Assuming your talking the 105bhp 8 valve engine it's doable without locking - due to the crank oil seal going I've had mine on and off three times over the last year. With care the only locking up is on the flywheel ring gear and that's only debatable to be necessary if your changing the water pump (recommended) or if you need to remove the bottom cam belt pulley, again only necessary if you need to address a leaking crank seal. Of course, if it's not leaking leave well alone.
Back to the cam belt removal, first job jack up the off side front and secure with axle stand/s under the suspension arm bush/fixing bolt bracket area nearest to the centre of the car to give you plenty of working area when you do the belts. Remove the off side front wheel. With all well secured, go on to remove the auxiliary belt. 15mm spanner with a large spanner (27mm or similar) for extra levering. Take a photo before removing so that you've got a visual reference when you put the auxiliary belt back on. Interlock the 15mm spanner up through the larger 27mm ring spanner and fit the 15mm onto the auxiliary belt tensioner. With the DIY extended spanner via the 27mm spanner if you get my drift, push up on the tensioner to release and the belt will easily pull off the tensioner pulley. From there you will be able to slip the auxiliary belt off the alternator, air con condenser (if applicable) crank shaft larger pulley etc.
Now onto the cam belt, for me this is the make your mind up time if your going to change the waterpump. If yes, find the small inspection plate under the bottom of the bell housing. IIRC 8mm bolts, remove the plate. Eventual locking of the engine is only necessary if you opt to loosen the cam shaft pulley to give a bit more room to fit the water pump. This is my take only and better advice may follow, but when I done my water pump it could have easily be damage due to the soft alley material is cast from by forcing it under the cam shaft pulley.
With the front off side wheel off and a trolley jack under the engine for support (believing it to be the strongest area and to give optimum working area, I put a block of wood under the bell housing area where the exhaust bolts on) and supported with the trolley jack. Remove the top off side engine mount. Also loosen off the coolant expansion tank and power steering reservoir tank. No need to remove any of the pipe work.
Put the car in gear and remove the 4 torx bolts from the bottom crank shaft auxiliary belt pulley. I found it easier with a 1/2" socket and thump the handle with my hand to initially shock release the 4 torx bolts before fully undoing the bolts. From there remove the pulley to reveal the cam belt bottom pulley.
Next is to remove the cam belt casing. You make life alot easier for yourself by gentle jacking the engine up to remove the top cam belt casing and then down There is a auxiliary belt idler pulley that can be remove to give a bit more room for fitting the new cam belt but be careful if you use a racket spanner because you won't be able to remove the racket spanner once fully undone.
With the car in neutral, via the bottom crank shaft bolt (19mm) turn the engine by hand so that the timing marks align. Marks being on bottom crank shaft pulley and to cam shaft pulley (triangle shape moulded in plastic rocker cover). If necessary, with a marker pen or tipex, mark the pulleys. Once all aligned and your happy and if you elect to change the water pump, lock the flywheel ring gear. A special tool can be purchased but I made one up using stiff cardboard for a template then got the angle grinder on a piece of box section metal to make a locking tool. Need to ensure it covers at least three teeth on the flywheel ring gear. Since found out that using 3 centre punches pushed in side by side will do the job. With the ring gear locked, loosen the top cam shaft cam belt cog. ONLY slightly loosen at this stage. If the timing belt marks still all align correctly you can leave the locking tool in the ring gear. If not, then remove the locking tool and realign the timing marks.
Dare say book will tell you to lock the bottom pulley, but I've found, with care, it's not necessary. From here you can release the cam belt tensioner then remove the cam belt.
Again, highly recommended, it's best to fit a new tensioner kit. If you don't go for this option, at least take the cam belt tensioner and idler pulley of and spin by hand and listen for a rumble in the bearings. If there is, then definately replace. Your choice to refit the old tensioner and pulley, but for the money involved and if either let go after the new belt as been fitted, it will cost a lot more money to sort out a smashed engine. This is where a new water pump comes into the equation as well. Going onto the water pump replacement, with the belt removed, slightly loosen off the cam shaft top pulley. No need to remove completely but you can do if you wish to give alot more extra working area fitting the pump. With the new pump fitted, refit the cam socket making sure the timing marks still align. I wouldn't tighten fully at this stage so as not to risk the timing alignment. Wait till the belt is fitted and you can relock the engine.
Cam belt tensioner is a bit tricky. On a bench, lever up then tensioner to its maximum and fit a bolt in to secure it. This can be tricky but well worth doing. IIRC I used a 8mm 25mm length bolt because it fits up into the tensioner and wedges against the plate. Very important, make sure the bolt head doesn't pretrude out of the tensioner plate. You need the plate to fit flat against the engine when fitting hence why you don't want the bolt head pretruding. When you've got the tensioner in full view you will understand and see my point (a bit difficult to explain in words).
Fit the new belt by going round the bottom crank shaft pulley up the right hand side over the cam socket then the diesel pump socket leaving the slack area for the tensioner. If possible get somebody to help hold the belt on the bottom crank shaft pulley whilst you do the top pulleys, just to ensure it doesn't slip. Now offer the tensioner on. There's an obvious slot in the tensioner plate that fits over a stud. Gentle slip the tensioner up to the belt and secure. Once secured, with a long nosed pair of pliers, remove the 8mm bolt that you wedged in the tensioner. This will release the tensioner spring to the correct tension. Can be a bit tricky, but if you get it right, it works well.
Now relock the engine and tighten the cam socket correctly ONLY WITH THE NEW BELT FITTED AND TENSIONED. Check the tensioner bolt for being tightened correctly. Via the bottom crank shaft bolt, with a socket, hand turn the engine to satisfy yourself that all is turning smoothly and the timing is correct.
Being nagged by the wife now for being on the laptop to long so refit all the ancilliaries in reverse to removal and all should be well.
Forget to mention, it's not necessary to lock the fuel pump because it's common rail so timing is not an issue.
Hope this helds and good luck.
P.S. new timing belt kit and water pump approx. £100-£120. Worth it in my book
