 SC

[83_Silberpfeil]

Getting ready to do a smoke test to identify any vacuum leak. 1983 SC USA model, with heater blower in place, and also has cruise control. Have a few questions below:

1) Where to introduce smoke into the intake - most convenient location? I saw the "Joe Engineer" youtube video. He connected smoke into where the brake booster line draws vacuum from engine. Since I have heater blower/motor in place, accessing the brake booster vacuum line not very convenient. Any alternatives --- I recall reading about using the cruise control vacuum?

2) Must I remove the intake rubber boot, and plug the two hoses and cover the TB? Is there any way around this? Access to remove/replace the boot is not easy.

3) Any other areas that needs to be plug'd or removed?

I put together a DIY smoke generator at a cost of less than $20. Tested it, and it generates loads of smoke. I'll be using an FB foot pump (for bikes and balls) to move the smoke into the engine. Think I need to add more baby oil to the wick and reservoir underneath.

Thanks!
Jonathan

[Johner]

1) once I had the test set up I tried introducing smoke in a few places to test the whole system I think I used a WUR vacuum line (befire the thermovalve) and a distributor line. I don't have the same CIS as you but you could find similar test.points

2) Last time I did this I tried to make sure I tested as much of the system as possible, so lifted the rubber boot and blocked off the sensor plate end with a bit of plastic bag secured between the boot and the sensor plate body with the band clamp. I think I had to block off the line going to the oil tank from the boot. I did a partial engine.drop to make it easier to lift the boot, but might not be necessary.

3) If you have a pop off valve you probably need to put some weight on it.

You might find your set up needs a reservoir of some sort to keep a constant supply of air whilst you looked for leaks. The first time I did this I used a garden sprayer as a source which worked ok, but next time I borrowed a neighbour's compressor which made it much more effective.

John

[boyt911sc]

Jonathan,

There are several spots you could inject smoke into your CIS to locate these hard to find air leak sources, namely:

• Brake booster vacuum tube by the side of the air box.
• POV
• Any of the six (6) fuel injectors mount. Remove the injector and use the hole.
• Any of the vacuum lines on your motor.
• Oil tank.
• Throttle body.
• Etc.

The key is to isolate the air box from atmosphere and your smoke test would be very effective. You only need less than 2 psi. of air pressure to create a positive pressure in the system. Lastly, you need to remove the CIS boot between AFM and throttle body. No need to plug the exhaust pipe to find the leaks. I’ve been doing this test successfully for many years without blocking the exhaust pipe.

If you correctly isolated the air box from atmosphere, it would only take a couple of seconds to do the test. You need a continuous supply of low pressured air for this test and create a positive air pressure with smoke to locate the culprit/s.

Tony

[PeteKz]

Business opportunity: Smoke in a spray can. It would have a little different nozzle than a typical spray nozzle. It would have an adapter to fit a vacuum hose, maybe something like the tops of cans of insulating foam. Then just hook it up to a vacuum hose on the engine, press the top/valve and you have instant smoke for testing.

[EC900]

I just seen on a home repair show that ‘Smoke in a can’ was used to check operation of newly installed smoke detectors, online price ranges $10 to $20 a can. Convenient enough for a one or two time use if you can’t DYI a smoke generator. Using this method for engines, I wonder how much you can spray would be needed to find results. Maybe even the spray nozzle can be swapped for one that can accept a pinpoint straw.

[PeteKz]

I've seen those at Home Depot, but if I understand correctly, they don't make a lot of visible smoke, just a type of smoke that tests the detector.

"Smoke in a can" would be faster and more convenient than setting up a smoke generator, so it might be useful for commercial shops too, based on time savings.

I saw something else that might work too: "Moccasin Joe Smoke in a Bottle." It s used for determining wind direction for hunters. But I think it s a very fine dust, rather than smoke.

[83_Silberpfeil]

@Johner - thanks for advising and sharing your past experience w smoke testing.

In reply to your comments to my Qs:

1) I will check the WUR lines and see where they attach and determine if easily reachable.

2) "lifted the rubber boot" --- does this mean just loosening the boot clamp and lift it a bit, not completely removing? Interesting idea that I will look into. The hard part for me is removing the hose connections at back (by the firewall) of the rubber boot --- extremely hard to reach/access.

3) No pop-off valve modification in my airbox.

"reservoir" - My idea is to use a foot pump from Harbor Freight (intended for bike tire or soccer balls) to keep the air flow generate pressure. No idea if that will work , or if sufficient flow or pressure. May end up buying a small aquarium air generator pump from amazon ~ $20.

Originally Posted by Johner

1) once I had the test set up I tried introducing smoke in a few places to test the whole system I think I used a WUR vacuum line (befire the thermovalve) and a distributor line. I don't have the same CIS as you but you could find similar test.points

2) Last time I did this I tried to make sure I tested as much of the system as possible, so lifted the rubber boot and blocked off the sensor plate end with a bit of plastic bag secured between the boot and the sensor plate body with the band clamp. I think I had to block off the line going to the oil tank from the boot. I did a partial engine.drop to make it easier to lift the boot, but might not be necessary.

3) If you have a pop off valve you probably need to put some weight on it.

You might find your set up needs a reservoir of some sort to keep a constant supply of air whilst you looked for leaks. The first time I did this I used a garden sprayer as a source which worked ok, but next time I borrowed a neighbour's compressor which made it much more effective.

John

[83_Silberpfeil]

Thanks for chiming in Tony. BB vacuum tube has been a common suggestion. I'll see if I can reach it easily with the heater blower and cruise control bits in the way. I think I'll invest in a $20 air pump (for small aquariums) to push the smoke and create positive air pressure.

Added comment: I found an old AC plug-in air pump for inflate-ables. It generates up to 0.49 psi. Will this be adequate, or too low pressure?

Originally Posted by boyt911sc

Jonathan,

There are several spots you could inject smoke into your CIS to locate these hard to find air leak sources, namely:

• Brake booster vacuum tube by the side of the air box.
• POV
• Any of the six (6) fuel injectors mount. Remove the injector and use the hole.
• Any of the vacuum lines on your motor.
• Oil tank.
• Throttle body.
• Etc.

The key is to isolate the air box from atmosphere and your smoke test would be very effective. You only need less than 2 psi. of air pressure to create a positive pressure in the system. Lastly, you need to remove the CIS boot between AFM and throttle body. No need to plug the exhaust pipe to find the leaks. I’ve been doing this test successfully for many years without blocking the exhaust pipe.

If you correctly isolated the air box from atmosphere, it would only take a couple of seconds to do the test. You need a continuous supply of low pressured air for this test and create a positive air pressure with smoke to locate the culprit/s.

Tony

[83_Silberpfeil]

Smoke in a can --- interesting idea. Visible smoke is critical in our automotive application.

Originally Posted by PeteKz

Business opportunity: Smoke in a spray can. It would have a little different nozzle than a typical spray nozzle. It would have an adapter to fit a vacuum hose, maybe something like the tops of cans of insulating foam. Then just hook it up to a vacuum hose on the engine, press the top/valve and you have instant smoke for testing.

Originally Posted by EC900

I just seen on a home repair show that ‘Smoke in a can’ was used to check operation of newly installed smoke detectors, online price ranges $10 to $20 a can. Convenient enough for a one or two time use if you can’t DYI a smoke generator. Using this method for engines, I wonder how much you can spray would be needed to find results. Maybe even the spray nozzle can be swapped for one that can accept a pinpoint straw.

Originally Posted by PeteKz

I've seen those at Home Depot, but if I understand correctly, they don't make a lot of visible smoke, just a type of smoke that tests the detector.

"Smoke in a can" would be faster and more convenient than setting up a smoke generator, so it might be useful for commercial shops too, based on time savings.

I saw something else that might work too: "Moccasin Joe Smoke in a Bottle." It s used for determining wind direction for hunters. But I think it s a very fine dust, rather than smoke.

[boyt911sc]

Originally Posted by 83_Silberpfeil

Thanks for chiming in Tony. BB vacuum tube has been a common suggestion. I'll see if I can reach it easily with the heater blower and cruise control bits in the way. I think I'll invest in a $20 air pump (for small aquariums) to push the smoke and create positive air pressure.

Added comment: I found an old AC plug-in air pump for inflate-ables. It generates up to 0.49 psi. Will this be adequate, or too low pressure?

Jonathan,

If you have a battery operated tire pump, it is more than sufficient. I just run the pump several seconds to build air pressure inside the gallon paint can and turned it off. A foot pump or bicycle pump would also work. Air mattress air pump or air bellows are also OK. Test and practice using your smoke generator.

Tony

[83_Silberpfeil]

I will try with my plug-in air pump for air mattresses and pool-side inflate-ables. Hopefully I can remove the intake rubber boot connections by the back firewall w/o much struggle.

Originally Posted by boyt911sc

Jonathan,

If you have a battery operated tire pump, it is more than sufficient. I just run the pump a several seconds to build air pressure inside the gallon paint can and turned it off. A foot pump or bicycle pump would also work. Air mattress air pump or air bellows are also OK. Test and practice using your smoke generator.

Tony