Team-BHP - Strange loss of braking ability. What happened?

Quote:

Originally Posted by a4anurag (Post 3395978)

Not idle totally but near idle and in gear as I made it sure the engine didn't stall.

Anurag.

But under real driving conditions, the engine would be running at an RPM much higher than idle and hence creating vacuum at a faster rate.

Quote:

Originally Posted by a4anurag (Post 3395962)

:thumbs up

Ok things cleared, just tried the 'BANG' thing now, yes, the brake pedal did get hard when pumped at a very fast rate without much gap in between two pumps.

Anurag.

:thumbs up

Quote:

Originally Posted by saket77 (Post 3395977)

But your engine must be at idle during this experiment, isn't it?

Well I told you to try this out in a parking lot because of the safety point of view. I have tried this out with at 2500 rpm ( Its a diesel) @110 kmph too( On an empty stretch of course) and the result has been more or less the same. You can try it out on an empty stretch of road if you want.

Quote:

Originally Posted by saket77 (Post 3395981)

But under real driving conditions, the engine would be running at an RPM much higher than idle and hence creating vacuum at a faster rate.

In normal driving conditions, you would not pump the pedal this fast as it would be pointless and you would end up unsettling the car if you did this at say 140 kmph.

The fast pedal pumping I am talking about is at the rate of 3 to 4 press releases in less than 2 seconds and no amount of engine rpm will not let the pedal get hard.

Quote:

Originally Posted by humyum (Post 3395847)

Are you pressing the brakes in super rapid succession like 3 to 4 times continuously in a row? Like, Press, release, Press release, press release, press release. Like you know BANG BANG BANG BANG. If so, you are not allowing the vacuum to fill the booster for it to start working again. Happens to every car. You can try it on your friends car too if you want. Go militant with the applying and releasing of the brake pedal and even a completely working broke booster will not fill in vacuum that quick and the brakes will harden up.

The scenario is same as you described - but the frequency is much lesser. Its like press, press release, wait (2 seconds), press, press release, wait( 2 sec),.. and so on.
So i guess even with this time interval of 2-3 seconds, the vacuum is not filling the booster - am i correct?

Quote:

Originally Posted by DCEite (Post 3396016)

Okay, I get you. 2 to 3 seconds is pretty long time for the booster to replenish. Try this as I mentioned earlier. Park the car in the night and when you are about to go to work tomorrow morning, without starting the car hit the brake pedal. Check if its rock hard or if its soft for a couple of hits after which it becomes hard.

If its hard right from the first hit, the booster is leaking and needs a change.

If its soft for a couple of hits and then gets hard, I suggest first to test drive another Spark and check if its the same issue. If it is, its a manufacturing fault as some years back people had reported it in the Swift where in at idle speeds the pedal would get hard after a push or two of the brake pedal. I remember Maruti did a software tweak where in the idle rpm would not fall below a certain RPM to maintain the level of vacuum in the booster.

If the other Spark does not have the issue that you have, the vacuum lines and check valve will need to be inspected.

Quote:

Originally Posted by DCEite (Post 3396016)

I agree with Humyum sir here,

But otherwise how is the braking and feel normally without any kind of emergency braking?

Anurag.

Could be braking on sand/mud/gravel.
The wheels would lock easily and you may not hear anything in the car with the stereo on.
However, this would leave a clear mark in the sand/mud if you stop and inspect.
Also the fact that the car got its braking bite back later sounds like the car cleared the patch before the junction.

Quote:

Originally Posted by Leop (Post 3396038)

Could be braking on sand/mud/gravel.
The wheels would lock easily and you may not hear anything in the car with the stereo on.

However, this would leave a clear mark in the sand/mud if you stop and inspect.
Also the fact that the car got its braking bite back later sounds like the car cleared the patch before the junction.

I don't think the stereo will be deafeningly loud for the driver not to realize the skidding over gravel/mud.

May be the booster could be the problem as it could not get back into work when braking was needed but later was OK when the car came to stop.

Anurag.

Is engine braking good at a speed of 90 to 100 kmph, which was the speed in the first post? If yes, should one downshift to 4th or 3rd? I know 2nd would make the car hit the rev limiter and screw up the engine by over-revving.

I guess the answer might differ from car to car. When I drop from 4th or 5th to 3rd on my petrol Fiesta at a speed of 60 kmph, the tacho shoots up from around 2000 to nearly 3500 to 4000, which is well within the redline of 6000. But at a speed of 90 or 100, I am apprehensive that it will hit the rev limiter, but I may be wrong.

Quote:

Originally Posted by vnabhi (Post 3396088)

In 5th gear at 100 kmph the RPM would be around 2.3K if it is a diesel and around ~3K in a petrol. Downshifting to 4th gear here would not be advisable. 3rd and 2nd are ruled out anyway as the engine will fry. :)

Downshifting is best when speeds reach near 70kmph @ 5th great to 4th.

Anurag.

Quote:

Originally Posted by humyum (Post 3395847)

In a diesel, yes. But should not be a problem in a petrol. Have to physicall check it out.

Regards
Sutripta

Possible causes:

Engine Idle was below required level at that point of time. This will not provide enough power to engage the brake which feels hard with no effect on brake. I faced this issue with my old ZEN

If the car is loaded chances of brakes getting heated increases dramatically, which causes the same issue of losing brakes. Heat builds up each time you apply brake especially at high speed. At a point the heat might reach a point where brakes are not effective. I faced this issue with my Swift once.

Having graduated from a jeep to a bolero, both vehicles (in)famous for their brakes,I have learnt to brake by pumping on the pedal.Its a matter of habit and we can learn to brake by pumping the brakes no matter wherever we are driving.I feel, by pumping ,one can give the pads a bit of respite so that the bite would be better.

As for the loss of braking power ,i have experienced it often over the years and all the causes mentioned by T-BHP members have been probed for .But so far have never been able to pinpoint, that because of one particular reason the brakes failed.

Brakes are the most important component in a vehicle IMO and I make it a point to get it checked first whenever the vehicle is serviced.The necesary oil levels,brake pads,line leakeages etc , have been checked but every once in a while the brakes do give my heart a small jolt.

I feel a car being a mechanical/electrical component,one part or the other might have given off for a brief moment .It might be a nanosecond system crash but the system kinda recovers if i might say so.One just has to be careful and keep all the senses alert.

Hi,
My 2 cents:
1. Let us not doubt the tyres unless roads were wet. For 2006 City's weight and the speed+tarmac you have mentioned 185 section rubber first of all would not slip at all! Still if it does, then such significant braking force and subsequent would lead to loss of traction too (which you have not mentioned).
2. First point - get your Liners (front) , Pads (rear) cleaned or replaced if needed. Also, get the lines bled and fill in recommended Brake Oil.
3. Next point - Check the servo.
4. Though very scarce, but a prolonged run with less than low level of Brake Oil would result in Damage to Disk itself due to overheating.
Please make sure this all must be done in HONDA After Sales Service Centre.

Hope it helps!

Quote:

Originally Posted by Zinda (Post 3396423)

4. Though very scarce, but a prolonged run with less than low level of Brake Oil would result in Damage to Disk itself due to overheating.

How low a level of brake fluid are we talking about? The brakes are still operational, right?

Regards
Sutripta