Brake pedal pressure to start the car

[taylora]

Not sure if I have an issue with the brakes on my V90 D4...

If the car has been sitting for a while, say overnight, I have to press REALLY hard on the brake pedal to get it to start up. When it has been sitting for a short while then just a light tap is enough to convince the car that I'm in the driver's seat and it should start up when I twist the starter control.

I know the vacuum will lose pressure over time but it does take a really firm push if the car hasn't been used for a while.

Is it the same for everyone else?

Another strange thing is I get a bit of a rattling sound when I release the brakes and the autohold is active and holding the car stationary for a second or two. When the pilot assist is active in queuing traffic, again I get a bit of noise and rattling from what sounds like a noisy servo or valve behind the dash somewhere.

Not sure if the two issues are linked and I maybe have a leaky valve or master cylinder.

Be good to know if this is normal behaviour to set my mind at rest. I don't mind the mechanical noises if they are meant to be.

Thanks.

[Philip Fisher]

Originally Posted by taylora

Not sure if I have an issue with the brakes on my V90 D4...

If the car has been sitting for a while, say overnight, I have to press REALLY hard on the brake pedal to get it to start up. When it has been sitting for a short while then just a light tap is enough to convince the car that I'm in the driver's seat and it should start up when I twist the starter control.

I know the vacuum will lose pressure over time but it does take a really firm push if the car hasn't been used for a while.

Is it the same for everyone else?

Another strange thing is I get a bit of a rattling sound when I release the brakes and the autohold is active and holding the car stationary for a second or two. When the pilot assist is active in queuing traffic, again I get a bit of noise and rattling from what sounds like a noisy servo or valve behind the dash somewhere.

Not sure if the two issues are linked and I maybe have a leaky valve or master cylinder.

Be good to know if this is normal behaviour to set my mind at rest. I don't mind the mechanical noises if they are meant to be.

Thanks.

My XC90 should be basically the same set up as your car. This is not normal for me. A light press and the car boots up straight away. It has done so consistently for the last 63k miles.

Imight be wrong but I think that it works on a switch to see if you have the brakes on or not. Perhaps your switch is loose? Do the brakelights work as normal? When you say 'firm push' are you pressing the brake pedal just harder, or is it going further down too?

[Quacker]

As mentioned above, all 90 series cars should be the same and I've not had this issue with mine.

Not sure how Volvo manage this interlock. Whether they use a brake line pressure sensor or, more likely, either a top of brake switch or share with brake light actuation. Any which way apart from the first option, I can't see the other two options having any effect on the safety-start interlock.

[bobby2000]

Originally Posted by taylora

Not sure if I have an issue with the brakes on my V90 D4...

If the car has been sitting for a while, say overnight, I have to press REALLY hard on the brake pedal to get it to start up. When it has been sitting for a short while then just a light tap is enough to convince the car that I'm in the driver's seat and it should start up when I twist the starter control.

I know the vacuum will lose pressure over time but it does take a really firm push if the car hasn't been used for a while.

Is it the same for everyone else?

Another strange thing is I get a bit of a rattling sound when I release the brakes and the autohold is active and holding the car stationary for a second or two. When the pilot assist is active in queuing traffic, again I get a bit of noise and rattling from what sounds like a noisy servo or valve behind the dash somewhere.

Not sure if the two issues are linked and I maybe have a leaky valve or master cylinder.

Be good to know if this is normal behaviour to set my mind at rest. I don't mind the mechanical noises if they are meant to be.

Thanks.

I have the same problem if my car is stood up for several days, it seems to lose pressure and I really need to put a lot of pressure on the pedal to start it. My previous XC60 used to do the same so I thought it must be a Volvo thing.
I don't really want my car to spend a week or more in the dealers waiting for something that might not happen, although I will mention it at its yearly service.

[NickV90]

I get the same rattle in autohold. Almost like someone pinging a ruler on the edge of a desk.

But no issues on starting. Light pressure even after leaving the car for 2 weeks.

[Chief inspector]

I’m holding the brake so it doesnt move when I start it, not tickling it to make a switch, so Ive no idea how hard I’m pushing it, other than with reasonable force.

[gaby]

Originally Posted by bobby2000

I have the same problem if my car is stood up for several days, it seems to lose pressure and I really need to put a lot of pressure on the pedal to start it.

I also need to press harder if the car stood still for a longer period.
But as I feel it, the resistance is higher, as if the hydraulic is locked up or the boost is gone.
If the pedal needs to be pressed down a fixed amount to activate a switch,
that could then be why one needs to press harder.

[bobby2000]

Originally Posted by gaby

I also need to press harder if the car stood still for a longer period.
But as I feel it, the resistance is higher, as if the hydraulic is locked up or the boost is gone.
If the pedal needs to be pressed down a fixed amount to activate a switch,
that could then be why one needs to press harder.

I'm pretty sure it's not a switch problem, more a servo losing pressure over a period of time.
If you pump the brakes enough times with the engine off you will get the same affect.

[MaDProFF]

Very little brake pressure required on my XC60 to start the car, intact pretty well only just have the foot on the brake