My Landrover Disco 2 2000 makes a scratching noise every 20-30 seconds when idling.

Where are the CarGurus? The LarsCats, DavidH25 etc

Heh, we're in need of some downtime too from time to time. I can tell you it's not the fuel pump (which is an in-tank model on Disco II's) or pressure regulator (which is on the fuel rail on top of the engine). Sounds more like the ACE-pump or the air pump for the SLS to me but it's hard for me to be sure without a picture, that Delphi part number means less than nothing to me.

Additional you may want to have a gander at thisvery useful page: http://landrover.workshop-manuals.com/discovery-ii/index.php

Many thanks Lars! Your responses help many enthuasists out there. I will definitely post a picture for the ailing part. I appreciate the above link as well.

From the information I have gathered so far from the link you have provided, the scratching noise comes from the ACE system component (as you correctly mentioned in your first thread) that has the pressure transducer, Valve block, Directional Control Valve 2 off and Pressure control valve. It is localised among these components on the right hand side of the chassis. Just wondering how to resolve it. Anyhow, I will still post a pic to you the CarGurus. "when a problem is correctly identified, to is half way resolved"

In that case you might want to flush the ACE-system and put new fluid and filter in. Often the pump gets noisy when the fluid starts to lose viscosity due to fluid overheating.

Any tips on the procedure to follow when undertaking the ACE system flushing? Any dos and donts... Really appreciate your support!

1. Change the filter. You will want a pan to catch drips. The ACE filter is in the machined block on the passengers side underneath the car - about 1/2 way between front and rear. Use a 10mm hex to remove this cap. Next take a 6mm bolt and thread it in the hole on the bottom of the filter to give purchase to pull it out. Installation is reverse of removal, ensure to apply some ACE fluid onto the o-rings before installation. (This procedure should also be in the manual under 60.60.21) 2. Change the fluid. You can choose to suck out all the fluid with a syringe, fill it back up, start engine to circulate, stop engine and repeat until clear. But this will cost you a lot of fluid if the fluid is very dirty. For the alternative procedure you will need someone to give you a hand. First drain all fluid out with a syringe. Next remove the return hose (the smaller one) and plug the nipple at the reservoir. Push some clear rubber hose with an outer diameter roughly as big as the inner disameter of the return hose into the return hose and secure it with the clamp around it and put the other end of the clear hose into a waste container. The next will require a bit of finesse or the removal of your sparkplugs because the ACE pump displaces a lot of fluid. So either have your helper just switch the key on and off, just to rotate the engine without starting it or just pull the plugs and crank it for short bursts. This will quickly pump out all the ACE fluid, so top up the reservoir regularly and repeat, make sure you do not let the reservoir run dry! When you start seeing your nice new clear fluid run out of the hose remove the clear hose from the return hose and the plug from the nipple. You will need to be quick about stopping the fluid draining from the nipple until you can get the return hose securely on. Finally wipe up any spillage and top up the reservoir to the Max line. Let the engine run at idle for a bit, then turn it off. Check the fluid level and, if necessary top up or suck some out if overfilled.

I forgot to add 3. Go to your fridge, grab a beer and celebrate the marvel of technology you've just spent the past few hours swearing and cursing at with scraped knuckles and oil drenched clothes :)

Now this is what we call "hand-holding" or unlimited vehicle maintenance guidance. The information provided above is invaluable and will be applied as guided. I just hope, I wont be tempted to start from Step 3 to Step 1. Many thanks Lars - CarGurus. This will definitely help many Disco 2 enthuasiasts out there. The outcome shall be posted right here. Keep it up and my regards!

You're welcome, some things are good to learn by doing, with others it's better to learn from other peoples messes ;-)