***WARNING*** I am not certain of the effects of acetone on housing materials.
The way to find a vacuum leak is to draw a vacuum on the vessel, then while monitoring the vacuum level spritz acetone around the seals and fittings. The acetone will work like the soapy water mixture does on pressure vessels as a leak spotter. It will get drawn in through any leak and rapidly evaporate under the vacuum, thus causing a quick jump up on the vacuum gauge. Alcohol may be able to be used in place of acetone, but I am not sure if it would evaporate fast enough to make a noticable movement in the vacuum gauge.