Noise Quiz: I name that Tune in...

Dommo · Post by **Dommo** » 08 Feb 2010, 11:13

Looks like the EGR electrovalve on the servicebox..

Part number 1

boristhespie · Post by **boristhespie** » 08 Feb 2010, 14:00

What does it do and how important is it. Is it cheap to replace?

Post by **myglaren** » 27 May 2010, 17:47

Interestingly enough I may have a solution

On returning home this evening I decided to look under the bonnet to see how easy - or not - it would be to pull the leads off the reversing light switch and stick a nail in them to test the reversing light.

While I was peering into the gloom (no, didn't remove anything) i heard a similar "angry bee" sort of noise from around the same area that you indicate.
I was the aircon/ventilation flaps closing. Went on for a fair while, not as loud as yours but in the right location.

Perhaps one of the motors is stuck on, or the flaps jammed and the motor constantly trying to shift it? won't do it much good in the long run if it is.
Does the aircon/ventilation work as it should?

ED: Damnit, Dommo's post wasn't there when I started scribbling

boristhespie · Post by **boristhespie** » 27 May 2010, 19:44

YEah aircon works. It is this part though making the noise I put screw driver on it and it buzzes. The garage owner who did my head gasket felt it last night and he said he could feel it vibrating. Not sure what it is. I did ask the garage today to check it but no mention and I forgot to ask.

coastline taxis · Post by **coastline taxis** » 27 May 2010, 20:38

Turbo boost solenoid. Take them off and shake them if they rattle then there ok if they dont then there goosed. If there ok then check the vacum pipes and wiring to it

boristhespie · Post by **boristhespie** » 27 May 2010, 21:56

Are they dangerous in soe much as they could lead to something nasty?

coastline taxis · Post by **coastline taxis** » 27 May 2010, 22:57

Nope just make the car slugish and turbo will not cut in properly. mpg will be down aswell

boristhespie · Post by **boristhespie** » 28 May 2010, 07:16

I am complete NON mechanical. I need someone to show me before I am confident doing something. After which I am okay.

Could I replace this myself, easily?

KevMayer · Post by **KevMayer** » 29 May 2010, 20:14

Those vacuum solenoid valves are controlled by a modulated DC, so, the sound could be the coil of the solenoid humming with whatever may be being applied to it in terms on a modulated square wave of 12V DC.

Just like the humming of an electrovalve on a hydractive Xantia.

boristhespie · Post by **boristhespie** » 30 May 2010, 16:34

Eh?!

Did you read my above post? LOL

KevMayer · Post by **KevMayer** » 30 May 2010, 17:18

Sorry about that, When you said you're NON mechanical I thought that you must be electrical.. LOL

What I'm trying to describe is a method of getting a voltage which is variable from a fixed 12 V battery/alternator.

See if this makes sense:-

If you put full battery volts onto a component then thats 12 Volts.

Now, if you have an electronic board which switches the volts on for say 1 second and then off for 1 sec then back on and off and on repeatedly then that means you get an average of 6 volts applied. i.e. 12v for 1 sec and zero for 1 sec gives average of 6 volts over the 2 seconds.

If you switch on for 1 sec and off for 3 secs and then on and off for the same period over and over , you get an average of 3 volts i.e. a quarter of the full volts.

The control solenoids on the C5 engine are controlled in this way to change them from fully open to partly open or fully closed, but, the switching is much faster than 1 sec at a time.

So, your buzzing solenoid is probably receiving a quickly switched 12 volts to achieve a much lower average voltage and this choppy supply is probably causing it to buzzzzzz.

Your solenoid may not be faulty at all, it could just be noisy. The electrovalves on the Xantia buzzz like this because once they're switched at 12 volts the electronic control then chops the 12 v to give an average of 3 volts to hold the electrovalves in the on position.

boristhespie · Post by **boristhespie** » 30 May 2010, 22:47

Good explanation.

My turbo seems okay.

I will say though that the Buzz has gotten significantly louder and is constant now.

Car going into garage for height sensors tomorrow so may ask them to have a shifty.

Incidentally you can physically feel the buzz.

KevMayer · Post by **KevMayer** » 31 May 2010, 09:37

Just had a thought about these solenoids.. They must need a diode to release the energy stored in the coil when the DC is switched off.

The problem could be that the diode on your noisy solenoid has failed.

On the Xantia electrovalves a standard mod is to fit a new diode.

It's probably going to be easier to just change the solenoid.

It would be interesting to see if a diode mod would work.

boristhespie · Post by **boristhespie** » 31 May 2010, 21:05

Are the simple to replace. Ie unscrew when car's off (technical I know) and replace with new and that's it or more convoluted?

The garage asked if I wanted them to put car on computer to see if there is anything wrong with them.. LAst time I said yes it cost me 80 quid for nothing.

The dealer put it on the lexia but never mentioned anything other than height adjusters. What should I do say yay or nay?

KevMayer · Post by **KevMayer** » 31 May 2010, 21:39

If the solenoid has just suddenly started to make a noticable noise then If it were mine I'd order a new one and go for changing it. It should be easy, probably a retaining screw and a clip on the electrical plug on connector. This will be the cheapest option.

If it's been making a noise for a while but you've only just noticed, then, if your C5 is running ok i'd leave it alone.

If you believe the solenoid is faulty then go for a change.

I've always been dissapointed with a dealer using a Lexia on my car. I've come to the conclusion that dealers are only good at selling cars.