[Franco22]

I got in my car in a rush today, started up fine, went to drive off and it felt like the brakes were on. The car wouldnt roll and had no momentum. I'm sure some of you will probably realise already that I actually had a completely flat front tire. I didnt figure this out for another few minutes when I went to check . Anyway, the point of this post is that when I put my foot on the brake it hissed at me. I've never noticed this before and assume its normal, I just want to know why?

 

[iainfm]

Hissed....like the ABS came on?

 

[Franco22]

I have not noticed it hiss when the ABS has come like over christmas on ice etc but I always have music on. Today I just pushed the brake pedal down until it felt firm, it hissed and depressed a bit further?

 

[curlygrey]

I get the same ? hissing noise when I switch the engine off and depress the brake pedal. It goes away after 2 actuations, Fluid level checked and found to be OK.

 

[Franco22]

Anyone?

 

[0of0]

It's normal - mine does it occasionally - it's related to the vacuum assisted servo

 

[davealfa11]

if it hisses constantly wid foot on brake its faulty otherwise its normal

 

[Franco22]

......and if it hisses constantly what is wrong with it?

 

[davealfa11]

servo shot

 

[zulu ferret]

Servo diaphragm needs to breathe in and out. Valve hissing?

 

[davealfa11]

Servo diaphragm needs to breathe in and out. Valve hissing?

thats with foot on /off brake
vacuum assists foot brake pressure

 

[zulu ferret]

Good read up on direct acting servos section: 5.6.4 Fundamentals of Motor Vehicle Technology?:

 

[davealfa11]

if it hisses constantly wid foot on brake its faulty otherwise its normal

......and if it hisses constantly what is wrong with it?

servo shot