hydrovac hissing noise when travelling at 100kmh

[jackyhonta]

-Hello fellow tsikoteers, just want some advice, my ride is a L300 Versa Van 2004 model, I was traveling along SLEX going to Calamba at around 80 to 100kmh then suddenly a hissing noise was heard below the dashboard portion where the hydrovac is located, when I lessen the speed to 60kmh, nawala naman ang ingay...and when I up my speed level to 80kmh bumalik na naman siya...but the brake system is normal, hindi naman tumigas ang brake pedals which I expect kung may problema ang hydrovac, my concern is the hissing noise.Nung pabalik na ako sa Manila, I tried traveling at 60 to 80kmh pero nawala na yung noise sa hydrovac...Is it a cause of concern or its just something to ignore, kasi bigla naman nawala ??? Ang observation ko din nung papunta ako when the hissing sound occured, it is raining...Any advice sir???thank you...

[reym]

Check mo muna mga vacuum hoses baka may leak. kung wala ....

May air leak ung brake booster mo kaya sumisipol. Maganda mapalitan mo na yan baka lumala at tumigas ng husto preno mo.