seen similar in past now u mention tennis ball, renault 5GTt iirc, used it to seal up pipe and pass air through ;)

tyre valve in a correct size sealeable metal plate and a controllable pressurised air source is best way, bit crude but works none the less

even adapted a coolant pressure tester before now
 
God knows I was just answering the question> Allthough a garage near me has one handy bit of kit but I dont think we could afford one for the odd leak check once a year!
 
Cap off turbo hose & throttle body hose, pressurise pipework through hose feeding n75 valve. listen for leaks.
Does the smoke machine pressurise the system.
 
Jake on here used on via his business to find my boost leak. Some sort of smoke machine. Not sure how much it would cost to buy though.
 
I did mine last night and found a tiny leak that only showed after 10 psi. I used a can of lynx and hair spray to cap off the turbo elbow and TB hose respectively as they are very strong. Be sure to point cans away from you and your boonet as they become missiles if your clamps aren 't tight enough.
One thing though you need to feed the vaccum nipple of your DV with the same pressurised air otherwise your dv will leask boost after a few psi. I used a 5mm plastic tee for this. i pressurised with an old foot pump and after a minute of pumping i was up to 12 psi, no need to go higher.
A most important check for peanuts, you will find leaks with this.
 
IIRC I believe the recommended psi is around 3-5, as on some engines you can blow the seals out.

One little tip for the soapy solution is, if you use a spray can it can get to areas you may struggle with a brush?
 
Err, i can think of an easier way to find boost leaks...
Have a mate sit the car at mid revs/on boost, and squirt a mixture of washing up liquid and water on all the suspect hoses/joints. All you have to do is look for bubbles.
Cheap, quick, easy, and you can always give everything a good clean while your at it!
 
Err, i can think of an easier way to find boost leaks...
Have a mate sit the car at mid revs/on boost, and squirt a mixture of washing up liquid and water on all the suspect hoses/joints. All you have to do is look for bubbles.
Cheap, quick, easy, and you can always give everything a good clean while your at it!

Car won't boost sufficiently standing still to find most leaks.