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Here is some timing belt information you may find useful if you have not done this before. This page is aimed at rank newbies like me. Don't take all this as Gospel, it is just my understanding of it. I'll let you know if my engine gets wrecked.
Before starting this job, make sure you read and understand the Haynes manual, and read as many internet posts as you can. Be prepared to have the motor off the road for quite a while, and take your time. Be absolutely sure you have got it right every step of the way.
I found this job an absolute nightmare and I worried a lot over wrecking the engine, especially because most of what I read on the Internet was about guys having wrecked engines after they did their timing belt change. I took note of their woes but figured there must be millions of other guys changing their own belts without catastrophic engine failures.
Now I have done the timing belt, tensioner pulley, idler pulley, water pump, and auxilliary belt change I am more confident about doing the next one. I did this one on the drive, in the rain.

UPDATE 1 [01-03-13]
9 months has passed and the car has done 16000 miles on the new belt. The timing belt has been good (this will probably cast a curse on it now I said it). The wirring noise that appeared after the new belt was fitted is still there and has not changed (see update 3).

UPDATE 2 [15-02-14]
20 months has passed and the car has done 33000 miles on the new belt. The wirring noise that appeared after the new belt was fitted is still there and has got slightly more noticeable. I am going to have to investigate pretty soon, as I am worried the belt might fail and wreck the engine (see update 3).

UPDATE 3 [22-06-14]
24 months has passed and the car has done 43000 miles on the new belt. I finally decided to investigate the wirring noise. I removed the Auxillary Drive Belt and started the car up (why I did not try this before I really don't know). After removing the Auxillary Drive Belt, the wirring noise stopped and the engine sounded like a normal diesel again. So, it looks like things are good with the timing belt train. The wirring is coming from one of the bearings run by the Auxillary Drive Belt. The wirring noise is coming from either the Alternator Tensioner Pulley (the lower manual tensioner) 5751-29, the Alternator Tensioner Pulley (the upper automatic spring tensioner) 5751-55, the Aircon Pump bearing/pulley, the Power Steering Pump, or the Alternator.

↓ Crankshaft timing hole in the Flywheel.
The timing hole in the Flywheel is found by looking behind the starter motor.
Just to get you orientated: this view is looking over the radiator towards the right and front of the engine, to the right of the fuel filter housing. The black rubber cap marked 23 is a water pipe leading to the thermostat housing above.
The red arrow points to the starter motor.
The green arrow is where to look for the timing hole.
I used tie wraps to hold the equipment out of the way.
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The red arrow points to the starter motor.
The green arrow points to the timing hole.
The yellow arrow points to my snake led light (10 pounds from Ikea).
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↓ The Crankshaft sprocket.
This is locked in position when the flywheel timing hole is pinned.
Later on I thoroughly cleaned the whole timing belt enclosure before letting the new belt anywhere near it.
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↓ Camshaft sprocket.
The Camshaft sprocket on the left has to be pinned.
Once the Flywheel timing hole is pinned, the timing hole in the hub of the Camshaft sprocket should then be around 7 or 8 oclock.
Here you can see an 8mm bolt has been inserted in the timing hole, around the 7 oclock position, to pin the hub.
The Camshaft sprocket hub is the round piece in the middle, with the arc of drillings on it. The hub is keyed to the Camshaft and secured by the single bolt in the centre . The hub bolt is not touched at all in this operation.
It is the Camshaft sprocket hub that is pinned in this operation.
The Camshaft sprocket is fixed to it's hub by the 3 bolts. When the 3 bolts are loosened the Camshaft sprocket can turn freely on it's hub.
The Camshaft sprocket is turned ever so slightly in order to take up some of the slack on the Timing Belt. It should not be moved more than one sprocket tooth.
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↓ The injection pump sprocket on the right does not need to be pinned.
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↓ Crankshaft Pulley bolt.
You must make sure that the Flywheel and Camshaft timing pins are removed before undoing or tightening the Crankshaft Pulley bolt.
You must not put a pin in the Flywheel (or Camshaft) and then use that 'lock' to remove or install the Crankshaft pulley bolt. A few lads on the internet forums mention they have used this method and give the impression that it is a correct method. It just does not seem right to me.
To remove the Crankshaft Pulley I used a Clarke CEW1000 Electric Impact Wrench from Machine Mart. Rather than splashing out on a load of air equipment I decided to give this cheap option a try. I got mine on a Vat free weekend. This wrench claims 450 Nm of max torque and a 1.01 kw max Power Output (whatever that means). I think you need to ensure your power cable has an adequate conducter size so it can deliver the maximum current.
To remove the Crankshaft Pulley I had the car on stands. I dragged my son away from his computer and got him to engage 5th gear and put his foot on the brakes. Two or three bursts with the impact wrench and the Crankshaft Pulley bolt was loose. Happy days.
Tightening it back up was not so easy. To tighten up the Crankshaft Pulley bolt I had 5th gear engaged. I torqued the bolt up to 40Nm using a torque wrench and then tried to do the stage 2 torque of 55 degrees. I could not do this as I could not prevent the engine from turning. I think maybe the clutch was slipping? I ended up giving it a few burst with the impact wrench and hoped it was tight enough. I don't think it is properly tightened. I marked the bolt with tippex before going at it with the impact wrench and it only turned 30 degrees or so. Later on before installing the wheel arch cover I gave the bolt a few more bursts with the impact wrench, but it did not appear to turn.

↓ Timing Belt.
If your existing timing belt is intact then do make sure you mark it with Tippex or something, before you remove it or release the tension on it.
Pin the two timing holes and then immediately mark the belt and the sprockets in various places. Put two or three marks at each sprocket. Once the old belt is removed you can carefully transfer the marks onto the new belt. When you are fitting the new belt you can line it up to the corresponding marks on the sprockets. This will tell you if you are installing the new belt correctly. The new belt should go into the same teeth as the old belt.

So, how tight should the belt be. I honestly don't know. The Haynes manual says to tighten it 'until it just possible to twist the belt slightly midway between the Camshaft and Injection Pump sprockets'. This seems very tight when I compare it with what others say. Others on the internet say they use the twist method, if you can just turn it 90 degrees between thumb and finger then that is ok. But then others quote 45 degrees for the twist method. What to do, what to do. This is where you need an experienced teacher to steer you in the right direction.
My belt had done 90000 miles. Midway between the Camshaft sprocket and the Injection Pump sprocket I pushed it down vertically as far as it would go, then lifted it up vertically as far as it would go and the distance between the down and up extremities was 25mm. I could only twist the belt to about a quarter of a full turn, about 90 degrees. Also, when I tugged the belt upwards with moderate to firm pressure at the midway point, only two teeth lifted off the Camshaft sprocket. The very first tooth that engaged the Camshaft sprocket (the one nearest my hand as I was tugging) was nearly lifted out of its trough, i.e. the bottom part of the tooth almost reached the crest. The bottom part of the second tooth that engaged the Camshaft sprocket just came off the bottom of the trough as I tugged the belt upwards. I figured the belt could not have stretched too much in service, else I would have had problems. So, when I installed the new belt I tightened it to about 20mm play in total (around 10mm when pushed down), just so it was mildly tighter than the belt being replaced. Time will tell if I got it right. I will worry about this for a long while, praying that the engine does not become suddenly wrecked.

At first I tightened the belt 'very' tight and I could only just twist it out of the horizontal, as per the Haynes instruction. I cranked the engine over by hand 8 times to check the timing. The timing was always good during this operation and never a problem because I followed the Haynes instructions precisely. However, during this episode, the belt started to walk off the sprockets. I did not have the Crankshaft Pulley fitted so maybe this was part of the reason that it was walking off. Stress! I slackened the belt tension to about 25mm play. Now, with the belt horizontal, when I twisted and lifted one edge up (with a moderate amount of pressure) I could just about twist the belt so that the edge almost came to the vertical with a fair amount of pressure (i.e. I could just twist the belt just under 90 degrees, a quarter of a full turn). I cranked the engine another 8 times, this time with the Cranskshaft Pulley on the bolt. The belt remained on the sprockets. Somebody had mentioned that the Pulley helps keep the belt on. I would have thought the side of the belt would wear if in constant edge contact with the Crankshaft Pulley, but what do I know. I cranked the engine over lots and was satisfied the belt did not want to walk off the sprockets. The belt did not follow the same track as the old belt though. The new belt wanted to track on the Camshaft sprocket about 1mm further away from the engine block than the old belt did.

↓ Testing the job.
After virtually putting it all back together again I waited around for about an hour before I plucked up the courage to turn the engine over for the first time. I still had it on stands with the wheels off, so the front was raised. I turned the key, expecting immediate failure. Instead, the engine fired first time as normal and started to idle as normal. The engine was making an unfamiliar wirring noise though, so I turned it off. As I turned the key to off, the engine revs went 'up' before the engine came to rest. Cripes, it had never ever done that before! I worried some more. I tried the engine a few more times (for a few seconds at a time) each time fearing the worst. Nothing catastrophic happened, but the engine always revved up before coming to rest, and there was that new noise. I then let the engine idle for a minute. The belt was staying on the sprockets.
Later when the car was off the stands the revving up did not occur again, so it must have been down to the angle it was at while on the stands and this was maybe affecting one of the engine management controls?

I worried about the new wirring noise so much so that I removed the top timing cover (long job) to inspect the belt and see if anything looked amiss. The belt was still in the same place on the Camshaft sprocket and looked unmarked. I may inspect it again after a few hundred miles and see if has become marked. Mind you, inspecting the timing belt on this HDi is easier said than done as it is a ball ache just removing the top timing belt covers. I would have designed the covers to make things a lot easier for everyone. It would have been so easy for them to design the cover so that is can be dismantled without disturbing the engine mounting bracket or disturbing the water pump.

After putting everything back together and I eventually had it sitting on its wheels again. I started the engine and let it idle. I did not rev it above 1000 rpm. I figured there would be less damage if it failed while the revs were low. I let the engine warm up and did the coolant.
After about 30 minutes of idling, still no catastrophe. I then drove it up the road in first gear, at around 1100 rpm.
I drove it up and down the road, each time going a bit faster, but keeping the revs low and listening out for anything strange. The new noise worried me.
Anyway, this was 3pm, and the Mot was due at 4pm. So I bit the bullet and drove it to the Mot Station, and kept below 40mph and did not rev it up too much (I would let the Mot guy do that!). It was still making an unfamiliar noise though. I asked the testing guy at the dealership if the engine sounded bad to him. He said it sounded alright seeing as it had done 152,000 miles. These guys come across thousands of cars and he would have said if there was anything grossly untowards about it. So, I am putting up with the new noise. As one of my mates once said, each car has it's own character.
It sailed through the Mot without fault. Last year it cost me 14 pounds as it failed on a lower arm ball joint.
I am feeling much better now I am this side of the job.

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