Hi,
I have bought a Mondeo 2.0 TDCI Zetec in the last few days and last night I started to notice the following issue:
1) I turn the engine on
2) When I press the brake pedal I can hear air being released (while the pedal is going down, not once it stops moving)
3) I turn the engine off
4) I press the brake again a few times and hear air then it stops and the pedal stiffens up (so that it hardly presses down)
5) If I restart the engine I hear air again when I press the pedal
Does that sound normal? I had never noticed it before, but because I have only had the car a few days, I am still getting used to what is normal.
I posted this question at the end of an unrelated thread, and Altea Ego kindly responded explaining that this is normal on some cars.
www.honestjohn.co.uk/forum/post/index.htm?f=2&t=78...2
I just wanted to double check that it is normal on Mk 4 Mondeos, because I am obviously keen to be doubly sure that the brakes are OK :) To this end, I have also posted the same question here:
www.fordmondeo.org/forum/showtopic.php?tid/817261/
Any further help would be greatly appreciated.
Many thanks
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i have one so will endeavour to check at lunch time for you.
Cant say i have ever noticed it though. Doesnt mean it doesnt do it!
Good cars arent they.
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i have one so will endeavour to check at lunch time for you.
Thanks. Much appreciated.
Good cars arent they.
Yeah, I am really happy with it so far. I'm still getting used to the size of it, but it seems like a nice ride.
Thanks again.
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Stage 4) is entirely normal for cars with servo brakes. Not owning a Mondeo I do not know about the other points.
Edited by Glaikit Wee Scunner {P} on 23/09/2009 at 10:24
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What's happening here is that the brake servo is having air pumped out of it ("filled" with a vacuum, you could say!) such that the brakes can be assisted. When you turn off the engine this vacuum remains, once you press the pedal a few times the vacuum will be "used".
It's there to provide a reserve of vacuum for emergencies such as when your engine cuts out and you need to stop.
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>>What's happening here is that the brake servo is having air pumped out of it
Actually, almost the opposite is happening.
With the engine running, and for a time after it has stopped, until the brake pedal is pressed, there is vacuum on both sides of the diaphragm in the so-called suspended vacuum servo, and both sides of the diaphragm are open to each other.
As the pedal is pressed, this connection between the front and the back of the diaphragm is first closed.
Then, as pedal pressure increases, atmospheric air enters via a sponge filter which surrounds the brake pedal pushrod. It is this atmospheric air which the OP may be hearing, which is quite nortmal, and it is the pressure difference between the atmospheric air on one side, and the engine vacuum on the other side of the diaphragm which provides the brake assistance.
It is possible for the inter-connection valve to fail to seal fully , and this could provide exaclty the symptoms described by the OP. It is difficult to tell without hearing the servo and feeling what assistance it provides, whether the noise heard by the OP is the normal action of the atmospheric valve, or the inter-connecting valve failing to fully seat.
During a moderate brake application, the forces balance, and the atmospheric valve closes again - which would mask a leaking inter-connecting valve.
If, with the engine running, and the foot pressed *really* hard on the pedal (such that the atmospheric valve is kept wide open), the noise persists, there is a problem with the inter-connecting valve. If, however, the noise stops after the atmospheric air has entered the servo, then, all is well.
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You are conducting the approved test for brake servo operation and your car has passed! That's called serendipity.
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Or it could be a lorry parked behind you :)
Pat
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Have tested this for you and mine is the same. It's a bit like a puff of air as you press (suspect it is some sort of damper for the pedal rather than a part of the brake system) didn't notice it when driving normally
the other characteristic is also normal, all cars I've had with"assisted" brakes have done the same.
Hope that puts your mind at ease
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SQ
Hope that puts your mind at ease
Hi. Thanks for taking the time to do that, I really appreciate it.
I actually took a video of the pedal doing it, and have literally just uploaded it here:
www.youtube.com/watch?v=Kgf2hvwkN2U
From what you say it sounds exactly like the noise you are getting.
Thanks again.
Edited by Dynamic Dave on 24/09/2009 at 02:06
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That sounds quite normal - it's just the atmospheric pressure being admitted as described.
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Another reason for the petrol version then, wouldn't have heard it over the deafening clattering of the oil burner..;)
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Never mind the noise, where did you get your 'driving shoes' from? ;>)
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cant hear the noise being made as harry chapin is on the hi fi
however i would get rid of the rat in the footwell as no good will come of it
trust me on this one
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Never mind the noise where did you get your 'driving shoes' from? ;>)
Them shoes is wikkid, man.
But never mind where he got them. I want to know why he's wearing them inside-out
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Them shoes is wikkid man. But never mind where he got them. I want to know why he's wearing them inside-out
LOL. I was worried that everyone would mock my scuffed up shoes. I should have realised they would mock my inside-out socks even more! :)
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