Astra cam belt

[Rob 1049]

Do Vauxhall Astra's have a fail safe when the cam belt snaps ?

[Ewood27]

Sorry to be the bearer of bad news, but when this happened to a friend's Astra it led to a BIG bill to pretty well rebuild the engine. If it hasn't snapped yet and it's due, get it done. It'll be a lot cheaper.

[thecooler]

If the belt breaks the pistons can hit the valves and bend them. It happened to me recently and the local garages were quoting anything from �500 to �1100 for repairing it. Mine is a Daewoo Nubira 2l, which uses a Vauxhall engine. As I don't have that sort of money I decided to do it myself. Took about four days in the street outside my house and cost me sixty quid including a new belt, two new valves and a head gasket. Has yours broken?

[New Forester]

I can't see how you could have a fail-safe for this. The engine is whizzing round, pistons are flying up and down, valves are nipping in and out -- it's all got to be perfectly coordinated, because the open valves overlap with where the piston is when fully compressed. When the belt goes the engine carries on going, but the cam stops very soon. If you are lucky it stops with all the valves closed or nearly so, and the pistons don't hit them. More likely it doesn't. A fail-safe would have to lock the cam in a safe position within less than a turn -- but leave it free under normal conditions. It happened to me in a diesel Peugeot --it needed a new cylinder head, though luckily the pistons were OK. Quite a new cam-belt too. You could have a side-valve engine -- that would be OK.

[allan.g0ias]

No.... only a big repair bill..unless your lucky, X amount of Revs,,, pistons going up and down like bees wings,,, belt snaps, pistons STILL going up and down,,, valves not opening and closing... just in the position they were when belt broke... if lucky...no bills, only for new belt, if not ...get ready, Answer is to swap belt if in doubt... but STILL no guarantee it wont happen.

[sddsddean]

I think what Rob means by a fail safe NF, is like what I had in my old Vauxhall Victor. I think this was the first car in the UK to have a cam belt instead of a chain (though I stand to be corrected). As the makers were unsure how the belt would perform, they made sure there was clearance between the pistons and valves. The result being, when the teeth on the belt stripped, all I had to do was replace the belt, re time the engine and drive off. I don't know why manufacturers continue making them non fail safe. Had the same thing happen with a Rover 800 series (only 5000 miles after it was routinely replaced) and it bent 8 out of 16 valves. If it wasn't for the valves, it is a dead easy replacement job. Obviously they want you to have to spend loads of money at the garage.

[New Forester]

I see what you mean, sddsddean. However, I think it'd be very hard with modern high-compression petrol engines, and surely impossible with diesels, where the compression ratio might be 20:1. The minimum gap between the piston and the head is so very small, even with holes sculpted in the piston face. I suppose that it might be easier on multi-valve engines, as the valves can presumably be smaller. I had a cam-belt skip a tooth on that same diesel Peugeot (because something got jammed in it). Even one tooth off was enough for the valves to touch the pistons (just) at high revs -- and it didn't have much power either. Amazingly it didn't bend any valves.