Very Quiet Hissing from near brake pedal

vrb · Sep 8th, 2015, 16:29

Dear all,

I have a question.. There is a very quiet hissing coming from the general vicinity of the brake pedal.. It's only noticeable when stereo is off and there is no noise in the cabin.

Everything seems to work fine and there are no error messages on the car display. The strange thing is that the hissing seems to stop when I stick my foot on the brake!

The braking on the car seems to be fine and I was wondering.. Does this sound like a little leak somewhere or is it symptomatic of perhaps a failing brake servo?

I've driven it about 1,000 miles since I started noticing it and the car seems to be fine.. There has been no worsening of the hissing...

I have a warranty with Warranty direct (the secure care one). Is it worth having them have a look.. Brake hoses and other things are not covered but anyone have an idea what a repair would generally cost?

Many thanks

Vince.

CTCNetwork · Sep 8th, 2015, 17:58

Hi,

A hissing would, in my mind, indicate a possible air leak.
The only thing that I can think of that may be driven or run on air will be the heating/cooling distribution box.

It may be worth peeling the carpets back, removing a few panels to further pin point the leak/sound and see if you can find the offending pipe.

Des. . .

Simon Jones · Sep 8th, 2015, 23:30

This was a common symptom on the P2 models and it pointed to a faulty servo which typically costs over £500 to replace due to having to lower the engine slightly to gain access. Whether the P3's suffer the same issue I can't say.

vrb · Sep 9th, 2015, 08:12

Thanks for the replies.. The brake servos are covered under the warranty so if it is that I shall just have to pay the excess.. The car is due it's service and mot in December.. Is it worth having it checked then or is sooner the better?

Model flyer · Sep 9th, 2015, 10:05

If your car is petrol powered the engine can supply a virtually unlimited vacum to the servo all the time it's running. The diesel relies on a vacum pump that will have to work harder to keep the vacum low enough to work your brakes efficiently. Get it checked before if fails.If you ever wondered what effectno vacum has on your brakes try pumping the pedal with engine switched off until it gets a dead feeling then roll the car down a slight slope and try to stop it !!! It is very very hard work . Better get it fixed ,its well worth paying you excess.

dingov70 · Sep 9th, 2015, 12:00

[QUOTE=Model flyer;1976768]If your car is petrol powered the engine can supply a virtually unlimited vacum to the servo all the time it's running. The diesel relies on a vacum pump that will have to work harder to keep the vacum low enough to work your brakes efficiently.

That is not exactly accurate, due to the engine sucking air from the servo , it can /does affect fuelling as modern engines have lambda sensors in exhaust taking oxygen readings . Diesels running a pump will always generate a greater vacuum due to the constant nature of the pumps action , the petrol engine relies of a partially closed throttle to generate a pressure differential after the throttle body and can fluctuate as a result . Due to this petrol engines can become erratic when idling as the ecu attempts to control the fuel/ air fix . So a leaking servo can manifest itself as many problems before it is traced . To the O.P. of this thread , if the engine is not running & you are sat there quietly , you may well hear air leaking back into the servo , it might not actually be faulty , but do get it checked

vrb · Sep 10th, 2015, 07:47

Thanks everyone... Booked in this Saturday for a diagnostic at the local Halfords (Saabena will also be there at the same time for a service and MOT

)... I take it a brake booster is the exact same thing as a brake servo?

Simon Jones · Sep 14th, 2015, 19:57

Best of luck with the Halfords thing. You'll probably end up being flogged a new stereo and some wide wheels.

vrb · Sep 15th, 2015, 11:55

Halfords were fine.. Unfortunately there is a leak in the brake servo.. the warranty company won't cover it as the car is still inside the 90 day wear and tear exclusion period.. Great.. Will have to pay about £650 to get it fixed.. Has to be done I suppose.. Wouldn't like it to go when I really need the brakes to work.

Not so good as the Mrs' Saab which had 2 cracked front springs and failed the MOT...

vrb · Sep 18th, 2015, 10:29

Well that's all done.. 4 hours work in total and the cost of the part.. They did a replacement of the lines and a drain and top up of the fluids whilst the were at it.. Just North of £600....

I had a few quotes and what I was wondering was that most garages said they could only supply Volvo parts as no others were in existence.. A few said that they could get OEM parts which were about £80 cheaper..

All very confusing.. One garage even quoted for 1 hour labour in total which would have been quite impressive.

Anyway the hissing is gone completely and the brake pedal does seem a little bit firmer...

Anyway you live and you learn..

Thanks for all ye help and advise on here..

Sep 8th, 2015, 16:29	#1
vrb Member Last Online: Apr 7th, 2021 08:46 Join Date: Jul 2015 Location: Croydon	Very Quiet Hissing from near brake pedal Dear all, I have a question.. There is a very quiet hissing coming from the general vicinity of the brake pedal.. It's only noticeable when stereo is off and there is no noise in the cabin. Everything seems to work fine and there are no error messages on the car display. The strange thing is that the hissing seems to stop when I stick my foot on the brake! The braking on the car seems to be fine and I was wondering.. Does this sound like a little leak somewhere or is it symptomatic of perhaps a failing brake servo? I've driven it about 1,000 miles since I started noticing it and the car seems to be fine.. There has been no worsening of the hissing... I have a warranty with Warranty direct (the secure care one). Is it worth having them have a look.. Brake hoses and other things are not covered but anyone have an idea what a repair would generally cost? Many thanks Vince.

Sep 8th, 2015, 17:58	#2
CTCNetwork Forum Support Team Join Date: Dec 2004 Location: Liège, Belgium View Photos By: CTCNetwork	Hi, A hissing would, in my mind, indicate a possible air leak. The only thing that I can think of that may be driven or run on air will be the heating/cooling distribution box. It may be worth peeling the carpets back, removing a few panels to further pin point the leak/sound and see if you can find the offending pipe. Des. . . __________________ Density:- Not just a measurement ~ It's a whole way of Life.! ! ! I drive a Volvo, Please Don't Get In My Way! OldVolvos4Ever He shows up. People die. He vanishes. People should not be afraid of their governments. "He'll deliver more justice in a weekend than 10 years of your Governments should be afraid of their people... "V" courts & tribunals. Just stay out of his way." "I plan to." Last edited by CTCNetwork; Sep 8th, 2015 at 23:43.

Sep 9th, 2015, 10:05	#5
Model flyer Master Member Last Online: Dec 15th, 2023 18:46 Join Date: Jan 2006 Location: Kent,pothole capital of UK.	If your car is petrol powered the engine can supply a virtually unlimited vacum to the servo all the time it's running. The diesel relies on a vacum pump that will have to work harder to keep the vacum low enough to work your brakes efficiently. Get it checked before if fails.If you ever wondered what effectno vacum has on your brakes try pumping the pedal with engine switched off until it gets a dead feeling then roll the car down a slight slope and try to stop it !!! It is very very hard work . Better get it fixed ,its well worth paying you excess. __________________ The secret of flight is to aim at the ground and miss ! Previous Volvos 740 GLE . V40 CD ,V70 2.4 SE LPT.V70 D5 P2. V70 D5 Se Lux P3. Current Jaguar XF Sportbrake but still like Volvos

Sep 9th, 2015, 12:00	#6
dingov70 Master Member Last Online: Apr 22nd, 2024 06:42 Join Date: Jan 2015 Location: Blackpool	[QUOTE=Model flyer;1976768]If your car is petrol powered the engine can supply a virtually unlimited vacum to the servo all the time it's running. The diesel relies on a vacum pump that will have to work harder to keep the vacum low enough to work your brakes efficiently. That is not exactly accurate, due to the engine sucking air from the servo , it can /does affect fuelling as modern engines have lambda sensors in exhaust taking oxygen readings . Diesels running a pump will always generate a greater vacuum due to the constant nature of the pumps action , the petrol engine relies of a partially closed throttle to generate a pressure differential after the throttle body and can fluctuate as a result . Due to this petrol engines can become erratic when idling as the ecu attempts to control the fuel/ air fix . So a leaking servo can manifest itself as many problems before it is traced . To the O.P. of this thread , if the engine is not running & you are sat there quietly , you may well hear air leaking back into the servo , it might not actually be faulty , but do get it checked __________________ To stupidity & beyond

Sep 8th, 2015, 23:30	#3
Simon Jones Premier Member Last Online: Jan 15th, 2022 11:23 Join Date: Feb 2009 Location: Salisbury (ish)	This was a common symptom on the P2 models and it pointed to a faulty servo which typically costs over £500 to replace due to having to lower the engine slightly to gain access. Whether the P3's suffer the same issue I can't say.

Sep 9th, 2015, 08:12	#4
vrb Member Last Online: Apr 7th, 2021 08:46 Join Date: Jul 2015 Location: Croydon	Thanks for the replies.. The brake servos are covered under the warranty so if it is that I shall just have to pay the excess.. The car is due it's service and mot in December.. Is it worth having it checked then or is sooner the better?

Sep 10th, 2015, 07:47	#7
vrb Member Last Online: Apr 7th, 2021 08:46 Join Date: Jul 2015 Location: Croydon	Thanks everyone... Booked in this Saturday for a diagnostic at the local Halfords (Saabena will also be there at the same time for a service and MOT )... I take it a brake booster is the exact same thing as a brake servo?

Sep 14th, 2015, 19:57	#8
Simon Jones Premier Member Last Online: Jan 15th, 2022 11:23 Join Date: Feb 2009 Location: Salisbury (ish)	Best of luck with the Halfords thing. You'll probably end up being flogged a new stereo and some wide wheels.

Sep 15th, 2015, 11:55	#9
vrb Member Last Online: Apr 7th, 2021 08:46 Join Date: Jul 2015 Location: Croydon	Halfords were fine.. Unfortunately there is a leak in the brake servo.. the warranty company won't cover it as the car is still inside the 90 day wear and tear exclusion period.. Great.. Will have to pay about £650 to get it fixed.. Has to be done I suppose.. Wouldn't like it to go when I really need the brakes to work. Not so good as the Mrs' Saab which had 2 cracked front springs and failed the MOT...

Sep 18th, 2015, 10:29	#10
vrb Member Last Online: Apr 7th, 2021 08:46 Join Date: Jul 2015 Location: Croydon	Well that's all done.. 4 hours work in total and the cost of the part.. They did a replacement of the lines and a drain and top up of the fluids whilst the were at it.. Just North of £600.... I had a few quotes and what I was wondering was that most garages said they could only supply Volvo parts as no others were in existence.. A few said that they could get OEM parts which were about £80 cheaper.. All very confusing.. One garage even quoted for 1 hour labour in total which would have been quite impressive. Anyway the hissing is gone completely and the brake pedal does seem a little bit firmer... Anyway you live and you learn.. Thanks for all ye help and advise on here..

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