unknown fan noise - 406HDI 2.0 (YR 2000)

[pugface406lx]

Hi there,

I know this sounds weird but my 406 HDI has a strange fan humming sound from inside the cabin (Forward in the dash area) which I cannot fathom!
I checked the radiator fan and at the time that wasnt running so Im confused as to what it is??
Anyone know what it is?

Regards
puggy

[lozz]

all the 406s ive had have done the same,
does it sound like the noise is coming from the driverside dash area ?

if so check the solenoids on the bulk head, the ones for the egr etc, theyre mounted on aplate with rubber mounts
ijust tighten the 10mm bolts up and noise disapears

[rwb]

Could it be the climate control temperature sensor fan up in the interior light?

[pugface406lx]

Hello everyone, ive found where the noise is coming from, its gotten worse, noticed it when I first turned ignition on without engine running, It buzzed loudly like an electric motor so i managed to get under the bonnet before it stopped, Its coming from a black cylindrical item about the size of a man's fist ....Its at the front of the engine just under engine cover height almost mid way across the car, totally visible and sat on a bracket of its own i think.....i would liken it to a brake reservoir type bottle but its got an electrical buzzing very loud coming from it which sometimes stops after a bit but just lately seems to be on all the time when i drive off!

Not sure if its a fuel pump perhaps??? any ideas?....im not too good on diesels!

Cheers
Puggy

[Welly]

I know what this is.

When you put the car to ignition the fuel pump in the tank pumps fuel through the fuel filter housing (this is the black thing you described) the noise is the fuel passing through the system and it 'sings' as it does. It does this for approx 5 seconds.

What you are hearing is a sympathetic reproduction of the fuel pump's noise which shows itself in that plastic housing.

In cold weather the noise is louder because the fuel takes a detour through some thermostatic valve (which I could never locate) causing a restriction this pre-heats the fuel via the thermostat housing as I recall. The fuel is thermostatically controlled at 25deg C.

[puggy]

[pugface406lx]

Hi Gary,

Yes i think it is what you said...the fuel filter housing vibrates and buzzes like ive never heard before...very loud though too! Is there anything i can do to stop this noise?
ive got a second car identical and it doesnt do this .....in fact on ignition start up as u say it sings as the fuel is being pumped up ready to be fired!
I dont hink I can put up with this noise as it seems to be on all the time the engine is running now .

cheers,
Puggy

[steve_earwig]

I guess your housing is a Bosch (hexagon on the top) I have a Mahle which used to make quite a racket, I even got another housing off ebay and then the mechanic here spotted a connector that was off on it, turns out to be the fuel temperature sensor (and what I jackass I felt too - I thought it was spare for the water-in-fuel sensor, which my car doesn't have). Much quieter now, although still makes a fair bit of noise.

If yours is the Bosch then it doesn't appear to have this sensor, I0m fairly sure there are some valves in it and maybe one of these is chattering so I can only suggest to change it.

[pugface406lx]

Hi Steve,

yes it is a bosch fuel filter housing as you say.....do you think then that there are some valves in there besides the filter itself then? The noise now is very loud like a vibrating drill!!
Someone suggested simply changing the filter but it sounds a bit of a longshot...what do you think?

cheers
puggy

[steve_earwig]

Without one to look at I don't really know. I think the filter on that has some strange seals on the top of it, if one of them's not sitting right maybe the fuel's blowing past it making a noise Might be worth changing it, just in case.

[lozz]

When was the filter last changed ?
if its not recent, for what they cost iwouid buy one and replace it,

idrain them on hdis now and again, to prevent water build up