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Yesterday while coming to a stop at a traffic light I know is going to be red for a minute or two I turned off the engine (manual start-stop system in a way), although before coming to a complete stop. A bit after the engine was off I felt a small 'pop' from the brake pedal that I couldn't quite place. As if the brake pedal pushed back against the foot for a bit and then returned to normal.

Now, in the evening and also this morning before starting the car the brake pedal was stiff and didn't move until I turned on the engine, which I've also not encountered before. I can enforce that by pumping the brakes a few times after shutting down the engine, but so far it hasn't been the default state when entering the car after it has been standing for a while.

A bit googling around seemed to suggest that brake pedal resistance to the point of it not moving while the engine is off is perfectly normal. It also gives way as soon as I turn on the engine, so the brake booster is working as intended. I brought the car to a mechanic this morning and they also noted noting out of the ordinary with the brakes (did a short test drive, including emergency stop, brakes work fine).

Which still leaves the popping feeling I'm not really sure what it came from. Well, and that the brake pedal changed its default state from one day to the next. Is there anything I should be worried about or have it checked again somewhere else?

(Škoda Fabia 1.2 l petrol from 2011, has been serviced every year, last time in December.)

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It may as well be that you went over a little rock or bump and it got translated to a bigger feeling because the brake booster was not operating. I wouldn't worry about it since your mechanic thinks everything is OK and car works fine otherwise. The stiffness is very normal. Once you turn off your engine there is still vacuum in the brake booster, but if you press it few times then vacuum is used, so it gets stiff. At least in my car I also can't turn the steering easily when the engine is off (I don't know if yours have electric power steering or vacuum based).

BUT don't turn off your car while moving. Especially never when going downhill etc. You may have steering and brake problems and these usually end in a car crash.

The amount of fuel you save is irrelevant. I have 1.6L 16V VW MK4 and it uses ~0.6l/hour when idling. If I sit in car for 1 hour, idling, it would cost roughly 1 euro. Usually when you stop at a light, it usually takes less than a 30seconds so do the math...

If your car does not have start/stop feature from factory, trying to emulate it may cost more. Because your car was not designed to handle so many start/stops. Maybe you need to change your starter sooner and it costs 100s of euros...

The better ways to save fuel when coming to stop are:

a) Press clutch and let engine idle when slowing down, use brakes to stop.

b) Switch to a lower gear, so you can slow down with engine doing higher RPM without pressing brakes (but use brake when necessary). This way you can save your brakes also :) (in this case, in my car if engine is doing over ~1500rpm, the computer stops sending fuel to it)

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  • In that case I turned it off while going perhaps 5 km/h or less, so shortly before stopping over the last meter or two. Power steering is lost, indeed. I already shift down when slowing down to let the engine do a part of what the brakes would otherwise have to do (I suspect in your last paragraph you actually mean "lower gear"). As for fuel savings, it's pretty much only two traffic lights on my commute that are red for significant amounts of time and the figure I recall was anything above 30 s does save fuel. The wear on the starter or battery from two more starts a day probably don't matter
    – Joey
    Mar 10, 2017 at 11:30
  • Yes, I meant lower gear. But in either case, I wouldn't bother. I still think the savings will be about 1 euro per month, hardly worth the effort. It probably costed more in time to go to mechanic to ask about your brakes etc. already :)
    – Evren Yurtesen
    Mar 10, 2017 at 12:26

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