What happens when a cam belt breaks?

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Laura4363 | 17:57 Thu 17th Feb 2005 | Motoring
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I know it probably seems a daft question but I'm only a girl! And I have a feeling that yet again I've been diddled by a dodgy garage. What I would like to know is, how would i know if it was the cam belt that had broken, and what would the garage need to do to fix it. Also how much should it cost to fix on an R reg Peugeot 106?


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You would see that the cam belt has physically broken.  The engine would start and the engine would turn over without any compression at all.

If it is broken then it usually major work.  On some engines they may try fitting just a belt and see if it starts; if it was a car I was unfamiliar with that's what I'd do first.  If it does start and has no compression then it's bent the valves.  Major work!

Remove the engine head and inspect the valves to see which are bent.  In worst case scenario all 8 (or 16 if it's a 16 valve engine) valves would be bent.  Usually it's just 2 - 4 valves bent.  The valve guides may also be damaged and check for movement on the pistons.  So, replacement valves need to be ground in, then head refitted with new gaskets, usually new coolant etc.  Quite a longish and expensive job!

Cost?  Wouldn't like to say... anything between �500 - �1000 depending on damage.

There are little upside-down mushroom shaped pieces of metal called valves at the top of every engine.

They open and close in time with the pistons going up and down to let fuel in and gas out.

The cam belt links these valves to the pistons - if it breaks the pistons can hit the valves and do a lot of damage and that means opening up the engine.

Whenever you buy a secondhand car you should always find out when the cam belt was last changed and ask to see the receipt for the work. If you don't have that assume that the cam belt needs changing and get it done as soon as you've bought it. If you know when it was done make sure you know when it needs doing again.

It's not that expensive to get a cam belt changed - it's very expensive to get the damage repaired.

Recommended intervals vary but 70 thousand miles is  not untypical.

As KebabMeister says the engine will most likely turn over but not start. The garage will proably have removed the valve cover and turned over the engine if the valves don't move they'll know the belt has gone.

I presume the car just cut out on you with little or no warning.

Thing is the garage will know that they've got a likely captive job if the car is a non-starter so will be conservative on their quote. If it's a main Peugeot dealer it's likely to be very very conservative.

You could try calling a few garages and ask what they'd quote to fix a failed cam belt but don't be surprised if they don't wan't to commit themselves because they won't know how bad it is until they open the engine.

Hope this helps

Question Author
Thanks both!  Still not sure if I've been diddled though... The car cut out at the end of the drive so had only gone about 10 yards.  I called the garage I bought it from (who told me at the time it was a great little runner that had been fully serviced etc etc....) and they took it away and told me the cam belt had gone and it was a big job as it had damaged the engine.  It's cost me �500.  But a friend of mine seems to think that because it hadn't gone very far it shouldn't have caused that much damage.  Oh well, I guess I'll just chalk it up to experience, as a woman I'm used to garages seeing me as an easy target!  At least I know to ask about the cam belt next time I buy a car :o)  Oh and funnily enough it's done 68,000 miles so I guess it was due to happen!
i dont know where they get their knowledge from but if a cambelt snaps - your car WILL NOT run and usually it damages the engine beyond   repair and you would be better off  scrapping the engine, if it got done up, it would cost a large amount of money, and you would have to weigh up whether to do it up or put in a re-con motor, whatever you did it WOULD be expensive, and only you could decide as to whether it was worth spending a large amount of money on it, hope this helps.

the engine idles at around 800, thats 800 turns every 60 seconds, that' a lot of turns, drive away and that speed at least doubles, more if you boot it, so even sitting idleing, when the belt breaks will do the same damage, Nowadays, nobody really repairs an engine after a break, well not on older cars, it is often cheaper to replace the whole engine, a second hand engine can be got for about �250, and fitted for maybe another �100.

To fix it, they would , as was said beofre , maybe try a belt on it, you might be lucky, but usually not, there are very few, engines that do not suffer catastrophic damage when a cam belt breaks, next is to remove the head and see how bad the damage is, any bent valves need to be rplaced, thhead would need to be cleaned and probably pressure tested, a new head gasket set can cost �100, and the labour is frightening, the vavles alone can cost upwards of �60 each and there are at least 8, then the pistons have to be checked for damage, and then it all has to be put back together and a new belt fitted, new oil and filter, new antifreeze, very expensive, I normally simply recomend a replacement engine if a belt breaks, it's much cheaper in the long run, of course it depends on how old the car is and how many miles it's done.

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