Knocking sound

[strange_rover1]

Gday all,
I have a strange problem with my Mother in laws P38, every now and then it gets a loud knocking noise which sounds like a little metal hammer is knocking on the windscreen. It seems to come from under the dash right up near the very bottom of the windscreen on the drivers side. It does about 5 loud taps then stops and it wont be heard again for a few days.
Any ideas anyone?
Shano

[Scouse]

The ABS pump is just in front of the firewall in the engine bay. Could it be that making a noise sometimes? It should just buzz occasionally but I guess it could get noisy if it's on it's last legs.

I wonder if a blend motor could make a noise too. I can't say I've heard one make a noise like that though.

[strange_rover1]

Thanks Scott,
Do you know where abouts the blend motor is situated?
Shano

[Scouse]

There's 3 blend motors all up & they are buried in the dash. As I said though, I haven't heard of one make a loud noise like that. There's not too much else that can make a noise from under the dash as far as I know.

It's not a relay buzz type noise, is it?

It may be one of those impossible to trace noises until it does it often enough to find the source.

[strange_rover1]

Nah the only way I can explain it is if you hit the windscreen lightly with a hammer, that is the sound and I have only heard it once!! It is really bizzarre!!
Shano

[Rusty Rangie]

I every now and again get a cluncking/knocking noise from the same area.

After a long time trying to figure it out, I have determined that it was the airconditioning pipes. For some reason, they some times make this noise, I can feel the pressure spike accompaning the noise if I hold my hand on the pipes running along the back of the engine bay. It took me ages to figure this out because it really happens.

Hope this helps

Cheers Rusty

[mike 90 RR]

Any ideas anyone?


If it's more like a crackling sound .... could be just the cold air reacting to a hot dash .... I get this noise when I turn on my A/C on the RRC

Metal & plastic contracting when cooled

Mike