Good advice from RUM above. From the year and that you're talking about a cam belt, I assume your engine is part of the EA211 engine family? I have the 3 cylinder variant CHZB version of this engine and was "troubled", just as you are, with the lack of definitive info about these points. The drive belt for the water pump on the other end of the cylinder head doesn't have any recommended change interval either! And, I'm a sceptic and natural born worrier when it comes to stuff like this.
RUM and I - and other contributors - have had some conversations about this and I've talked to a number of mechanic friends (I'm a retired spanner wielder) and have reached some conclusions which have made me much happier. The
problem for me is that I'm a chap who started out in the days of the likes of Austin Cambridges, Minis (the old ones) Hillman Avengers, Ford Cortinas (Mk1 etc). Then, one day, a Fiat 128 suddenly appeared needing a new cam belt - A what? A cam belt son, here's the bits, just get on with it! and so soon the others followed suit, the Ford Pinto engine in the Sierra, "O" series Leyland in the Princess, Marina, etc and many others - Oh if only modern belts were as easy to do as those old soldiers - Most typically needing changed at around 4 to 5 years old or around 60,000 miles. Ignore that and either the belt would fail or, more likely, the bearings in any idlers, tensioners or water pump in that drivetrain would collapse and the timing would jump and, Good bye engine.
So, bearing in mind that these thoughts are in the back of my mind, I wasn't very impressed by statements such as "but these days the belts are much more reliable and long lived" or, "we don't often do one of those". Well I agree that the belts have been improved greatly and are pretty bullet proof these days but, thinking back on the one's I've done it's very often the pregreased sealed for life bearings in the idler, tensioner or, more often, water pump - if part of the timing belt drive train - which have failed and then caused a
problem with the belt and these components, which should always be replaced if part of this drive train when doing a belt, don't seem to have improved all that much. So, with all this in mind, and that I firmly believe prevention is much better than cure - I like RUM's concept of being "smart" - I elected to change the cam belt at 6 years old (actually about 6.5 years in the event) I still think of this car as my "new car" so chickened out of doing it myself and got AVW to do it for me but I think I might try myself next time if I still have the car - and am still driving - at that time. The old belt would undoubtedly have gone on for a while yet but there were slight signs of fraying of the smooth belt backing in one area. Interestingly perhaps? our local main dealer and two of the indies I've asked have recommended a five year change interval on the cam belt so maybe now they've been around for a while they are discovering it needs it?
The water pump toothed belt - looks like a little mini cam belt - worried me too but in the end I was talked out of having it changed because they told me they only touch them if doing a pump or rectifying a leak etc, not as a service item. I've never been really happy I agreed to this and have been doing a lot of looking into it. So, nearly a year on now from the cam belt change, this is my present take on it: To change this belt the water pump will have to be removed from the cylinder head. Looks pretty daunting when you open the bonnet and see the spaghetti of water pipes. In fact it's not that difficult for anyone who has done "serious" work on cars and I will definitely tackle this myself when it's needed. Ah, I hear you all saying, but when is that? The answer is I don't know but there is a little black plastic cover over the camshaft drive wheel which I think can be easily removed - haven't tried yet and it may involve unbolting a breather, which may mean replacing it's "O" ring seal, but it looks very doable. Having removed the cover you will be able to inspect the belt and see if there are any leaks from the water pump bearing. If all Ok then I'll just refit the cover and carry on. If not I'll strip the pump and thermostat as an assembly (it contains 2 thermostats) and replace the entire assembly. I've made this decision because the thermostat housings are plastic - so may be subject to warping, especially if slackened - and there are multiple seals between these housings and the pump itself and the head. Then there's always the thought that old thermostats may malfunction and I don't want to be having to strip it all again, and maybe buy new seals, just to replace a thermostat later on. I'm hoping that removing that belt top cover proves easy to do, If so I'm going to inspect the belt/pump every year just before we go on our annual road trip to the "deep south" every spring and then again just as winter starts to set in and before the cold weather comes which makes working on my drive difficult for these old bones. I think 2 inspections a year should find any problems before they become catastrophic. For what it's worth I think the water pump bearing is probably the weakest link here and more likely to fail than the belt itself. So you can listen for "bearing noises" and inspect for coolant leaks - which seem to accumulate on the top of the transmission so should be easy enough to see on your weekly checks? Unlike most other water pump installations I can think of, the belt is very lightly tensioned so side loading on the bearing is going to be pretty minimal which bodes well for longevity of the bearing.
Spark plugs? I got the car serviced by the main dealer while it was under warranty (and I'm glad I did as she had the early turbo on her and suffered the seized wastegate
problem needing a new turbo to be fitted - the uprated one has been fine) Then when I started servicing her myself at her 4th year I did all the usual stuff like oil and oil filter, air and cabin filter, I like to keep cabin filters in all our cars "fresh" partly to combat smells but more importantly to ensure a good flow of air to the cabin blower resistor thus, hopefully, stopping it burning out prematurely - isn't the cabin filter a beaut to do? but heard of horror stories of the coils disintegrating when you tried to pull them so I left the plugs alone. I did a lot of asking around and reading about it and discovered that what happens is that sometimes, especially if you don't pull straight up on the coil, the rubber boot detaches and stays in the plug hole which is then very difficult to get out without damaging it. I didn't get much further with doing the plugs but decided to get AVW to change them for me when they did the cam belt (mentioned above) So they were roughly 6.5 years old with just under 25,000 miles when changed and running perfectly well. I'm sure they would have gone on for a lot longer. I now know there is a special tool to
help with coil extraction. here's an example:
https://www.ebay.co.uk/itm/11562217...3l0J+PwvjL9hJoGDkEHA1ukVQQ==|tkp:BFBMht3T0p9h It helps you pull up vertically on the coil and I'll be buying one next time they need done. If the rubber does come off and stay in the hole I'm lucky enough to have an air compressor so can use compressed air to simple blow it out. The prospect of doing the plugs no longer worries me. and I'll just do them every 6 years at the same time as the cambelt from now on - or until I sell the car or stop driving.
This post is getting too big to be entered so I'll stop here and do another continuation in a minute