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Old 6th October 2023, 07:20   #61
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by PYSO View Post
.. They did experience some brake sluggishness though…
So they also did encounter some changes in the brake behaviour. There could be other factors in play like Kms done (mine is 8000+), nature of braking, experienced etc. Can you request these to document the changes in the brake behaviour here?
I don’t know if you have driven in a convoy but as I was leading multiple times, my Jimny was subjected to a greater aggressive driving and braking. All the incoming traffic and events were relayed upon to the convoy as well for which they can be braking in anticipation.
However, everyone in my group did encounter brake degradation and many even encountered brake hardness. These were mostly who were either leading or sweeping the convoy.

I request you to please put down names here for future reference. Let the information out please.

Last edited by Turbanator : 6th October 2023 at 21:39. Reason: Jim= Jimny.
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Old 6th October 2023, 10:58   #62
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

I had done Kardungala, Pangong, Hanle, Umling La comfortably in Jimny Alpha AT 2 months back. Never faced any brakes related issues. In general, I felt the brake is weak in Jimny AT but thats about it.
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Old 6th October 2023, 11:02   #63
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

What is common in the experiences of many Jimny owners is that there seems to be definitely a braking issue in the Jimny specially at higher altitudes. (Every owner may attribute it to different things due to ignorance or experience). Serious accidents could happen due this problem and needs to be addressed urgently. I think the Jimny owners need to thank puohitanuj for documenting it and bringing it to the notice of Jimny owners who might be planning high altitude trips. I definitely think it is not an isolated case and merits attention.

Last edited by murlidar : 6th October 2023 at 11:06.
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Old 6th October 2023, 13:09   #64
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by Kashi053 View Post
In general, I felt the brake is weak in Jimny AT but thats about it.
Brake of Jimny is pathetic in day to day life and also in lower Himalayan hills. Every time it just missed the front or rear bumper of other cars. Anyway, the brake issue reported at higher altitudes are different and MSIL must find a solution.
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Old 6th October 2023, 16:03   #65
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by PYSO View Post
Tough to rely on the claims made by one person, when others in the same convoy have a different version of events. Please understand that the 4X4 community in India is rather well connected - there are lots and lots of other people you can reach out to, who have been to high altitudes with their Jimny.
This is even more scary! Say out of 100 cars, 10 cars are facing this problem! So this will be even harder for Maruti to pinpoint the problem and rectify it. Even if one accident occurs due to this braking issue, who is going to take responsibility?

Another thing I want to say is, if anyone faces this problem in Ladakh, please report it to Leh service centre as that is the place the problem can be replicated. Once the car is back to the plains it will be hard to detect the actual cause.
This issue is serious and needs urgent attention.

Last edited by Samba : 6th October 2023 at 16:09.
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Old 6th October 2023, 16:55   #66
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by Samba View Post
This is even more scary! Say out of 100 cars, 10 cars are facing this problem! So this will be even harder for Maruti to pinpoint the problem and rectify it. Even if one accident occurs due to this braking issue, who is going to take responsibility?
I am in talks with Maruti people and as per them, they will have a look at my Jimny and then try to contact people around Leh to get another round of feedback. I think a set of 3-5 cars would be enough to replicate the issues.

As of now, there are three groups of Jimny's:


1. Brake gets hard with extremely reduced braking
2. Brake pedal sinks in as if there is a leak but on inspection, there is none.
3. Brake feels half as effective but there is no sponginess or hardening.

These all sets of issues are not related to brake fading or wet brakes. Something is going on.

In all of these 3 sets, the brakes get auto-corrected at lower altitudes. I hope these three issues are interconnected and minor to resolve.

After talking to many Jimny owners, I am confident that 99% of users visiting higher altitudes will certainly come under at least 1 set from above.

Last edited by Turbanator : 6th October 2023 at 21:39. Reason: Please use full name of car- Jim= Jimny
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Old 6th October 2023, 17:57   #67
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

^ Does this vehicle have EGR?

During cold start ideally EGR should be shut but what if they have some system to let EGR on for fast warm up, just a random thought perhaps worth exploring.
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Old 6th October 2023, 18:33   #68
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by purohitanuj View Post
As of now, there are 3 groups of Jims:
1. Brake gets hard with extremely reduced braking
2. Brake pedal sinks in as if there is a leak but on inspection, there is none.
3. Brake feels half as effective but there is no sponginess or hardening.
In continuation to my earlier post on this thread, these three conditions you have mentioned make my assumptions of moisture/water in the brake fluid more robust.

Let’s forget about sensors/ABS/TC etc for the time being. The braking is a simple mechanism, where you apply a mechanical force on the pedal, and pressurises the hydraulic fluid, which in turn squeezes the brake pads on the rotor to stop the vehicle. Now here are my inputs as per your observations:

1) Brake gets hard with extremely reduced braking - assuming this is happening just at the start of the day after a cold/freezing night, the moisture in the brake fluid will be frozen and will reduce the viscosity of the break fluid. With this reduced viscosity, it would be difficult to reach the desired pressure to get the bite out of the brakes; hence you need to apply more force on the pedal. Similar to braking done on non-hydraulic operated cars. Also, as mentioned by you, ABS malfunctioned during this time, which somewhat points towards this theory.

2) Brake pedal sinks in as if there is a leak but on inspection, there is none - assuming this is happening after some considerable braking and driving is done. While braking, the friction of brake pads and rotor would considerably increase the temperature of the brake fluid, which in turn will vaporize the moisture and would create air bubbles in the fluid and these air bubbles will be compressible, and hence you feel the sponginess. That’s why bleeding of brakes is mandatory for air bubbles.

3) Brake feels half as effective but there is no sponginess or hardening - This is very subjective and can be related to the vehicle's design.

If I would be at MSIL Ladakh, I would troubleshoot it in freezing conditions and add certain amount of water to the brake fluid, replicate the scenario in some safe controlled conditions and see the results, if matching to yours.

Meanwhile can you please check what kind of DOT 3/4/5 fluid is going in the brake fluid tank? I just hope it’s not DOT 3.

Last edited by Axe77 : 6th October 2023 at 21:44. Reason: break- brake and similar. Please proofread before posting. [++ Few additional edits].
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Old 6th October 2023, 18:39   #69
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by Kosfactor View Post
^ Does this vehicle have EGR?

During cold start ideally EGR should be shut but what if they have some system to let EGR on for fast warm up, just a random thought perhaps worth exploring.
Unlikely, EGR is mostly found in turbo diesel engines.
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Old 6th October 2023, 19:01   #70
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by Turbolove View Post
Unlikely, EGR is mostly found in turbo diesel engines.
Are you sure? I think EGR is present in all modern petrol and diesel vehicles.
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Old 6th October 2023, 19:57   #71
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by NomadSK View Post
In continuation to my earlier post on this thread, these 3 conditions you have mentioned, makes my assumptions of moisture/water in the break fluid more robust.

.
Well it could be moisture but then how can these issues vanish in split second as soon as one revs the engine. I guess the moisture cannot go away that fast.

Also, I got these issue with 10-12 deg c temps outside while the car was running for hours. As I was wearing jackets, Air Con was also on. The front tyres should temps in excess of 40 dec c. Hence I think moisture is not at play here.

As per user manual, the brake fluid has to be DOT3.

Last edited by purohitanuj : 6th October 2023 at 20:09.
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Old 6th October 2023, 21:01   #72
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by purohitanuj View Post
Well it could be moisture but then how can these issues vanish in split second as soon as one revs the engine. I guess the moisture cannot go away that fast.
Not in a split second, for sure, but when the temperature of the fluid rises over some braking action. Mind you, the temperature of the brake pads and rotor would get pretty high pretty quickly for the moisture to vaporise in the fluid system.

Quote:
As per user manual, the brake fluid has to be DOT3.
As far as I remember, DOT3 has a lower viscosity and generally used in NON-ABS vehicles. For ABS vehicles, it’s DOT4 fluid. MSIL would be able to better answer this.

Last edited by Turbanator : 6th October 2023 at 21:18. Reason: minor edit.
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Old 6th October 2023, 21:11   #73
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

Brake Maintenance page from Jimny’s User Manual
Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes-img_1653.jpeg
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Old 6th October 2023, 21:37   #74
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by NomadSK View Post
assuming this is happening just at the start of the day after a cold/freezing night, the moisture in the brake fluid will be frozen and will reduce the viscosity of the break fluid.
In brand-new cars, I doubt moisture can mix so much with brake fluid when everything is so new and tight. Over the period it does get mixed as Brake oil is hygroscopic but to assume it's mixed at height then it vanishes due to braking at lower levels, does not sound convincing.


Quote:
While braking, the friction of brake pads and rotor would considerably increase the temperature of the brake fluid, which in turn will vaporize the moisture and would create air bubbles in the fluid and these air bubbles will be compressible, and hence you feel the sponginess.

Yes, these are signs of water mix in the brake fluid but, once absorbed by the fluid, you will need to change the complete fluid. It will not auto-correct when in plains.


Quote:
If I would be at MSIL Ladakh, I would troubleshoot it in freezing conditions and add certain amount of water to the brake fluid, replicate the scenario in some safe controlled conditions and see the results,
They don't need to add anything and instead should focus on why brakes are behaving differently.

We might see a change to a bigger brake booster in my opinion.
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Old 6th October 2023, 23:56   #75
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Re: Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes

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Originally Posted by Turbanator View Post
In brand-new cars, I doubt moisture can mix so much with brake fluid when everything is so new and tight.
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. Hence I don’t think it has anything to do with the car being new. Heated fluids while cooling down tends to absorb more moisture than in normal scenarios. This Heat will lead to moisture condensing in the hydraulic system of the brakes. 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.

Quote:
Yes, these are signs of water mix in the brake fluid but, once absorbed by the fluid, you will need to change the complete fluid. It will not auto-correct when in plains.
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.

Quote:
They don't need to add anything and instead should focus on why brakes are behaving differently.

We might see a change to a bigger brake booster in my opinion.
In my opinion, If and if this is the root cause of the problem, even the bigger brake booster won’t solve the problem.

This was my car at Jispa one fine morning, you can see the level of moisture/dew on the windshield. Probably the location has low dew point due to its lower altitude level.
Attached Thumbnails
Maruti Jimny AT | Brakes not functioning at low rpm at high altitudes-img_2056.jpeg  


Last edited by NomadSK : 7th October 2023 at 00:04.
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