Brake booster failing?

[Not_An_Abba_Fan]

I have an old Triumph TR6 - their brakes are notoriously hard to bleed- it's very difficult to get a full pedal. Some of the blokes jam the brake pedal down hard overnight with a stick then rebleed the next day. The theory is that the pressure and time cause any microbubbles in the fluid to coalesce into bigger bubbles that will bleed out.
I've never needed to do it with a Holden but if your running out of options it might be worth a try.

Try doing a 40 series Landcruiser with slave cylinders top and bottom, have to unbolt the backing plate and rotate it to get all the air out. Unless you had a pressure bleeder, those things are worth their weight in gold.

 

[Immortality]

Not that it's relevant to this problem but I was watching one of the engineers at work replace the brake pads on the boss's boat trailer a few weeks ago. The pads coming out weren't worn badly but still they were been replaced. The engineer than went to bleed the system when I noticed the bleed nipples on the callipers were fitted incorrectly and were in the bottom fitting on both sides!

I did mention it to him but the problem wasn't remedied. It's a big boat so here's hoping his new Dodge ram 1500 can stop it. Or not?

 

[Turd Ferguson]

Not that it's relevant to this problem but I was watching one of the engineers at work replace the brake pads on the boss's boat trailer a few weeks ago. The pads coming out weren't worn badly but still they were been replaced. The engineer than went to bleed the system when I noticed the bleed nipples on the callipers were fitted incorrectly and were in the bottom fitting on both sides!

I did mention it to him but the problem wasn't remedied. It's a big boat so here's hoping his new Dodge ram 1500 can stop it. Or not?

As someone who used to repair trailers and caravans a boat trailer even having semi operable brakes is impressive in itself.

Had a customer tow a 3.5 tonne boat from Brisbane to Sydney with no working trailer brakes with his Audi Q7

Had this 4 tonne boat trailer come in for repairs:

 

[woteva]

I'm very lucky the hub/drum came off here as I don't think I could have got that axle nut undone.
The top brake pad still looked OK. The other one was left on the road somewhere.

 

[Fachoo]

Firstly, disc/drum rear came with both 15/16 and 1" bore masters....No difference with them....Go look at VN to VR....Factory disc rears, and 15/16 masters...1" bore was used on 6 banger cop cars around this era too.....Rellie has a VP ex-cop car with single diaphram booster and 1" bore master....Even early commodores with disc rears had 15/16 masters...The 1" bore masters are the harder ones to find...And yes they were fitted to disc reared cars, rather than drum rears....

Booster..The V8's had the double diaphram one...Not sure if the 6 ever came out from the factory with it....And my swapping had zippo to do with engine changes....

If you hear air escaping when you depress the brake pedal, with the engine running, the booster is stuffed....So giving advise that it is normal, is scary advise....

we:re talking atmospheric air from pedal movement not loss of booster pressured air as you keep implying, obviously you don:t know the difference.

Read what abba posted

There is a difference between a continuous hiss and the momentary hiss as you hit the brake pedal. I'm referring to the momentary hiss when you push the pedal down, some cars do it, some don't. I've had both a VS and VT do it, booster was fine.

 

[Immortality]

Calm down mate.

If you can hear air when pushing the brake pedal you can't be certain it is not the seal failing on the input shaft. Common enough and something I have personally experienced. Certainly not something to simply discount at any rate like you suggest.

 

[vc commodore]

we:re talking atmospheric air from pedal movement not loss of booster pressured air as you keep implying, obviously you don:t know the difference.

Read what abba posted

A mind reader....You must be a multi millionaire.

Having experienced air loss from depressing the brake pedal, with the engine running (which the op has mentioned right at the beginning, should you wish to read things properly and comprehend them), I do know the difference and can say with 100% confidence, brake boosters failing make these sounds.

So a bit of friendly advise...Learn to actually read all the symptoms described rather than partial symptoms...

 

[MikeC]

I've never done this test- but would a vacuum gauge pick up this leak - vacuum drops when the brake pedal is pressed?

 

[Skylarking]

... If you can hear air when pushing the brake pedal you can't be certain it is not the seal failing on the input shaft. Common enough and something I have personally experienced. Certainly not something to simply discount at any rate like you suggest.

As you apply the brake, the diaphragm moves because atmospheric pressure forces air into the rear of the diaphragm through the filter. That’s by design and may or may not cause air squeal as the air rushes in.... If you then hold pressure on the brake pedal, pressure equilibrium is reached and any and all air squeals will stop. If it doesn’t stop, that’s when it’s safe to say you have a problem.

If you hold your foot on the brake and continue to hear air squeal, this indicates pressure equilibrium can’t be reached and air is leaking from the rear of diaphragm to vacuum side of the diaphragm which is not a good thing...

Another booster test is with the engine off. Since the booster is a vacuum reserve and should hold vacuum for quite some time, it will allow a few full brake applications before the vacumm reserve is depleted and assistance is lost with the result being the pedal going hard.

(Also parking the car for a week or more will still see vacuum held within the booster so it’s a good test of a slow leak... I still have vacuum reserve after months of not driving... )

The important thing when people experiance brake issues is that if they don’t fully understand the principles of hydraulic brakes and vacuum assistance that they go to a brake specialist. Best for us all is if they stop faffing about with things they don’t fully understand and risk other peoples lives with whom they share the roads with

PS: the booster in part behaves like old blacks ist bellows and as air moves on and out the bellows makes noise... Nothing wrong there...

 

[vc commodore]

As you apply the brake, the diaphragm moves because atmospheric pressure forces air into the rear of the diaphragm through the filter. That’s by design and may or may not cause air squeal as the air rushes in.... If you then hold pressure on the brake pedal, pressure equilibrium is reached and any and all air squeals will stop. If it doesn’t stop, that’s when it’s safe to say you have a problem.

If you hold your foot on the brake and continue to hear air squeal, this indicates pressure equilibrium can’t be reached and air is leaking from the rear of diaphragm to vacuum side of the diaphragm which is not a good thing...

Another booster test is with the engine off. Since the booster is a vacuum reserve and should hold vacuum for quite some time, it will allow a few full brake applications before the vacumm reserve is depleted and assistance is lost with the result being the pedal going hard.

(Also parking the car for a week or more will still see vacuum held within the booster so it’s a good test of a slow leak... I still have vacuum reserve after months of not driving... )

The important thing when people experiance brake issues is that if they don’t fully understand the principles of hydraulic brakes and vacuum assistance that they go to a brake specialist. Best for us all is if they stop faffing about with things they don’t fully understand and risk other peoples lives with whom they share the roads with

PS: the booster in part behaves like old blacks ist bellows and as air moves on and out the bellows makes noise... Nothing wrong there...

So by depressing the brake pedal, whilst the car is running and a rough idle appears along with air noise, what would this indicate?