Sorry Mark missread your post. Those holes behind the blower are breather holes. When water comes from them it usually indicates back pressure.
Can't remember which machine you have as you bought it second hand. If it is one with a silencer on top then remove the silencer and use a 2" hose connector to join the hoses together leaving the silencer off permanently.
It is likely this silencer is caked up with detergent etc. Removing will increase your airflow and vacuum and will only make the machine a tiny bit noisier. There are 2 silencers so you will still have the one underneath.
Whilst you have the hoses opened give everything a thorough flush through with hot water.