Re: Astra cambelt woe's

I don't undertand this sentence. Surely fitting a new belt in exactly the same place as the old will result in the timing becoming slightly further 'off' due to stretch in the new belt?

Exactly as in tooth for tooth, as in the same amount of cambelt teeth between set points on the pulleys from the old belt to new belt. Then when the tension on the new belt is set, it will be exactly as the old belt was when it was new as in un-stretched.

After advice from previous threads, I attempted to check out the settings on a previously hurriedly replaced (using Tipex marks) cambelt on my Astra 1.7 diesel, this time using the correct DTI tool. Not being too bright on the mathematics front I found that on setting up the tool to zero at 90 degrees before TDC, then sliding it across the cam 10 mm and then winding it on to TDC, instead of going to somewhere around 0.55mm I was baffled by the fact that it made a complete revolution and a half, however after a while it eventually sunk in (what I presume to be the correct procedure?) that the actual measurements is between it 'zeroing again' and where the needle actually stops, in which case it was 100 percent spot on at 0.55 mm. This time I was was prepared and had a replacement belt guide roller and water pump, checking the roller (which I nearly didn't replace due to its inaccessibility) I found that the plastic surface had bubbled and on spinning it was noisy and had very slight lateral movement. On replacing everything and rechecking with the DTI I found that the reading was then 0.6 mm at TDC, presumably something to do with replacing the guide roller. The book says that that tolerance should be within 0.03 mm which would have meant removing the bolt on the camshaft pulley and adjusting the camshaft with yet another special spanner tool arrangement (which I don't possess) and renewing the bolt. As twilight was upon me, I put everything back together and took it for a good hard spin, I'm now wondering that as everything has been renewed and the car is running OK, should I go through the setup procedure for the sake of a 0.02 mm out of spec discrepancy on the DTI?

Hi Ivan, I have the same car as you 1.7 Non turbo. I have had to set the timing on my Astra due to removing the head (to repair the damage done by the garrage who set the timing up wrong)

I think personally and it's only my personal view, that you should be ok. Especially as you have not removed the cam shaft pully. Replacing the tensioner will only have a marginal effect on the timing as it is on the slack side. The only way the tensioner can effect the timing is by slightly streching the belt due to the spring being new. Given the extreemly small tollerance specified for this engine I'm not sure that you can set it as accuratly as they recommend. When I set mine up I checked it several times just to make sure and I got it slightly plus and minus (cant remember how much now) each time. As I had found it + & - I decided that it must be about as close as posible and let it go at that. This was about 500 miles ago and she is still running OK. When you look at the spec .03mm it works out to be .001" which is the what most Impereal DTI's read in, so I suspect that when the engineers at Vauxhall formulated the spec they decided on 0.001" and then found that they should really quote it in metric hence 0.03mm

Hope the above is of some use to you. Please let me know how you get on. Jonathan-Dabbs-2004

Thanks Jonathan, the version I have is slightly earlier, and uses the water pump as the tensioner, the guide roller is a plastic pulley on the outside of bearing . Originally the fuel pump was about one notch before the alignment mark on the block and try as we might even two of us couldn't get it to line up, the reason being that there appears to be a bloody great spring in it and as soon as the notches were aligned it shot forward about half a revolution, with apparently no kind of facility for locking it in position. Likewise the flywheel, trying to get the t.d.c marks to remain lined up appeared to be an impossibility, as it seemed to have a mind of its own after removing the spanner from the crankshaft pulley it crept off in another direction, again with apparently no facility for locking it and after about 15 minutes - with darkness descending - of trying to get the belt to fit (it's all in a very tight space behind the bulkhead) we gave up and left it in the same position as the old one, and no doubt for exactly the same reason that someone else previously had!. It all looks so easy in the Haynes manual where they have a nice clean engine on a bench with all of the gear exposed, and casually informs one to "align the timing marks".