Hissing noise behind dashboard? Xantia 1.9TD

XantiaMan · Unread post by **XantiaMan** » 15 Jan 2008, 16:21

This afternoon i noticed a hissing noise from behind my dashboard. It is hard to tell if i have lost performance, as the atmospheric pressure is so low at the moment (978 MB) that its dropped anyway, i have not had my heater on hot today and i noticed the hissing noise seemed less? Is the heater actuated by vacuum pipes?

I had a quick check of the boost pipes, all seemed ok but one bolt on the compressor outlet was starting to work loose, i spent 45 minutes trying to tighten up this bolt using my new halfords flexy spanner and eventually, got it nipped up! However it did not solve the problem!

Has anyone else noticed hissing coming from behind the dashboard?

Gareth

jgra1 · Unread post by **jgra1** » 15 Jan 2008, 16:34

my turbo pipework makes a great hiss noise on boost .. I haven't had time to find out where from yet, almost like it tho.

. may be a difffernt noise/problem

Unread post by **CitroJim** » 15 Jan 2008, 16:34

Hi Gareth,

It is not unusual to hear the odd hiss from the steering but normally only when approaching full lock.

If the turbo or truniking is leaky, it's normally more of a whistle.

No, the heater is not vacuum operated but what is though is your fast idle control and your EGR valve. It's worth checking the pipework from the vacuum pump on the end of the cam to the idle and EGR electrovalves up on the bulkhead and on to the idle diaphragm and EGR valve. A perish or hole anywhere in these pipes will make a nice hiss.

Another slight possibility is an LHM leak near the reservior, steering pinion valve or the brake doseur but for a hiss to be heard, that would be accompanied by a fair LHM leak.

XantiaMan · Unread post by **XantiaMan** » 15 Jan 2008, 16:49

Seems odd that the noise is less when the heater is on hot

If i had a boost gauge i could pin point it down to that but i honestly dont think it is the boost, as performance apart from the poor air pressure and high humidity seems unaffected.

My EGR was disabled since i got the car, i've run out of light now but i will have a closer look at the pipes soon, tomorrow i may not notice any noise!

Unread post by **aerodynamica** » 15 Jan 2008, 17:33

Slightly off topic; I have 973mb here on 3 different digital barometers - I was interested in your comment above relating to performance. Is low atmospheric pressure enough to cause lower engine efficiency? I thought it had to be much lower to cause differences - like when you're driving through the Alps or something!

XantiaMan · Unread post by **XantiaMan** » 15 Jan 2008, 18:23

aerodynamica wrote:Slightly off topic; I have 973mb here on 3 different digital barometers - I was interested in your comment above relating to performance. Is low atmospheric pressure enough to cause lower engine efficiency? I thought it had to be much lower to cause differences - like when you're driving through the Alps or something!

I think so. Pressure is very low at the moment because of the weather systems we are having. It's now 976mb on my weather station, the lowest i have recorded to date.

Car seems to have lost some of its verve although i have been driving through torrential rain on the M25 today and it would not surprise me if the air filter was damp to some degree, that alone would cause a difference and it could even be the source of my noise (turbo drawing harder on the air filter?) might check that aswell tomorrow.

Unread post by **aerodynamica** » 15 Jan 2008, 22:39

Well maybe give it some time and it might just go away

My 1977 CX sometimes makes a phenomenally annoying BUZZZZZZ from the instraments at 60mph and at 3.5K rpm and only ever with these two factors together. Crank up the tunes and it can still be heard such is its mad frequency. I guess something in the engine and something on the drive are matching phase at that point and driving me nuts

jeremy · Unread post by **jeremy** » 15 Jan 2008, 22:43

Don't the Xantias have a small electric fan to blow air from the cabin over the temperature sensor? - Is this the source of the noise?

There are some postings on this subject way back.

Unread post by **RichardW** » 16 Jan 2008, 07:55

978mbar? You're not trying hard enough - mine was reading below 948 yesterday

(190m ASL) No appreciable change in performance on our ZX TD.

If the hissing noise is turbo related then it will only come in above 2k rpm and take a few moments to build after you press the throttle. Classic place for the boost to leak is the small hose from the air duct to the injecion pump - and this leads to distinctly flat performance.

Have you got the A/C on? (or in a MK2 got it set to demist, which swtiches the A/C on). In my MK1 there was a distinct hissing noise when the A/C was on and the gas low.

mezuk04a · Unread post by **mezuk04a** » 16 Jan 2008, 07:59

I was thinking the exact same thing last night Jeremy as I had the same when I first got the Xantia, everyone was talking about mechnical things so I thought I best stay stum

XantiaMan · Unread post by **XantiaMan** » 16 Jan 2008, 08:31

RichardW wrote:978mbar? You're not trying hard enough - mine was reading below 948 yesterday (190m ASL) No appreciable change in performance on our ZX TD.

Have you got the A/C on? (or in a MK2 got it set to demist, which swtiches the A/C on). In my MK1 there was a distinct hissing noise when the A/C was on and the gas low.

I've had the air-con alot today to help with demisting so it could be gas getting low, i've not checked it since the summer months and have a can of gas so i'll top it up when i finish work.

Air filter was definatly damp.. a bit dirty too, but it has done 7k. I'll be changing it shortly.

The pipe from the pump to the boost pipe has split twice before and its now been properly replaced, its all in good order and performance is not 'that' off, i'll just put it down to it being a bit too damp!

The noise you could hear from about 1500rpm even on a tiny 'throttle' opening, its not the air temp fan inside as thats a completely difference noise (which i occasionaly get!)

Gareth

Ciaran · Unread post by **Ciaran** » 19 Jan 2008, 17:07

Leaky heater matrix a possibility?

jgra1 · Unread post by **jgra1** » 19 Jan 2008, 17:38

hi Gareth,.,. no help to you but mine turns out to be from tailpipe/exhaust - on boost.. much more obvious now interior removed.. great noise tho

wonder if the turbo on way out...

Unread post by **CitroJim** » 19 Jan 2008, 17:53

Ciaran wrote:Leaky heater matrix a possibility?

Please take very great care when using the words "heater" and "matrix" in the same sentence on this forum. We're a sensitive bunch, us Xantia owners, and easily distressed....

XantiaMan · Unread post by **XantiaMan** » 19 Jan 2008, 18:03

It's not making the noise now! All seems fine.