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Old 23rd March 2014, 19:00   #46
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Default Toyota Fortuner AT (2013) - Brake related question

Team: I need your views re; brake related question. This has been on my mind for sometime now.

About 45 days ago, I took the vehicle through mud for about 200 meters. Vehicle speed wasn't much. Max 20 kmph. Whenever I braked (to slow down) in the mud, I felt as if there was something that had come in between the brake pad/breaks. It happened few times. There was no impact on the braking though. But it didn't feel right. I couldn't get off in the mud to check. However, when I came off the mud and on to the road, the brake worked just normal. I did not get that 'feeling' which I got when I had braked in the mud. Since then I haven't experienced that feel again and the brakes seem to be doing ok. As on date, vehicle has done 17000.
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Old 24th March 2014, 07:11   #47
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Team: I need your views re; brake related question. This has been on my mind for sometime now.

About 45 days ago, I took the vehicle through mud for about 200 meters. Vehicle speed wasn't much. Max 20 kmph. Whenever I braked (to slow down) in the mud, I felt as if there was something that had come in between the brake pad/breaks. It happened few times. There was no impact on the braking though. But it didn't feel right. I couldn't get off in the mud to check. However, when I came off the mud and on to the road, the brake worked just normal. I did not get that 'feeling' which I got when I had braked in the mud. Since then I haven't experienced that feel again and the brakes seem to be doing ok. As on date, vehicle has done 17000.
How does the disc plate look like? Any scratches?

I feel the mud could have entered bergen the disc plate and pads causing braking feel to be low. I guess the pads were not getting enough grip to stop the car but when you were on normal road things cane back to normal.

Anurag.
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Old 24th March 2014, 08:28   #48
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Default Re: Strange loss of braking ability. What happened?

OK, last saturday night I experienced the same on my 10,7xx kms run Fiesta 1.6 S. The car decelerated initially, but after a brief moment, brakes just din't feel right! I then stomped on the brakes, ABS cut in, but still deceleration was no where near what it should have been. But thanks to ABS, steering was still in complete control, and thanks to my presence of mind, I used engine breaking to the max and somehow managed to bring the car to a halt.

I tested the brakes several times before rolling off from there, and I am not sure if i can reproduce this to make the Service centre guys understand the issue. I was thinking of Tarox brakes all through yesterday and bumped into this thread right in the morning!
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Old 24th March 2014, 08:44   #49
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Default Re: Strange loss of braking ability. What happened?

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Originally Posted by aravind.anand View Post
OK, last saturday night I experienced the same on my 10,7xx kms run Fiesta 1.6 S. The car decelerated initially, but after a brief moment, brakes just din't feel right! I then stomped on the brakes, ABS cut in, but still deceleration was no where near what it should have been. But thanks to ABS, steering was still in complete control, and thanks to my presence of mind, I used engine breaking to the max and somehow managed to bring the car to a halt.
Were you holding the pedal depressed slightly for a slight amount of time? If ues then they would have got hot causing them to loose of braking efficiency and since your car has ABS, things didn't get serious and they worked well when more force was applied.

Engine braking

Anurag.
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Old 24th March 2014, 09:01   #50
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Default Re: Strange loss of braking ability. What happened?

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Originally Posted by a4anurag View Post
Were you holding the pedal depressed slightly for a slight amount of time? If yes then they would have got hot causing them to loose of braking efficiency and since your car has ABS, things didn't get serious and they worked well when more force was applied.

Engine braking

Anurag.
Yes Anurag, I was braking at probably 60% of the max load before I ran into this situation. But considering that it the car was standing still for two hours before this drive, and that this happened right on the first stretch where I braked hard after the halt, is making it very hard for me to buy into the theory that it could have over heated. As I have had many high speed highway runs with neat braking performance on the same car.
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Old 24th March 2014, 09:04   #51
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Default Re: Strange loss of braking ability. What happened?

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Originally Posted by aravind.anand View Post
Yes Anurag, I was braking at probably 60% of the max load before I ran into this situation. But considering that it the car was standing still for two hours before this drive.
Can I know how 'long' was the distance before you needed the braking power to get the car to halt?

Anurag.
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Old 24th March 2014, 12:38   #52
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Default Re: Strange loss of braking ability. What happened?

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Originally Posted by a4anurag View Post
Can I know how 'long' was the distance before you needed the braking power to get the car to halt?

Anurag.
Not very sure of the distance - as I was in not in a position to measure all that.

But the 60% load application was applied for about 250m at the most. And the car was finally brought to a halt with easily 20-30% longer stopping distance than it would have required normally. The road wasn't even wet, not did it have too much dust or gravel.
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Old 24th March 2014, 17:00   #53
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Originally Posted by aravind.anand View Post

Not very sure of the distance - as I was in not in a position to measure all that.

But the 60% load application was applied for about 250m at the most. And the car was finally brought to a halt with easily 20-30% longer stopping distance than it would have required normally. The road wasn't even wet, not did it have too much dust or gravel.
Get the brakes cleaned once and see of you get to feel any difference.

When was the brake fluid changed? If old then bleed it out and add in fresh oil after removing all air bubbles trapped.

Anurag.

Last edited by aah78 : 25th March 2014 at 01:16. Reason: Post edited on request.
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Old 24th March 2014, 18:27   #54
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Default Re: Strange loss of braking ability. What happened?

Was busy last weekend and hence couldn't get the car checked. Will do it this week.
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Originally Posted by saket77 View Post
PS: from OP's experience, I feel that he might have had a locked up wheel situation. He may not have noticed the sound of the skid due to rolled up windows + AC+ stereo or other reasons, but since he saw skid marks, I think it was a wheel lock up situation.
What I recall is the wheels locked briefly, but started rotating immediately. I remember coming to halt with wheels turning.

Probably the reason for brake going numb is I braked harder than normal. Note that this doesn't happen in all hard braking. The effective way to brake I have found is instead of braking hard all at once, just press the brake to light up brake-light and then in the next instant hit the brakes. Don't touch the clutch. If you do, you won't be using engine braking.
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Old 24th March 2014, 18:33   #55
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Default Re: Strange loss of braking ability. What happened?

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Originally Posted by msdivy View Post
Don't touch the clutch. If you do, you won't be using engine braking.
Obviously. If you hit the clutch simultaneously, you are taking the engine braking out of the equation and at the same time putting a lot of load on the braking system.

However, I tried to repeat what few members tried and replicated in their experiment...I just could not replicate that effect on my car for some reason. Even after pumping brakes as fast as one can, I just could not induce loss of vacuum in the system. In a way, felt good about it.
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Old 24th March 2014, 18:56   #56
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Originally Posted by saket77 View Post
I just could not replicate that effect on my car for some reason. Even after pumping brakes as fast as one can, I just could not induce loss of vacuum in the system. In a way, felt good about it.
But in the WagonR it happened. I did try the same again on my Swift and Ertiga this time but could not get loss of vacuum. Could it be that my car has an ABS module or a better servo booster that will not let the vacuum problem happen?

Anurag.
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Old 24th March 2014, 19:36   #57
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Default Re: Strange loss of braking ability. What happened?

If the brake works initially and then deteriorates it points to over heating of the brake material. This will normally happen on a long highway drive, especially when you are braking and accelerating constantly.

As far as engine braking is concerned on both my Esteem and now my Alto K10, I at times down shift rapidly from 5th to 3rd from 100+, with no ill effect. Mostly this is to overtake, but at times for braking.

Last edited by aah78 : 25th March 2014 at 01:17. Reason: Spell-check. break -> brake.
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Old 24th March 2014, 20:34   #58
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As far as engine braking is concerned on both my Esteem and now my Alto K10, I at times down shift rapidly from 5th to 3rd from 100+, with no ill effect. Mostly this is to overtake, but at times for brakeing.
5th to 3rd from 100 kmph :O

Won't it over-revv the engine? I guess you must be using braking also at that time or only using engine braking?

Anurag.

Last edited by aah78 : 25th March 2014 at 01:17. Reason: Spell-check on quoted post.
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Old 25th March 2014, 08:54   #59
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Default Re: Strange loss of braking ability. What happened?

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Originally Posted by a4anurag View Post
5th to 3rd from 100 kmph :O

Won't it over-revv the engine? I guess you must be using braking also at that time or only using engine braking?

Anurag.
Both the engines can rev upto 6300 RPM, and at 100 in 3rd it is below that mark. In fact I have gone beyond 90 in the second while overtaking on highways.

Personally I have had so many brake failures in my older cars - Ambassador and Fiat, that for the last 25 years I am extremely careful while braking and use the engine braking to the hilt. Once in a while when the traffic is light, I use only the downshift to reduce the speed from 70+ to 20, and this actually works as fast if not faster than using the brake. When a relative's brake had failed completely, I brought it in, driving carefully and using the engine for braking. The final stop was a bit jerky, but the car did stop spot on.
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Old 25th March 2014, 10:36   #60
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Default Re: Strange loss of braking ability. What happened?

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Both the engines can rev upto 6300 RPM, and at 100 in 3rd it is below that mark.
Using engine braking to an extent within a normal range of RPM is acceptable, but by dropping 2 gears down at 100KMPH will put the drivetrain to severe stress which may lead to premature failure. Also, using engine braking at such high speeds will damage the engine and the suspension too. And why to put the engine over so much stress to achieve 90 KMPH in 2nd gear? Due to the high engine braking the gear will offer, the car can go out of control or behave in an unexpected matter even with slight miscalculation while dealing with the A pedal.

Last edited by saket77 : 25th March 2014 at 10:38.
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