Power Brake booster Vaccuum Leak at Pedal

[chevyaddict]

Hi All;
I haven't gotten in there yet but I have no power brakes due to a massive vacuum leak at the pedal. You can hear it - it is substantial. My question is, do you think I can just replace the boot itself or is it more likely the diaphragm in the brake booster is broke around the area the pedal depresses into the booster? I'm not sure how these things are engineered and only guessing. I'm frankly surprised I don't have engine-running problems with the amount of vacuum leak. Was hoping the fix might be more simple than having to replace the whole booster.

 

[gmjunkie]

Hi All;
I haven't gotten in there yet but I have no power brakes due to a massive vacuum leak at the pedal. You can hear it - it is substantial. My question is, do you think I can just replace the boot itself or is it more likely the diaphragm in the brake booster is broke around the area the pedal depresses into the booster? I'm not sure how these things are engineered and only guessing. I'm frankly surprised I don't have engine-running problems with the amount of vacuum leak. Was hoping the fix might be more simple than having to replace the whole booster.

If the booster is leaking,You should be having a Idle issue or surge in engine rpm's!(Unstable idle,surging or maybe even some intermittent misfire!) Have you checked the vacuum Dump switch/s and hoses on the brake peddle? They'll sometimes crack or break, they'll sometimes sound like allot worse leak than there is and not affect the engine at all!~!

If it's the booster,Replace it!

Good luck with it Dawn!~!!!

 

[chevyaddict]

Ya know, that is what I thought. It sounds like a MASSIVE leak, and my brakes are hard as a rock... because of both of those the booster itself must not be keeping vacuum correct? But I am not having any idle issues or car surging issues whatsoever.....

 

[boomdriver]

Either way,. the booster has to come out.

There is a small chance that the line to the booster is bad, or the check valve. Not likely.
If there is a hard pedal, hissing (air leak, vac) and the line to the booster is ok, the booster is blown. They can be a major PITA to repair because there is a BIG ugly spring inside that tends to jump out when you open the case....hurts too.

so, a reman exchange is what most folks do. You can do that with or without a master cyl attached...its about $350 with both. $150 to $200 for just the booster. You'll need a little person too...half the work is under the dash on the brake pedal wayyyy up there where you can;t see or get your hands.

 

[chevyaddict]

You'll need a little person too...half the work is under the dash on the brake pedal wayyyy up there where you can;t see or get your hands.

Yes, thankfully I am a little person. This is actually what I'm NOT looking forward to - especially with an L5/S1 herniation. I have a feeling having my back arched over the door sill area is gonna be AWFUL. Thankfully I can get a reman of the booster at autozone for $102 so not too bad. It gradually got worse over the course of about a month to where now I have no boost at all. Makes braking a little challenging and I know this is hard on the master cylinder so it just needs to get done. Oiy.

Thanks all for the input! I'm still baffled though at the lack of it NOT affecting how the engine is running..........

 

[gmjunkie]

Thanks all for the input! I'm still baffled though at the lack of it NOT affecting how the engine is running..........

Every booster will go bad a little different than the next!

Take the drivers seat out,fold up a blanket and lay it in the floor so stuff wont gouge you and lay in the floorboard. Makes it allot easier on the back and neck!~!

 

[boomdriver]

Every booster will go bad a little different than the next!

Take the drivers seat out,fold up a blanket and lay it in the floor so stuff wont gouge you and lay in the floorboard. Makes it allot easier on the back and neck!~!

agree 100%

its not a lot, but it gives you enough room to get inside and get situated so that you're not half in half out and twisting your neck around like it was rubber...

That method (seat removed) helps me and I'm over 6' with several flat disc....takes me 3 weeks to get the courage up to do something like that...when I know its gonna hurt.

You have to d/c the rod that connects the pedal...then re-attach the new one.

NOTE:
check the new one against the old. Some rod lengths are different and this can be a problem. Make sure they are the same.

If you are gentle, you can pull the master cyl away without d/c any lines. Just tie it off to the alt with a string or wire. If you loosen the brake lines on the master, you have to go thru the entire bleeding process since those are at the pressure source. Avoid that at all cost.

Good Luck!

 

[chevyaddict]

Oh you bet... I hate having to bleed brakes on these vettes. Very difficult to get all the air out! Thanks for the tips!

 

[John Robinson]

While your resting under the dash look at the brake vacuum switch like Junk said they go bad. On mine it would not stay in adjustment because the plastic tabs had lost there tension and would not stay in place. On mine I was able to fix the vacuum leak by cutting off the end of the hose and pulling a little of the slack out and reconnecting it. If you have not got enough slack to do this go under the hood and cut the vacuum line and use a couple of plastic connectors and a piece of hose to lengthen it and pull it through the firewall enough to get it to connect. The seat removal is the only way to go and if you have a small step stool put it outside of the door so you can scoot your bottom onto it and swing you legs out and then stand up. I found that a lot easier way to get in and out with my bad back.

 

[chevyaddict]

Ok - I'm tackling this right now. First, I don't see this vacuum switch. I don't see any vacuum line under the dash at all or any vacuum line going from my engine compartment through the firewall inside. Does a 90 have this switch?

Aside from that, when I depress the brake pedal as I'm laying in the floor board it is DEFINITELY coming out of where the pedal rod is going into the booster so that means without a doubt that the booster is bad, correct? The diaphragm inside has gone bad?

 

[John Robinson]

Hope this helps

 

[boomdriver]

Ok - I'm tackling this right now. First, I don't see this vacuum switch. I don't see any vacuum line under the dash at all or any vacuum line going from my engine compartment through the firewall inside. Does a 90 have this switch?

Aside from that, when I depress the brake pedal as I'm laying in the floor board it is DEFINITELY coming out of where the pedal rod is going into the booster so that means without a doubt that the booster is bad, correct? The diaphragm inside has gone bad?

Abbo-lutely.

 

[chevyaddict]

The only problem I had is the rod was shorter so my switches weren't touching the pedal. Gotta still deal with that but my back was killing me. I decided to not take the seat out. Works great now though! I've been driving without boost for so long I forgot what it felt like to have complete power brakes!