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[Webby the Bear]

I've read lots and lots on how to build a vacuum leak smoke detesting machine as to buy a proper one is stupid money.

Some ideas that I have seen work are basically running compressed air over a smoking barbecue and running that in to the inlet. May sound mad but it does work.

However I'm a bit crap at building stuff    and I do care for simplicity. So. Why not run a piece of hose (the correct size obviously) in to the manifold where the brake servo connects, blow cigarette smoke in to it but then shove the nozzle of my blow gun in, put a rag over the nozzle so it can't escape (much) and send the smoke flying round the already smoke filled system?

Obviously blow compressed air at a slow speed....I don't want to dump 3 bar in and have the plenum shoot off in to the ceiling  (that was a joke)

What are your thoughts?

[Nick W]

I doubt you'll get enough smoke from a cigarette, but building a prototype sounds like an ideal job for a couple of winter workshop nights.

I think that 'chemical smoke' would be more successful, and would have to ask my Dad about suitable chemicals. They would have to be safe, inert, cheap and readily available. Maplins sell fog machines and the appropriate chemicals which might be a good start.

[Kevin Wood]

I'd say slim.

The problem with smoke testing is that you are going to rely on smoke leaking out of a pressurised intake to see the problem. Normally, the inlet is at a vacuum, and air leaks in. So, you're relying on the leak working in both directions from the start, which makes the test fundamentally flawed, IMHO. Many leaks are "one way".

If you want smoke, get a pellet for testing flues at a plumber's merchant. More smoke than you can shake a stick at and dirt cheap.

I think such systems are just another gadget for lazy mechanics, personally, but never used one, to be fair.

[Nick W]

Smoke pellets! You learn something every day. Put one in a large lidded tub, poke some hose through the lid and seal with duct tape, fit an adjustable nozzle, and you have an instant prototype. If it works then a more permanent setup will depend upon your tools and skills.

 With care it might work for vacuum leaks too, but I share Kevin's scepticism.

[Webby the Bear]

ok fair enough guys and thanks for the input. sadly ran overtime at the shop today  but will hopefully geta looksee next week. nowt ventured and all that 

smoke pellets lol ill look in to them. yeah nick, the premise is that the smoke is formed in a tub. then pushed through with the compressed air so simply need an inlet and an outlet as you elude to. shouldn't be that difficult even for a moron like me b

[T.m.f]

Smoke pellets from plumbers merchants or smoke matches 

[Andy H]

- Take an old pressure cooker
- drill two holes in it and fit two hose connectors to it
- connect one hose to the pressure regulator on your air compressor, start off with it set to a very low pressure (2 or 3 psi)
- connect the other hose to the item under test
- drop a lit smoke pellet into the pressure cooker & close the lid

get smoking........

PS - don't get carried away with the pressure - each doubling in pressure provides double the oxygen and your smoke pellet could burn very hot indeed.