NL Petrol Strange Noises

[crh]

My NL with 120k on the clock has been making strange sounds.

On a trailing throttle (in gear slowing with foot off the accelerator) there is like a hissing sound and also when you back off to change gear. In fact, even when you rev it in neutral and back off it makes a metallic hissing/rattle sound that sounds like it is going through the exhaust.

The other is a ticking sound at idle that is loudest under the car, not a lifter type tick, but almost like a piston slap type sound or oil pump noise.

The car runs perfectly, uses no oil or water, has good oil pressure etc.

Has anyone got ideas, or have a similar problem?

Thanks.

[NJV6]

Some sort of shield vibrating? Exhaust shield maybe?

[rustygq]

hasnt got a cracked exhaust manifold?

[Dexter]

Hmmmm, I think I know the sound that you are talking about, mine has had it from new.... or as long as I can remember. Just out of interest what is your oil pressure?

[sparky!]

hasnt got a cracked exhaust manifold?

...or manifold gasket, possibly an exhaust pipe flange gasket or a holy muffler too

[crh]

I had the car at the exhaust place and he thinks it could be the cat, but in it's really early stages - it doesn't rattle when you thump it. There don't seem to be other exhaust leaks.

Dexter, are you going to say gudgeon pin noise? The oil pressure sits about mid way on the guage, I think. It of course drops off at idle. I have thought about trying a slightly heavier oil now that it is summer to see if it makes any difference. Apparently the gudgeon pin can gunk up, then you do an oil flush and the gunk is gone and you get a noise. I could have a combination of this and some other noise.

Thanks for the replies.

[Dexter]

The mettalic noise on backing off, I always attributed to a loose cat shroud or stones stuck in it, but I know the exact noise you are talking about.