Quote:
Originally Posted by chinners
Hi - I was wondering if any technical experts could tell me what's going on here and whether these 2 (unrelated) noises are normal - the car is a 2.5 V6 Conn SE auto: - When pulling away from cold, I hear a sort of mild 'thunk' come from the front. It only happens when cold and only the once. I did read about some sort of flap somewhere (manifold?) and was wondering if this is it opening. And what the hell does it do?! Or is it something else?
- Growling - when the ATC is on, there is a low growl, noticeable at lower speeds. If ticking over, the growl is still there, but it gradually fades away until I can no longer hear it. Then as soon as I make off again it comes back. If I come to a stop it is still there, then fades again after 15-20 secs (rinse and repeat). This is not the fan, which I can hear cutting in at slow speeds - it is a separate issue but related to ac, because if I select ECON on ATC, the noise disappears. I can't imagine this noise is normal as it is noticeable - but perhaps it is normal? The ac by the way performs nice and cool - probably the coolest ac I have ever experienced in a car and lovely in the summer heat.
Just wondering if anyone can shed light on any of those. Is my car going to explode or are these 'character traits'? I did search for 'noise' but did not come up with anything that really matched these issues.
Many thanks, Mark |
Hi Mark,
First I am not a tech expert
But
1/ If you leave the A/c on Auto all the time (so that it comes on with the ignition switch) then the A/c compressor will kick in shortly after you start. This is probably the clunck. When the compressor kicks in the engine cooling fan should follow shortly after to cool the compressor. Another possible for the clunck.
2/ If your 'growl' noise could be described as a low whine type of noise then I would suggest the A/c compressor or its pully. I have had a whine from two Auto V6 75s much as you describe. Only happens with A/c in Auto mode and only audible at lower speeds or tickover. Noise rises a little as you increase engine speed. Dont switch the A/c on and no whine.. Switch the A/c to econ and it disappears.
Since Econ setting turns the A/c into a normal heating system and takes the compressor out of the loop I figured it must be A/ compressor or B/ pully as extra load put on it when compressor engaged.
Therefore 1 and 2 are connected.
My 2001 Saloon has had these symptoms for some 20k miles now and hasnt got any worse. Having said that I dont use the A/c great deal.