Strange noise

My 4L pushrod Ex, makes a noise like high presure air leaking through
a blown joint, this happens as the engine gets hot, say if standing in
traffic, only at tick over, goes as you rev the engine. The AC leaks a
little through the pump body, but filling once a year with a can and
gauge its Ok so don't think its that.the belt does not appear to slip.
I thought it may be the cooling fan viscous thinging but dowsing it in
WD40 makes no difference.
Any ideas

Bigusdickus wrote:
> My 4L pushrod Ex, makes a noise like high presure air leaking through
> a blown joint, this happens as the engine gets hot, say if standing in
> traffic, only at tick over, goes as you rev the engine. The AC leaks a
> little through the pump body, but filling once a year with a can and
> gauge its Ok so don't think its that.the belt does not appear to slip.
> I thought it may be the cooling fan viscous thinging but dowsing it in
> WD40 makes no difference.
> Any ideas

I had an "air noise" that I finally figured out was due to the air filter not being seated properly in the container. The oil change folks had pulled it to tell me I needed a new one. Took me a while to put the two issues together.

David