Hi,

Hard one to explain but here goes,

when the car is idling is has a 'tapping' sound from under the engine that kind of ramps up & then down, best visual text representation i can give you is,

..........tk....tk......tk..tk..tk.tk.tk.tktktktktk..tk..tk.......tk.............

Over the space of about 5 seconds, then repeats.

Any ideas?

Hmmm. Sounds like an alternator pulley to me.

I think they use a clutched pulley to stop the belt being shredded on overrun.

They can often tick or make a squeely/scratchy noise.

phil

Use a stethoscope for mechanics to better locate the sound.

If you don't have one, you can use a long screwdriver. Put the tip on different places and your ear on the handle.

OK, had it in with mechanics, not 100% sure but they reckoned the water pump making this noise, they used the screwdriver as you said without me prompting them, this could be right as the car is running a little hot, temp guage is just over half way when on motorway, looks to be holding at about 100'.

I checked with engine cold by taking the cap of the coolant reservoir to see if there was anny flow & it didnt appear to be flowing but when the engine heats up the resevoir is hot & the fan kicks in on the rad when needed.

Do you think it might be water pump?

One other thing to note which may help diagnose, the very bottom/back fly wheel under the timing belt etc was replaced with one from a caddy some time back, the wheel is wider than the rest but the belt runs fine on it, is this the wheel that drives the water pump, could it be a bad job done when it was replaced?

The noise appears to be gtting louder but dissapears when you accelerate, it is only audible when the car is idling.

Any ideas?

When the engine is cold, the thermostat is closed, so there is no flow any place other than the block and head internal waterways.

The lower pulley you are talking about is the crankcase pulley.

The water pump body is common with engine mount.

Usually a bad water pump starts to leak from a special hole in it when they're worn out.

From your description is more likely that something is out of balance and resonates louder at idle.

It can be one of the pulleys, especially the crankcase one, that needs to be original and balanced.

As for the slightly overheat engine, a new thermostat and a thorough flush of cooling system make wonders.