Cam Belt??

Question

Why oh why is such a major part of a working engine made from a piece of rubber? Surely there must be a better option.

Answer 1

Actually, the rubber encases steel and/or kevlar belts. It's much quieter than chains, so it helps manufacturers keep to the mandated noise pollution regulations. Its also much cheaper to make. Chains used to last much longer, but it cost a lot more to change them when they did wear out. Also, since the chains had to be lubricated with engine oil, they couldn't be inspected for wear - you had to rely on hearing the noise and knowing what it was. This also means another gasket that could start leaking - especially since it would have to span from the oil pan all the way to the head (if you have DOHC.) Where the gasket crosses the join of the pan to the block, and the block to head, were often oil leak problem areas (look at a mid-70s Alfa Romeo to see what I mean.)

Answer 2

It is the cheap option for the manufacturer, but replacement can be expensive for the owner. An internal chain makes the engine more expensive and internal gears even more so. The latter is almost unheard of on cars now, but some quality marques like Mercedes use a chain. Always check the price of cam belt replacement when buying a car. It varies enormously. On an Audi A4 diesel with aircon it is around £800 at the dealers. On one Alfa Romeo it is a four figure engine out job. This is owing to accessibility problems. Something some manufacturers never seem to worry about.

Answer 3

I've been saying the same thing for years. Chain driven cams are a much more reliable way to go, especially in the day and age of transversely mounted, interference engines. Something like an eagle talon (I refer to them a lot due to their absolute terrible design on just about everything) would require $700 to change the belt... not including the belt. Something like a porshce 944 (another interference engine) can be $2000. Chains are the way to go, but belts are simpler for the manufacturer.

It should be mentioned that interference engines (for those who don't know) are engines that, without proper valve timing, will pound the valves into the top of the pistons... VERY expensive and devastating. When the timing belt goes, you get a barrage of valves running kamakazee missions into the piston tops.

Answer 4

Cam belts are not just rubber - they are reinforced with steel or composites.
Belts are cheaper than chains, but are used mainly because the y produce less noise, and don't require lubrication.
Some manufacturers do use chains, and gears (even more expensive and even noiser) are common on racing engines.

Answer 5

Totally agree
mine went about 3 weeks ago,cost me £500.Which is quite a lot of money for me.
i have a 1.9 diesel.Good job is was only 8v though or it would have been double.
You have to look about i phoned around a few garages and got quotes for up to £1000 and more to be fixed.So what i paid doesn't seem to bad in the end.

Answer 6

I agree. They used to use chains. I believe now that some manufacturers have started using them again. I think the main reason was to reduce friction and also noise. Additionally it gives more work to garages every 70,000 miles or so.

Answer 7

there is, some cars are chain driven. They probably don't do it to all cars coz it costs more money.

Answer 8

no there really isn't