I recently bought a late model 1999 S80 T6. It has been functioning great! I love the car. However, about 4 weeks since the purchase, I am hearing a strange 'hissing' sound. The sound only comes as I release the brake. It sounds like its is coming from one of the hydraulic systems in the car.<BR>Someone mentioned it could be the ABS system.<BR>Has anyone had a similar problem. Is a repair like this covered by the warranty ( I purchased the 4 year extended volvo warranty).<P>Thanks.