[RijuC]

Originally Posted by Turbanator

We might see a change to a bigger brake booster in my opinion.

Can you please share some link or references from where we can source this bigger / better braking system and get it installed?

It is really surprising that despite of reporting this incident (thread started on 25th September); there is no reaction or response or investigation from MSIL end. They simply ignore this safety related issue of the Jimny. And Jimny sales is still on. Why automobile industry is so different than any other legacy or new generation industry where any such safety related issues reported by Customers are taken up in priority, defective product sales stops immediately etc?

It is either a design negligence by incompetent MSIL engineers, Inadequate R&D of MSIL, or a poor quality passed on to final product (other legacy Japanese companies term it as "fraud"), severe cost cutting and compromising the quality willfully, failure of adequate testing of the vehicle and ignorance by the MSIL top management knowingly (again a "fraud").

Now we understand why MSIL created such a hype around Jimny, just to willfully pass on an unfinished, untested and quality compromised product to Indian customers. MSIL is such a pathetic automobile manufacturer having absolutely no ethics.

[Turbanator]

Originally Posted by NomadSK

I think, Hydraulic brake fluid in the reservoir is not in the closed pressure system. The cap has a minor opening at the top to maintain the atm pressure inside.

No, Please go through this

The reservoir cap is vented and has a diaphragm that expands and contracts to maintain normal pressure inside.

https://www.repairsmith.com/blog/brake-fluid-reservoir/

Heated fluids while cooling down tends to absorb more moisture than in normal scenarios.

Why is brake fluid getting hot at hills on parked vehicles?

Any condensation that enters will exist as a pocket of pure water in the system rather than being absorbed into the fluid which could freeze in cold weather conditions.

Moisture/ water will get absorbed with Brake fluid, and you cannot separate it any longer, certainly not on its own when you are in plains. Also, Brake fluid has a very high boiling point so whatever moisture gets mixed, over a period is factored in. It's a known phenomenon and that's the reason Brake fluid is changed in cars on time-based intervals. Look at this-

Water boils at 100°C where as brake fluid with high boiling point will boil around 300°C, and low boiling point brake fluid will boil around 140°C.

Why is a low boiling point temperature not acceptable?

When driving aggressively on windy mountain roads or race circuits, brake pad can reach over 300°C. This high heat gets passed onto the brake fluid through the calipers, which can raise the fluid temperature over 200°C. If the brake fluid is repeatedly heated past its boiling point, some of the fluid vaporizes and creates bubbles within the brake lines. This is a very dangerous situation since this can lead what is commonly known as vapour lock, or simply the brakes not working. This occurs since the vapour is compressed instead of the fluid so the brake pads do not move.

https://www.frentech-uk.co.uk/wp-con...AKE-FLUIDS.pdf

Well technically, it can autocorrect after long drives and after continuously hitting of the brakes, raising the temperature of the hydraulic fluid above the boiling temperature of the water to completely vaporize and flush it out from the system.

Water or moisture in the brake system is not concentrated in any particular place; it gets mixed completely with brake fluid, and this is irreversible. You will have to flush old brake fluid and change it with new. Whatever effects of this moisture/ water in the brake system like sponginess/ less braking feel as mentioned by you are permanent and won't go away.

In my opinion, If and if this is the root cause of the problem,

No, moisture/ water getting in brake fluid at hills, resulting in loss of brake pressure and then automatically going away in plains, is impossible. You need to read a bit more on the subject.

even the bigger brake booster won’t solve the problem.

Originally Posted by RijuC

Can you please share some link or references from where we can source this bigger / better braking system and get it installed?

It's my thoughts . Whether it's the actual reason or not, we will find out in some time. I don't think, as of now, we have any different (bigger) brake booster. But we don't have altitudes like Himalayas elsewhere where Jimny is being sold.

We need to be patient; no manufacturer can do a fix so soon, especially if the problem is related to a mechanical part. What they should instead do is issue a warning to Jimny owners to be careful with brakes at high-altitude.

[shankar.balan]

Originally Posted by Turbanator

No, Please go through this

When driving aggressively on windy mountain roads or race circuits, brake pad can reach over 300°C. This high heat gets passed onto the brake fluid through the calipers, which can raise the fluid temperature over 200°C. If the brake fluid is repeatedly heated past its boiling point, some of the fluid vaporizes and creates bubbles within the brake lines. This is a very dangerous situation since this can lead what is commonly known as vapour lock, or simply the brakes not working. This occurs since the vapour is compressed instead of the fluid so the brake pads do not move.

Most cars have power brakes and power steering and boosters and power everything nowadays.
Brake power boosters have been around for a long long time. One of the reasons that we always learned in the early years (whether in the hills or the plains is immaterial) is to never switch off the engine and coast in neutral while riding (however lightly) on the brakes, when going along a decline (down slope). Over the period of a few minutes the pressure built up in the brakes will dissipate and the brakes simply won’t work. They simply won’t be able to hold. If you have a mechanical parking brake then maybe you can pull that in such a situation. But most cars don’t have a mechanical parking brake any more. It is therefore, important to check the health of the brake fluid once a year, top up and bleed the brakes if necessary and inspect the brake booster as well from time to time.

Just my two bits based on experience.

[Turbanator]

Originally Posted by shankar.balan

Most cars have power brakes and power steering and boosters and power everything nowadays.

Yes, but you still need brake oil reservoirs

The current issue discussed here is different, not due to driving with the engine off.

[purohitanuj]

Originally Posted by Turbanator

No, Please go through this

The reservoir cap is vented and has a diaphragm that expands and contracts to maintain normal pressure inside.

https://www.repairsmith.com/blog/brake-fluid-reservoir/

Thanks for this. I have noticed that in my Jimny, the brake fluid container cap is loose. Like it doesn’t tighten all the way. Nothing is broken or anything like that but its that way from factory. In fact I have noticed few more Jimnys whose caps were not snugly tightened/fitted. Can this be the issue in anyway?
I had previously asked service center about it and they said one can drive even without the cap but its there to prevent dirt from getting in.

[shankar.balan]

Originally Posted by purohitanuj

Thanks for this. I have noticed that in my Jimny, the brake fluid container cap is loose. Like it doesn’t tighten all the way. Nothing is broken or anything like that but its that way from factory. In fact I have noticed few more Jimnys whose caps were not snugly tightened/fitted. Can this be the issue in anyway?
I had previously asked service center about it and they said one can drive even without the cap but its there to prevent dirt from getting in.

Most cars brake fluid reservoir caps have that slight ‘play’. They dont really tighten as sharply as normal plastic bottles do for example.

[Turbanator]

Originally Posted by purohitanuj

I have noticed that in my Jimny, the brake fluid container cap is loose.

So, the reservoir or container is only to store the Brake fluid. Pressure is built into the master cylinder and supplemented by brake boosters.

https://www.youtube.com/watch?v=I4Ka4__ws1E

asked service center about it and they said one can drive even without the cap but its there to prevent dirt from getting in.

Not just the Dirt but most importantly, moisture. It's wrong to drive without a cover. Temporarily, there will be no effect but in very short span of time, brake fluid will absorb moisture as well as dirt.

[NomadSK]

Originally Posted by Turbanator

The reservoir cap is vented and has a diaphragm that expands and contracts to maintain normal pressure inside.

Unfortunately that’s not true. Not every car has a diaphragm. The fluid in the reservoir works under gravity. It only gets momentarily pressurized in the master cylinder, while hitting the brake paddle.

Why is brake fluid getting hot at hills on parked vehicles?

While driving over night the fluid will get heated and during cooling down will have more tendency to absorb moisture.

Moisture/ water will get absorbed with Brake fluid, and you cannot separate it any longer.

Water or moisture in the brake system is not concentrated in any particular place; it gets mixed completely with brake fluid, and this is irreversible.

Sorry, but Again it’s not correct, different fluids with varying boiling points can be separated, a simple distillation. It’s all a game of temperature and pressure.

No, moisture/ water getting in brake fluid at hills, resulting in loss of brake pressure and then automatically going away in plains, is impossible. You need to read a bit more on the subject.

While driving and till reaching the plains, If moisture with low BP is vented out completely from the system with hot fluid having higher BP, the brakes would tend to behave normally. But till the time moisture would be there, one would tend to feel the sponginess in the brakes. Infact the sponginess is felt only when moisture in the fluid vaporizes, that itself means the temperature of the system is above 100C. I’m Just throwing my cards.

Also, I’m not saying this is the sole reason, but this could be the reason. As at height and plains, what are we dealing differently, it’s temperature, pressures and moisture in the air, only fluids behave differently in those conditions and not the mechanical parts. Correct me if I’m wrong. Definitely MSIL has to work on this to come out with a solution before anything untoward happens. Yeah even after 20+ years of dealing with fluids I have to read more on certain things. Thanks for listening.

A method of removing water from a mixture of glycol and water comprises introducing a feed mixture of glycol and water to a distillation column, and collecting a first concentrated glycol-water liquid as still bottoms. The first concentrated liquid is then conveyed to a reboiler where a portion of that liquid is vaporized to form a reboiler vapor and a second concentrated glycol-water liquid. The reboiler vapor is returned to the still for intimate contact with the feed mixture of glycol and water in the distillation column. The second concentrated liquid is then conveyed to a water exhauster at a temperature and pressure such that an equilibrium vapor of said second concentrated liquid, at said conditions, has a glycol/water weight ratio of at least 0.54. At this condition, a portion of the second concentrated glycol-water liquid is vaporized in the water exhauster to form a third concentrated glycol-water liquid and an equilibrium vapor in contact with the third concentrated liquid. A portion of the equilibrium vapor is then condensed and the condensate is removed from the exhauster to allow for further vaporization of said third concentrated liquid, thereby increasing the glycol percentage of said third concentrated liquid. In a second embodiment of the present invention the feed mixture to the distillation column is preheated such that the feed liquid has an equilibrium vapor glycol/water weight ratio of 0.54.

[Turbanator]

Originally Posted by NomadSK

Not every car has a diaphragm.

As mentioned by another member, you can even keep the cover open. That changes nothing relating to operation and that has nothing to do with the problem being discussed here.

different fluids with varying boiling points can be separated, a simple distillation. It’s all a game of temperature and pressure.

No one is saying you cannot but definitely not on its own in a brake system in a car.

Yeah even after 20+ years of dealing with fluids I have to read more on certain things.

Let's not come up with a hypothetical situation based on fluid dynamics. I have zero knowledge about the fluids but I absolutely do not agree that a commercial-grade system that uses brake oil produced for a specific job will first gain moisture/ water at heights and then will lose on its own and that too only on a specific vehicle - Jimny.

[Kosfactor]

Originally Posted by NomadSK

While driving over night the fluid will get heated and during cooling down will have more tendency to absorb moisture.

I have driven without the brake reservoir cap itself, yes there is the risk of dirt going inside but I didn't do it on purpose.

Brakes were perfectly normal.

Brake fluid absorbing moisture and it hampering braking takes some time, won't happen overnight. If this is a widespread problem all vehicles in that area will get affected, Jimny or not, after all the reservoir cap would be a standard Maruti part probably used in many other cars.

[NomadSK]

Originally Posted by Turbanator

Let's not come up with a hypothetical situation based on fluid dynamics.

Sir, This is not at all a hypothetical situation. There have been many many incidences where moisture mixing with fluids have created havocs in the hydraulic system or fluid lines. There’s one aviation disaster related to this. Problem is To replicate such conditions/scenarios it needs time money and wish to do so.

I absolutely do not agree that a commercial-grade system that uses brake oil produced for a specific job will first gain moisture/ water at heights and then will lose on its own and that too only on a specific vehicle - Jimny.

That’s perfectly fine, we can always agree to disagree. I will surely keep an eye on this thread for the outcome from MSIL.

Originally Posted by Kosfactor

I have driven without the brake reservoir cap itself, yes there is the risk of dirt going inside but I didn't do it on purpose.

That was my point, the break system is not a pressurized close loop system. The cap is there just to not spill off the fluid during momentarily pressurization.

Brake fluid absorbing moisture and it hampering braking takes some time, won't happen overnight.

There’s no time line to it, in my few posts before, check on the dew content of the windshield on my car at the same location where the OP has got the problem. If it can be on the windshield, it can be in the reservoir too. Also, If fluid is hygrospic and environmental condition are deemed fit, it will simply absorb moisture.

[sammysossa]

Although I am yet to experience the issue myself, the mere thought of brake failure is enough for me cancel my travel plans and dissuade anyone from buying a Jimny, for now. Unfortunately for a few like me, traveling in higher altitudes is a necessity since this is home.
I have to visit Sissu and Jispa and have postponed the trip just because of this issue. For a car that is being sold using videos of high altitude journeys, it doesn't look so great now, does it? Maruti Suzuki's silence is not confidence inspiring. They should give due acknowledgement to the concerns and inform/advice the owners so we may make informed decisions. To put it simply, I am heartbroken.
And lets refrain from shooting the messenger. Had it been not for this thread we would have probably heard about this issue after looking at a mangled remains of a Jimny.

[Hoopoe]

Folks this is an excellent and intriguing discussion. I did some research on this and it appears that the start-stop technology is more sophisticated than it appears.

It seems that temperature and battery both play a crucial role in this. We know that in the issues mentioned temperature is a factor and we also know that batteries tend to have lower efficiency in cold temperatures.

Please see this video to understand the start-stop system better and draw your inferences:

https://www.youtube.com/watch?v=TTBN8Ic57Gg

[bobbyblr]

Hi Folks,

There are 2 options that came to my mind regarding Jimny braking.

Option-1: Upgrading the Brake Booster
When I test drove the Jimny 5-door AT, I could get the same braking experience of my Alto 2009. I have also test drove my uncle's Corolla Altis 4 years back. The brakes in the Corolla Altis are like feather touch meaning with just a light touch of the feet the car came to a sudden halt.
So searching the Youtube, I came across this video from Brake Caliper Booster BCB channel showing the difference and improvement in stopping time & distance from 100kmph to 0kmph with the new brake booster. Below is the link to the video. The audio is not clear and the language is Chinese or Japanese.

https://youtu.be/XjctFr_p9vk?si=JvV0l-0QgMgrJnu8

Option-2: Testing inside Environment Controlled Dyno / Climatic Dyno chambers
If there is any Dyno testing in India simulating the Temperature, Humidity and Atmospheric Pressure (based on the altitude) at which the Jimny brakes were failing will help in evaluating the issue better.
Also an OBD tool can be connected to monitor the Brake Vacuum from it's sensor.
I know that this testing is expensive and I assume Suzuki or Maruti Suzuki might have performed this test. Any test report from them will be very helpful to us.

These are just my thoughts.

[RijuC]

Environment controlled chambers are available in India for parameters like temperature and humidity. Professionally, I participated in such testing for control panels (loaded with electronics, power supplies, sensors and modules/ cards). I am not sure about 3 variable parameters together involving barometric pressure. It is extremely difficult to keep barometric pressure as variable in these chambers.