[srini1785]

Originally Posted by Jeroen

What does the switch do? I suspect it just closes when no power/engine shut down?

Simple it tells you if there is sufficient vacuum. If, say , the pre set value of the switch is around -0.05bar then when the vacuum reaches this value then the switch opens (or closes, as the case maybe) telling that all is well and brake booster works.

[Jeroen]

Originally Posted by srini1785

Simple it tells you if there is sufficient vacuum. If, say , the pre set value of the switch is around -0.05bar then when the vacuum reaches this value then the switch opens (or closes, as the case maybe) telling that all is well and brake booster works.

Thanks, my bad, I thought it was more a valve. But are you sure about the above?
If I read the description of this switch on the internet it is actually switches on the vacuum pump.

See https://www.amazon.co.uk/Dracarys-Ac.../dp/B07H9664YM

So not an indication. If it an indication or alarm, how will that show on the dashboard.

Jeroen

[srini1785]

Originally Posted by Jeroen

Thanks, my bad, I thought it was more a valve. But are you sure about the above?
If I read the description of this switch on the internet it is actually switches on the vacuum pump.

See https://www.amazon.co.uk/Dracarys-Ac.../dp/B07H9664YM

So not an indication. If it an indication or alarm, how will that show on the dashboard.

Jeroen

My bad too, It looks like it acts both as a valve and a switch. It switches on the pump when vacuum falls below -0.04 bar and switches off the pump when the pump reaches -0.06bar. So there you have it.

Yes it does not provide any indication , however its pretty easy to tap a wire off the circuit to indicate if vacuum is ON or OFF.

[Sutripta]

Originally Posted by sridhar-v

Slightly off topic, but possibly relevant:-

Early to mid 1990's. I was driving my business partner's Tata Sierra to Mumbai, with some family members. It was one of the first 50 cars sold. (old school diesel engine with a glow plug and all that!).
When climbing down the infamous Bhor Ghat the brakes went all wooden. I immediately downshifted to first gear and then literally stood on the brake pedal. Due to the slope the diesel pump started sucking air and the engine sputtered and coughed like mad.

What did you do about the steering when it lost assist?

Sutripta

[dhanushs]

Originally Posted by Sutripta

What did you do about the steering when it lost assist?

Sutripta

As long as the crank is turning, the steering might not have lost assist, since it was the old Hydraulic pump.


------------------------------

Looks like lot has been going on after this!... Will have a recap and follow.

Originally Posted by dhanushs

Sounds like a vacuum issue to me. Surprised there is vacuum issue when the car is not even stalling. Agree it’s a safety issue, but I’m sure this is something the company can easily fix.

Also - reading all the complaints, I’m sure there is still braking, just no assist. So you have to press the pedal a lot harder. Like when you brake with the car engine not running.

Also - Off-Topic. Braking in the highest gear isn’t happening guys, in any car. One should always try and downshift and use engine braking along with the pedal, except may be its for just slightly slowing down.

[sridhar-v]

Originally Posted by Sutripta

What did you do about the steering when it lost assist?

Sutripta

It was hydraulic assist steering.So fortunately no issues cropped up there. In the back of my mind I was always thinking of a place to ram the car, to stop it, in case I could not slow it down.

[Sutripta]

Originally Posted by dhanushs

As long as the crank is turning, the steering might not have lost assist, since it was the old Hydraulic pump.


------------------------------

Originally Posted by sridhar-v

It was hydraulic assist steering.

The vacuum pump also used to be driven off the alternator. So by that logic, engine driven on the overrun by the vehicle, everything should be honky dory.

Had an Armada Grand which would stall on the overrun. And when you tried to change down, say before entering a corner, you would suddenly find that you were without brakes, and essentially no steering. (In that moment don't believe all the 'the brakes are still there. Just stand on them. The steering is still there, you just have to tug harder.')

[dhanushs]

Originally Posted by Sutripta

The vacuum pump also used to be driven off the alternator. So by that logic, engine driven on the overrun by the vehicle, everything should be honky dory.

Ahh.. OK, now I get your point. But, I think his case was due to lack of vacuum because of repeatedly jamming the pedals (downhill) and the pump unable to compensate it. May be a tank would've helped. Not because of the crank not driving the pumps (Steering and Vacuum)

[a4anurag]

The vacuum pump and check valve in line to the booster in my Creta 1.6L CRDi

Marked the vacuum line from the pump to the booster in Yellow.


Marked the check valve in red and labelled it

[Jeroen]

Originally Posted by a4anurag

T
Marked the check valve in red and labelled it

Thanks for showing this. Your check valve looks remarkably similar to the one I showed earlier on my nearly 40 years old Mercedes. As I mentioned before, some designs are just beyond improvement!

Jeroen

[Jeroen]

I just came across this nice animation video. It gives a good, simple, overview of how a typical brake booster works

https://www.youtube.com/watch?v=wbTUvp-tD5M

Note that the brake master cilinder just gets bolted on to the brake booster. The piston rod pushes to the piston of the brake master cilinder. I have come across a few posts where member car suffer from brake fluid leaks and apparently the fix was to replace the booster. That is unlikely. Though the brake booster and brake master cylinder work in tandem, they are (mostly) two very distinct different/seperate devices. Only bolted together.

This one is also pretty good

https://www.youtube.com/watch?v=LThrL8Jjsgc

Enjoy.

Jeroen

[Venkatesh.H]

I have come across a few nice explanations of brakes working.

There are many parts in the brake system, failure of any one of following parts will give wooden feeling OR failure of braking system.

- defective/leaky vacuum hose connection.
- defective check valve which is responsible for maintaining set vacuum in the booster.
- defective/leaky diaphragm in booster will equalise vacuum pressure to atmospheric pressure.
- ceased/leaky piston assembly.
- leaks in brake fluid hoses, which finally applies hydraulic pressure to activate brakes.

https://youtu.be/bMg_j5_AGMg

https://youtu.be/ZgzeM0KRY6A

Hope Kia and Hyundai come with thorough explanations and attend to these issues at the earliest.

Venkatesh

[robbie_KL]

Been following this thread since day one. Frankly speaking, as far as I am concerned, if i step on the brakes, the car should slow down, with the breaking force being proportional to the force applied by my foot on the brake pedal. With the exception of ABS on loose, sandy surface, this basic behavior of a car should stay constant across all manufacturers and models. Any advancement, be it electronic or mechanical, or even a cost effectiveness measure applied by a manufacturer, that alters this basic behavior is purely undesirable.

[vrprabhu]

Originally Posted by Venkatesh.H

....

- This is also one of the reason why AUTO boxes have good breaking capability.

- Yet to experience breaking and RPM details on seltos manual gear box.

Can we please type 'brake' instead of 'break'?

Please??

I am sure that none of us intend to 'break' our respective vehicles.

Will help preventing me from breaking my head!! May be I am highly sensitive?

Or, is it that I am not up-to-date with the permitted usage of the word?

[Jeroen]

Originally Posted by robbie_KL

Been following this thread since day one. Frankly speaking, as far as I am concerned, if i step on the brakes, the car should slow down, with the breaking force being proportional to the force applied by my foot on the brake pedal. With the exception of ABS on loose, sandy surface, this basic behavior of a car should stay constant across all manufacturers and models. Any advancement, be it electronic or mechanical, or even a cost effectiveness measure applied by a manufacturer, that alters this basic behavior is purely undesirable.

In principle I agree with you. But unfortunately that is not how it works. If your ABS kicks in you will definitely notice from the feel of the pedal. In some countries during driving lessons you will be exposed to this as part of the curriculum.

If the booster fails the pedal force required becomes much more. The biggest problem I see that the difference between normal and failed condition is way too much. The same is true for power steering. Try and steering a car without power steering is really difficult (e.g. when being towed).

But then again, brake boosters failure are rare, luckily. I think what the problem is here, is that we just don’t really know what happened.

Jeroen

Jeroen