Greenmamba

Me, or the OP?

If it's the tensioner pulley, not the idler pulley be careful - there is a nut behind the bolt (which holds the pulley itself onto the tensioner) which can get lost down a crevice and you will battle to get it out. Has the tensioner itself failed or are you replacing just the pulley?

Nice one!

Full change of transmission fluid.

First of all, auto box - check transmission fluid. Level and colour/smell. I'm assuming it's auto. Check with engine running in park. If fluid is too high or too low, sort it first. Check colour - should be pink. If not, change it, few drain and fills may help. 4 speed or 5 speed?

Welcome

Changed the v belt, tensioner pulley and idler pulley.

Subarus are known to prefer OEM thermostats. They open at similar temps but have a larger capsule than "compatible" others. If it's not OEM, try a new OEM. Not much cost, not much to lose.

Is it a OEM thermostat? Have you considered a leak down test?

If the block test changed colour from blue to yellow, that's a sure sign you have combustion gas getting into the coolant and the only way that'll happen that I know of is HG failure. It's probably early stage but still...There is probably blow through at one cylinder. Pressure test wouldn't necessarily prove anything in this regard - the problem occurs when the engine is hot and expansion happens. Good luck anyway.

I believe it'll make a significant difference. In effect, wouldn't the front and back wheels be trying to rotate at differing speeds?

Looks like a gizwag flasher unit controller for alternate headlamp flashing like cops use.

Those springs are notorious for rusting out. Mine has done just that. Just got used to manually returning the handle to the "closed" position.

What you are seeing is the accessory belt, droves the aircon, power steering pump, and alternator. Also called v belt. Can need changing, if you do it's recommended to change the idler pulley and the tensioner pulley as those bearings can and do, fail. Easy to do.

Def chain. Only replace if noisy/failing. Known to go easy 300k miles provided tensioners etc don't let go.

Howdy and welcome. Good choice!

Put my summer tyres on.

Is that a diesel?

'Cause we had one (green mamba snake) in our kitchen ages ago (long story) and 'cause I've owned 3 green Subies in my time.

There is a silver 3.0Rn OB on eBay right now, the seller is asking £2600. If anyone is considering http://www.ebay.co.uk/itm/162406502385?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT I urge you to contact me (pm) before buying; I know something which may be useful about it.

Airbag warning light could be clock spring fault. Does the hooter work?

How's the battery in the remote? Make sure when you connect the car battery that the key is not in the ignition.

Regarding the tailgate water. No obvious damage around the window beading? Have you tried taking off the inner liner and looked for obvious signs of water ingress? If they have sunroofs, drains may be clogged, water then gets into the tailgate via the flex rubber boots near the hinges (carry wiring into the tailgate). Check light clusters for small cracks.

The scarcity, the space, the power. Finally, when it snows.

Check all hose clamps on fuel lines in the engine bay are tight - cold tends to cause contraction and sometimes leakage.