Cam belts

[geoffr]

Strange that it is a cam belt but a timing chain when both do the same job.

[MJB]

Feb 4, 2023 9:44:27 GMT geoffr said:

Strange that it is a cam belt but a timing chain when both do the same job.

I've always referred to them as a timing belt as that was what my uncle who was a car mechanic always called it.

[davem399]

I’ve been watching Saving Salvage on Youtube for a while now.  He is an ex Audi technician who “rescues” crashed and damaged cars, particularly Audis and VWs and repairs them.

Recently, he has been refurbing a couple engines, a V8 from an Audi R8 and a 4 cylinder unit from an Audi S3. These have got timing chains, and are very complex in both the arrangement and in the fitting of replacements. He also has several specialist tools which are needed for the job.

I found it interesting to watch him fitting the chains, which also included several guides, as well as idlers and tensioners.

[mick]

I have an Audi with a timing chain and have had several arguments with garages that wanted to change the 'belt'. One such place even insisted that I went under the car to 'see' the belt (on a ramp!). What was visible was the 'serpentine belt' that drives lots of accessories such as power steering, a/c alternator etc. Nothing to do with the timing or cam belt.

Mick

[geoffr]

Feb 4, 2023 10:11:18 GMT davem399 said:

I’ve been watching Saving Salvage on Youtube for a while now.  He is an ex Audi technician who “rescues” crashed and damaged cars, particularly Audis and VWs and repairs them.

Recently, he has been refurbing a couple engines, a V8 from an Audi R8 and a 4 cylinder unit from an Audi S3. These have got timing chains, and are very complex in both the arrangement and in the fitting of replacements. He also has several specialist tools which are needed for the job.

I found it interesting to watch him fitting the chains, which also included several guides, as well as idlers and tensioners.

Gets even more interesting when you include balancer shafts!

[andy]

Feb 4, 2023 9:44:27 GMT geoffr said:

Strange that it is a cam belt but a timing chain when both do the same job.

And neither controls timing (of ignition)? Cam seems like the more accurate term....or even cam timing.

FWIW on bicycles chains are more efficient at transferring energy, usually by somewhere in the region of a couple of percent. A few extra watts is less significant with an engine though.

[geoffr]

Feb 4, 2023 14:27:55 GMT andy said:

Feb 4, 2023 9:44:27 GMT geoffr said:

Strange that it is a cam belt but a timing chain when both do the same job.

And neither controls timing (of ignition)? Cam seems like the more accurate term....or even cam timing.

FWIW on bicycles chains are more efficient at transferring energy, usually by somewhere in the region of a couple of percent. A few extra watts is less significant with an engine though.

Andy, open the bonnet of your car and look at the cam cover, at the right hand end, as you face the engine, there is a blanking plug or, yours being an automatic, a vacuum pump. In 1986 when a predecessor that engine was used in the Saab 9000 that location was used for the distributor. So actually on early 9000s the chain did have something to do with the ignition timing.

[Kath]

No advice but when we were quoted £800 to replace the cam belt on our VW touran we ignored it. Cam belt went and killed the car on the way to collecting our daughter from hospital.

[mick]

Feb 4, 2023 12:20:20 GMT mick said:

I have an Audi with a timing chain and have had several arguments with garages that wanted to change the 'belt'. One such place even insisted that I went under the car to 'see' the belt (on a ramp!). What was visible was the 'serpentine belt' that drives lots of accessories such as power steering, a/c alternator etc. Nothing to do with the timing or cam belt.

Mick

Misled you - sorry. My car is a V6 and so it has two timing/cam chains. One for each leg of the V.

Does it really matter what they are called? The belt/chain rotates the cam shaft in sync with the crankshaft. That means that the timing of the pistons and valves is controlled so that said pistons and valves don't bash into each other (in what's known as an interference engine which in turn means an engine in which pistons and valves use the same space - but at different times!). Should the belt/chain break the consequences are often (usually) catastrophic for the engine.

Mick

[geoffr]

Feb 5, 2023 9:20:47 GMT mick said:

Feb 4, 2023 12:20:20 GMT mick said:

I have an Audi with a timing chain and have had several arguments with garages that wanted to change the 'belt'. One such place even insisted that I went under the car to 'see' the belt (on a ramp!). What was visible was the 'serpentine belt' that drives lots of accessories such as power steering, a/c alternator etc. Nothing to do with the timing or cam belt.

Mick

Misled you - sorry. My car is a V6 and so it has two timing/cam chains. One for each leg of the V.

Does it really matter what they are called? The belt/chain rotates the cam shaft in sync with the crankshaft. That means that the timing of the pistons and valves is controlled so that said pistons and valves don't bash into each other (in what's known as an interference engine which in turn means an engine in which pistons and valves use the same space - but at different times!). Should the belt/chain break the consequences are often (usually) catastrophic for the engine.

Mick

Some engines use a common chain for both banks some use a separate chain for each bank.

[MJB]

Until recently I used to buy cheap runarounds for £500 with 12 months MOT and then drive them until they died*. I'd usually get 2-3 years out of them until they required a big bill paying out, at which point I'd scrap them and start again. To the best of my knowledge none of them had had timing belt changes and all of them had done over 120,000 miles and none of them suffered a timing belt failure.

* There were some gems to be had if you weren't picky about make or model. There were lots of good cars that dealers offered peanuts as trade-in value. Sadly the government subsidy in the form of the scrappage scheme pushed the prices too high.

[zx9]

I first met overhead cams in 1980's motorbikes, at the time most of my friends the item in question a cam chain, I have just stuck with that terminology.
Today the actually valve timing of a lot of engines is only partly done by the cam chain, the actual timing and duration of valve lift is controlled by electro mechanical and or oil pressure regulation of the cam shaft positions, to the extent that at low demand the throttle body has little to no effect on airflow and mixture control.
Various names for it VVTI, valvetronic to name but two.

[mick]

Feb 5, 2023 9:54:36 GMT MJB said:

Until recently I used to buy cheap runarounds for £500 with 12 months MOT and then drive them until they died*. I'd usually get 2-3 years out of them until they required a big bill paying out, at which point I'd scrap them and start again. To the best of my knowledge none of them had had timing belt changes and all of them had done over 120,000 miles and none of them suffered a timing belt failure.

* There were some gems to be had if you weren't picky about make or model. There were lots of good cars that dealers offered peanuts as trade-in value. Sadly the government subsidy in the form of the scrappage scheme pushed the prices too high.

I've considered doing that myself but, until quite recently, I did high mileage and very frequent trips from the Garden of England to Manchester and/or Liverpool. Many of those trips were at the dead of night and I never quite had the courage to risk a breakdown.

I'm quite sensitive to the possibility of such an event because, when newly married, SWMBO became pregnant and we determined to drive from South Wales to Manchester in order to spread the news. Near Monmouth the crankshaft broke resulting in a bit of a nightmare and we lost the baby.

Mick

[Deleted]

I have decided to keep the car and have the cam belt changed. I have been quoted a price by the main dealer, which is consistent with my expectation and have asked for a price from a local independent garage. When I had the cam belt replaced on the Octavia I went to the local garage I have used on and off for years but it probably would have been cheaper at the main dealer. I won’t ask them to quote for the Fabia.

[zx9]

Feb 5, 2023 10:46:11 GMT @bazarchie said:

I have decided to keep the car and have the cam belt changed. I have been quoted a price by the main dealer, which is consistent with my expectation and have asked for a price from a local independent garage. When I had the cam belt replaced on the Octavia I went to the local garage I have used on and off for years but it probably would have been cheaper at the main dealer. I won’t ask them to quote for the Fabia.

Cool, don't let them just do the cam belt the kit should have tensioners / idlers and ask if the water pump is driven off the cam belt, if so have that changed at the same time as compared to labour costs involved the water pump is almost a consumable. VAG water pumps used to have plastic vanes which deteriorated and broke up over time, I don't know if they have improved them since my Audi owning days, I don't expect they have.