High Pitch Hiss near brake booster?

[weatherm]

Truck is running amazing! but I have a high pitched hissing noice coming from around the brake booster. There is no fluid leaking out anywere. My friend seems to think its a vacuum leak. Anybody know where it might be coming from. My brakes kinda suck too.. I have to pump them a few times to come to a stop. Drum brakes are supposed to be bad but not that bad.

My friend checked my vacuum hose going to the brake booster and it was holding solid around 18. Would the booster have a leak somewhere?? or what.. heck I dunno.

Thanks!

71 fj40

Thanks!

 

[bsmith123]

booster

Guess who, me again?

Your friend is probably right. There's no fluid in the booster so you wouldn't see any

it has vacuum on both sided of a diaphragm and when you push the pedal atmos pressure enters on the side towards you and provides the boost by working against the vacuum on the side with the check valve

try disconnecting the hose and plugging it and seeing if the noise goes away

be careful not to crack the plastic check valve and inspect it for cracks

the hose or valve is probably the culprit


having to pump the brakes might be some other things but try that and see if the prob goes away-- post up again if you still have to pump the brakes once the leak is fixed

 

[jtoro]

X2 on bsmith123, but IMHO poor braking and hissing can also be caused by a cracked or torn booster diaphragm.

 

[FF LC FREAK]

Pumping the brakes has nothing to do with the booster. The booster simply decreases the amount of pressure you have to apply to the brake pedal. If you have to pump your brakes, you need to adjust them. Do a search on here for adjusting drum brakes. There are plenty of threads covering this in detail. Basically, adjust them until they won't turn and then back off a couple of clicks. That should get you close.

As far as the hissing sound coming from the brake booster, yes, that would indicate a vacuum leak in your booster. Replace it. Again, there are plenty of threads describing which booster will bolt into your rig - mini truck, celica, fj60, etc.

Good luck!

 

[Pighead]

Pumping the brakes has nothing to do with the booster. The booster simply decreases the amount of pressure you have to apply to the brake pedal. If you have to pump your brakes, you need to adjust them. Do a search on here for adjusting drum brakes. There are plenty of threads covering this in detail. Basically, adjust them until they won't turn and then back off a couple of clicks. That should get you close.

As far as the hissing sound coming from the brake booster, yes, that would indicate a vacuum leak in your booster. Replace it. Again, there are plenty of threads describing which booster will bolt into your rig - mini truck, celica, fj60, etc.

Good luck!

Exactly!

 

[Josie'sLandCruiser]

Hi All:

I agree with "FFF."

You can drive the truck with the vacuum hose disconnected from the brake booster - I did for at least six years. Be sure to plug the hose coming to the engine - the vacuum leak can damage the engine.

Good luck!

Alan

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Pumping the brakes has nothing to do with the booster. The booster simply decreases the amount of pressure you have to apply to the brake pedal. If you have to pump your brakes, you need to adjust them. Do a search on here for adjusting drum brakes. There are plenty of threads covering this in detail. Basically, adjust them until they won't turn and then back off a couple of clicks. That should get you close.

As far as the hissing sound coming from the brake booster, yes, that would indicate a vacuum leak in your booster. Replace it. Again, there are plenty of threads describing which booster will bolt into your rig - mini truck, celica, fj60, etc.

Good luck!

 

[grant5127]

Adjustment...

Sometimes the "HISS' is brought on because of excessive pedal travel movement..........

Is the pedal travel within spec limit?

If not, shoe adjustment will be needed......

 

[bsmith123]

hissing

Pumping the brakes could mean air in the lines or could mean someone removed the residual valve but If you want to sort out the hissing then move on

heres a test for the booster
Vacuum Brake Booster Test Procedure

some more tests starting pg 10
http://www.autoshop101.com/forms/brake05.pdf

I'd probably first fix the vacuum, then bleed the brakes, and check adjustment and then look at the residual valve if you keep having to pump after that

 

[Fuzzy Logic]

Post Whore!

Pumping the brakes could mean air in the lines or could mean someone removed the residual valve but If you want to sort out the hissing then move on

heres a test for the booster
Vacuum Brake Booster Test Procedure

some more tests starting pg 10
http://www.autoshop101.com/forms/brake05.pdf

I'd probably first fix the vacuum, then bleed the brakes, and check adjustment and then look at the residual valve if you keep having to pump after that

Why didn't you post this garbage in your first post in this thread?

 

[weatherm]

OK guys awesome. Ill try that this week. I have good vacuum going to the booster but we didn't try any of the other stuff at least I don't think so.

 

[bsmith123]

PW

Why didn't you post this garbage in your first post in this thread?

I wasn't really sure about that myself but I looked it up and it appears that I did it because my life is meaningless, I crave attention, and the excitement of a high post count means more to me than anything else

 

[bsmith123]

PW

Urban Dictionary: post whore


Oh yeah here's a link if you want to read up on it some more

 

[weatherm]

resurecting this thread.

I took apart the brake booster (because I was a idiot) and checked the diaphram. Everything is good and no rot at all. I finally did some trouble shooting last night had to take a break and fix other things and the hiss is actually coming the piston that attatches to the brake pedal. where the air goes in... there is a little dust boot that I pressed up against it to see if there was any change in the hiss.. guess what there is.

with the brake in there is no hiss... with it out there is his.

 

[FJ401971]

resurecting this thread.

I took apart the brake booster (because I was a idiot) and checked the diaphram. Everything is good and no rot at all. I finally did some trouble shooting last night had to take a break and fix other things and the hiss is actually coming the piston that attatches to the brake pedal. where the air goes in... there is a little dust boot that I pressed up against it to see if there was any change in the hiss.. guess what there is.

with the brake in there is no hiss... with it out there is his.

I am dealing with the same thing (With the pedal out, there is a hiss). Did anyone address your last post or did this string just stop? Thanks for any help.