[dr_TJ]

Help Needed

Dear Thar owners, as you might have seen my posts regarding my issue of brake pedal becoming stiff after overnight parking. I got my vacuum pump replaced as per inputs from Mahindra's technical team. Vacuum hoses were also checked and vacuum was measured with a vacuum gauge. All found to be normal.
It seems there is some issue with the check valve (might be some leak in the rubber gasket around the valve or the valve itself) located on the Brake booster or the connection in between the check valve and vacuum hose.
Yes, I just park my car and switch off the engine, No brake pedal pressing after the engine is switched off, but the pedal is hard to press next morning. Also, braking performance and pedal feel is absolutely normal.

I just decided to check out the parts like vacuum hose, Check valve etc in Boodmo.
Few points have led to a confusion now.

Picture from Team-bhp official Thar review, Thar Diesel AT here. Note, the White check valve and Hose, No Hose clamp here. Also no hose connecting to the brake fluid reservoir and master cylinder

Picture is of my engine bay, Thar Diesel AT, No hose clamp and hose connecting to the master cylinder



Now check these two pictures, don't know if it is Diesel MT or AT, but I can clearly see a Hose with hose clamp connecting the brake fluid reservoir

Is this extra hose present only on Diesel MTs and not on Diesel ATs? Can someone clarify it?

Another confusion



Check this brake booster check valve connection with the vacuum hose as per Boodmo. There is a hose clamp shown in the diagram but I don't see a hose clamp on the vacuum hose connecting to the check valve on my Thar as well as on the Thar in our official review post.


Need some help in this matter. Mahindra service center guys and technical team is absolutely clueless regarding my issue. I suspect a check valve or connecting hose issue.
Please help.

[Aditya]

Mahindra Thar brake pedal hardens after overnight parking; service station clueless - Post moved to a new thread.

[dr_TJ]

Can anyone help me with any contacts or inputs to help me establish some contact with Mahindra's higher technical team?

[comfortablynumb]

Originally Posted by dr_TJ

Can anyone help me with any contacts or inputs to help me establish some contact with Mahindra's higher technical team?

Don't know about technical team, but if you haven't already done it, I would suggest writing a stinker to this person, with a link to this thread. When my Scorpio had a few issues (long back), I had got quick responses by using this channel. Of course, it was a different individual, but the escalation process was same. Info taken from https://auto.mahindra.com/mahindra-vehicle-faqs

[jeeva]

Originally Posted by dr_TJ

Check this brake booster check valve connection with the vacuum hose as per Boodmo. There is a hose clamp shown in the diagram but I don't see a hose clamp on the vacuum hose connecting to the check valve on my Thar as well as on the Thar in our official review post.

I am not a Thar owner. But the second hose that you are talking about, I think should be connected to the vacuum reservoir, which in your case is absent? The hard brake pedal must be the result of a vacuum leak or insufficient vacuum after being parked overnight.

[dr_TJ]

Originally Posted by jeeva

I am not a Thar owner. But the second hose that you are talking about, I think should be connected to the vacuum reservoir, which in your case is absent? The hard brake pedal must be the result of a vacuum leak or insufficient vacuum after being parked overnight.

I have seen picture of the engine bay of Thar Diesel AT owned by BHPian ph03n!x, It doesn't have the second hose connected to the brake fluid reservoir.

There seems to be some design difference between the Automatic and Manual. Only a Mahindra technician can clear the doubt.

[saket77]

This could be a result of small vacuum leak from the pipe/valve or the booster. The pipe/ joint should be the first suspect.

[dr_TJ]

Originally Posted by saket77

This could be a result of small vacuum leak from the pipe/valve or the booster. The pipe/ joint should be the first suspect.

The vacuum hoses and their joints were inspected twice at service center, reported as normal. I don't know if they checked the check valve or not.
But I suspect it might be the check valve on the brake booster causing this issue.
Must be a very minor and slow leak.
I am already tired of multiple visits of my new car to the service center

[thanixravindran]

Originally Posted by dr_TJ

I have seen picture of the engine bay of Thar Diesel AT owned by BHPian ph03n!x, It doesn't have the second hose connected to the brake fluid reservoir.

There seems to be some design difference between the Automatic and Manual. Only a Mahindra technician can clear the doubt.

I don't own a Thar but generally isn't Clutch and Brakes share the Brake oil in Manual transmission cars? So is it possible that the hose you are showing goes to the Clutch system in MT which is absent in AT system?

I may be completely wrong but experts can clarify here.

[dr_TJ]

Originally Posted by thanixravindran

I don't own a Thar but generally isn't Clutch and Brakes share the Brake oil in Manual transmission cars? So is it possible that the hose you are showing goes to the Clutch system in MT which is absent in AT system?

I may be completely wrong but experts can clarify here.

Yes, you are correct. After checking out Thar MT and AT engine bay photos, I have good understanding now.

MT Thar and other cars with Hydraulic clutch has that extra hose. AT cars don't have that.

As per my Brake pedal hardening issue after overnight parking, I have read about similar issue on other cars. Most suggest of a slow vacuum leak and to check the vacuum check valve.

[thanixravindran]

Originally Posted by dr_TJ

As per my Brake pedal hardening issue after overnight parking, I have read about similar issue on other cars. Most suggest of a slow vacuum leak and to check the vacuum check valve.

What happened to that missing clamp in your car that you show in the Boodmo parts picture? Did you checked with the service manual at Mahindra service center (not sure whether you will be allowed to do it) or have they replied about the hose clamp?

By check valve leakage, you mean do they not close fully and is there a way to test it like vacuum test by removing it?

[dr_TJ]

Originally Posted by thanixravindran

What happened to that missing clamp in your car that you show in the Boodmo parts picture? Did you checked with the service manual at Mahindra service center (not sure whether you will be allowed to do it) or have they replied about the hose clamp?

By check valve leakage, you mean do they not close fully and is there a way to test it like vacuum test by removing it?

As per the service center guys, there is no clamp on that hose on any Thar right from the factory.

I will have to remove the Check valve and check it for leakage. The brake vacuum leaks out slowly over a period of 10-12 hours, meaning the vacuum leak is very minor. That is the reason why it is hard to diagnose.

Prior to the first inspection of my car, brake pedal use to get hard after 4-5 hours of parking. I asked the service center to check the hoses, and the joints.
The issue was fixed for a few days, Brake pedal felt normal even after 12 hours of parking, but the issue recurred.
This time though, brake pedal hardening issue is after overnight parking of roughly 10-12 hours.

So, this time, I plan to check the hoses and check valve myself

[NvrGivUp]

Originally Posted by dr_TJ

As per my Brake pedal hardening issue after overnight parking, I have read about similar issue on other cars..

I have the exact same issue with my Nexon XZA+ P. I did not find it in the first couple of months. But, it started may be after couple of months. I have visited SC many couple of times and I was told that it is quite normal and I don't have to worry about that. They claim that this happens because of the hand brake that I'm using. I could not check without the hand brake as the vehicle tends to move back even though the parking area is flat.

[dr_TJ]

Originally Posted by NvrGivUp

I have the exact same issue with my Nexon XZA+ P. I did not find it in the first couple of months. But, it started may be after couple of months. I have visited SC many couple of times and I was told that it is quite normal and I don't have to worry about that. They claim that this happens because of the hand brake that I'm using. I could not check without the hand brake as the vehicle tends to move back even though the parking area is flat.

I had similar doubt that this issue might be because of handbrake, I also had to deal with rear drum brake knocking sound after 2 weeks of ownership. Got that fixed in the service center. They opened the left drum brake to inspect and clean it.

A quick Google search about brake pedal hardening after overnight parking shows similar issues being reported on Lexus, Nissan and Audi cars as well.

For petrol engines, Vacuum is created by the intake manifold. So might be something different on your Nexon.

But If possible, please get your vacuum check valve replaced. It might fix the issue.

[jaideepshinh]

Hi Dr_Tj,

When pressing the brake pedal, ask someone to be as close to it as possible. Do you hear a light hissing sound?

A normal failure point is the rubber seal gasket on the other side of the brake booster (where the brake pedal link connects). This usually fails before the other items you are looking at.

best of luck!

Jaideep