Xantia 90Hdi. Really frustrating noise; any ideas?

[rmunns]

This is driving me nuts. Please can someone help?

I've had the (90Hdi saloon, year 2000) for 16 months. It was a one-owner car when I got it and it had full service history with 38000miles.

Since June 2009 I've done 20000 miles. All I've done is to fit new tyres, new front discs and pads and change oil / filter.

For about a year I've had this noise on-and-off. It's now started to happen more often and has become more intrusive. Particularly today.

The noise has no links to the tyre or the new brakes. It was there before they were fitted.

It is a constant-pitch drumming / throbbing noise. Very like a fan. But it is certainly not the radiator fans nor the heater fan. It has on occasion come on as soon as the car is started but more normally you notice it when you are idling during a journey. It can come and go during a journey.

The noise is constant pitch. No change if the clutch is dipped and the engine revs blipped. And it is there when you are idling at lights - i.e. not road-speed dependent.

It really does not add up.

It's spoiling my enjoyment of what has been a brilliant, economic car. I'm so apprehensive that something critical might be imminent. And I can't afford that.

[Toby_HDi]

I wonder if it is the early signs of the infamous lift pump failure? Does it ever do it with the ignition on but the engine not started?

[rmunns]

No.
And when I turn engine off, with noise present, it stops instantly, before engine.

[addo]

I'd say it is one of the motor mounts either hardening or failing with age.

Other than that, look for exhaust brushing the body somewhere.

[RichardW]

It's the fuel filter - as I'm sure I've said before..... Try the screwdriver / ear trick on it to pin it down. Change it complete and the noise will almost certainly go away - it has on mine. I got one from GSF for £55 delivered (UK) and it only takes about 20 minutes to change it (although it's a pretty mucky job).

Thanks to the helpful link Paul posted the other day I now understand the internals - there is a bimetallic strip on the inlet which diverts the fuel either direct into the filter or via the thermostat housing depending on the fuel temp. My guess is that this gets a bit weak, or gets a bit of crap around it, and vibrates rather than directing the flow one way or another.

It is possible that the LP pump is playing a part, and changing the filter may not totally cure it - but it is cheaper than the pump, and if it's not been changed in a while then it's no loss to fit a new one. Mine had not been changed in the time I'd had it (er 60k miles....!) and no idea when it was changed before that. It was pretty manky inside!

[VertVega]

... But it is certainly not the radiator fans nor the heater fan...

Just reminds me of the dry leaves parts or pine wood needle kind of material in the heater fan but you already said that it is not heater fan.
But still, just in case ... While idling (and radio off) move the heater slider from 'Automatic' to 'Small fan' position and listen if there is any change in the noise. Then gradually slider to max speed position and listen if there are any changes.

Second option could it be the small fan of the cabin temperature sensor which is next to the clock, behind the small grill. Some air pressure would clean it.

Is the noise coming more from front or rear? Inside the car or from engine bay. I understand how annoying such little noises can be.

[rmunns]

Thanks to you all for the suggestions, I'll look into them. The noise is front-end, under the bonnet, but with the bonnet up the engine noise makes it hard to hear the phantom noise. From inside the car it is quite noticeable to the driver (RHD car) but from the passenger seat it can't really be heard.

I've tried all heater fan settings and changing them has no effect on the noise.

The service book says the fuel filter was changed @ 36k (now 58k). I have a new one (internals - your comment seems to infer you change the whole canister?) so I could try that.

Does changing the fuel filter internals have any difficulty or snags attached?

Thanks again.

[RichardW]

Yes, you need to change the whole canister. Just changing the element won't get to the problem area. There are some difficulties with changing the element only - all the crap drops into the sump inthe bottom, which is then onthe clean side, so you need to make sure you clean it out well!

If you get a mechanics stethoscope (OK, a long screwdriver or piece of wood held to your ear!) you should be able to tell if the noise is coming from the filter unit or not. It may be though that the vibration is manifesting itself in the pipes under the car.

[DickieG]

If the above suggestions don't sort it out check the exhaust downpipe where it passes over a cross strut brace, if the exhaust isn't original Citroen or mounted incorrectly it can rub against the brace and make quite an annoying racket.

[Dannyboy]

I have the same problem, exactly as described, on a `01 110 Xantia 2.0 HDI with 172 K. It is annoying but I can live with it . Is there any risk to reliability if I ignore it ? ...rgds Dannyboy

[rmunns]

Dannyboy; all I can add is that I've had the noise for a year, on-and-off. It is there more often than not, but today, for example, from cold I drove 15 miles - noise came after about 5 miles. Car then parked for one hour, noise there when starting but gone when I got home.

I really can't imagine it's engine mounts, noise is unchanging when you are totally stationary, idling. Just like a slightly noisy electric motor.

[Citroenmad]

If you listen under the bonnet when the noise is happening can you not pinpoint the area it comes from? Or does the engine drown out the noise?

[rmunns]

Noise is drowned out.

<<<<<<<Sorry to all those reading about this (unsolved) mystery time and again>>>>>>>

[DickieG]

Bit of a long shot but as its easy to check is it the little fan motor behind the alarm LED which draws cabin air across the A/C thermostat?

[rmunns]

DickieG, where is this? Is it in the temperature sensor window in the centre of dashboard?