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Cam belt roulette.
https://forums.tipec.net/viewtopic.php?f=25&t=19067		 Page 1 of 1
Author:  white944 [ Fri Dec 26, 2014 11:01 am ]
Post subject:  Cam belt roulette.
OK, here's the thing.

As far as I am aware, the 944 belts have a recommended change every 40K miles / 4 years. These cars were born in the 1980s when this was not unusual, a lot of regular cars had similar requirements. Fast forward 30 years and things have moved on. Many cars now have recommended belt changes at 120K miles / 10 years or beyond, presumably due to advances in the materials used in the belts.

So...... If One purchases a replacement cam belt for a 944 in 2014, are belt manufacturers holding back some inferior 1980s materials to make 944 belts, or are the replacements made from far superior stuff that negates the necessity for such frequent changes?

Discuss :mrgreen:
Author:  scam75 [ Fri Dec 26, 2014 11:49 am ]
Post subject:  Re: Cam belt roulette.
Dunno. A lot of bluster about this topic. I have recently acquired an S2 cab. 9 years since belts were done. I refused to start the thing except the day I ran it into my mates garage to do the belt change. Now not that you can spot a belt about to snap or anything, but the 9 year old belts that came off looked as good as new! Read into this what you will.

However you must balance this against the results of a belt failure which is catastrophic. I do however think we err well on the side of caution with the 4 year yardstick we go by.

Stuart
Author:  Waylander [ Fri Dec 26, 2014 12:12 pm ]
Post subject:  Re: Cam belt roulette.
total common sense, belt failure 3K two belts £70 no brainer

and don't forget to examine the gears they wear too, worn gears much faster wearing belts....
Author:  white944 [ Fri Dec 26, 2014 12:52 pm ]
Post subject:  Re: Cam belt roulette.
I'm going to do mine even though they have only 10K miles on them, because they are the last recorded change was 9 years ago and the car has been idle for 5 years. Obviously, I'm not suggesting everyone ignores maintenance, especially when a catastrophic failure is on the cards, however, I do suspect the new ones would be good for 60-80K with no problems. The manufacturers and Porsche specialists wouldn't want us to know for obvious commercial and liability reasons, but it's an interesting subject. I haven't noticed Ebay awash with 944s for spares and repair due to belt failure, and there are a lot of neglected cars out there. Has anyone here had belt failures soon after 45K? Would be interesting to find an insider in the automotive belt industry who knows what's what.
Author:  jackois [ Fri Dec 26, 2014 2:43 pm ]
Post subject:  Re: Cam belt roulette.
I have a modern Fiat 500 as well as my 944 S2 & that has a recommended change of cambelt at 4years.... non interference engine as well!
Author:  AlpineTurbo [ Fri Dec 26, 2014 3:18 pm ]
Post subject:  Re: Cam belt roulette.
IMO it is not that easy ;).

I now own a car in which the engine type had a fierce reputation for snapping cambelts. From looking at Ford's schedule from when it was in a MkIII Escort to a MkIV the interval was extended by 5,000 miles . Whether that was down to the engine tensioners being superior or Ford simply gambling on things is unknown. I do know however that I have never let a CVH engine see 30k on my ownership before the cambelt is changed again (they were known for snapping belts as low as 25,000 miles). The Zetec which came out at the time had intervals of 60,000 miles between belt changes.

Many people felt that the reason why such cars snapped belts was due to the belt loading and the runs it took in addition to other factors (cam gear tension (not just the belt but the ease of turning the pulleys etc.). My point is that engines have changed quite a bit as well in that time. VW's belt on the Passat PD engine for instance is twice as wide as most other belts (it almost looks like the cambelt was designed to drive a supercharger!). Some people felt due to this that the belt could go on longer than what VW suggested but many forgot that the cambelt also drives 4 injector pumps directly off the camshaft...). Another point about differing designs.

BTW, quite a few modern cars don't make it that far. As an example my sister's Mondeo had her cambelt changed at 125,000 miles where we assume the original belt was changed at that time (it came with a full Ford history with no mention of the belt ever being changed). However, a number of ST peeps (with the same 2.5 Volvo engine) had had belts snap at 60,000 miles, with many questioning the very high interval from Ford.

It's horses for courses really, but personally I would stick to what Porsche say (I believe it is 48,000 miles at 5 years). I have had a 944 with the same belt on it for 5 years (it was wet however when it was removed due to an oil leak) but it was quite loose when it was removed and the car had only covered 20,000 miles in that time.

If you wish to know of long life belts you should see Ford's EcoBoost 1.0 engine. That belt is designed to be in the engine for the life of it (it is a wet belt). Now that is quite interesting ; no, the belt looks quite different to any other cambelt I have ever purchased.
Author:  Tabman [ Fri Dec 26, 2014 3:56 pm ]
Post subject:  Re: Cam belt roulette.
However I do recall some 8 years ago we were running a fleet of volkswagen lt35 and the recommended belt change was originally 100k miles.we had one go at 95k and then another go at 83k. Vw changed the service interval to 90k and then 80k. To be fair , they did make substantial contributions to both vehicles repairs.

Toby
Author:  Masher [ Sat Dec 27, 2014 9:54 am ]
Post subject:  Re: Cam belt roulette.
Is the critical factor mileage (wear) or time (degeneration/decay)?
Cheers
Mick
Author:  Brett928S2 [ Sat Dec 27, 2014 11:36 am ]
Post subject:  Re: Cam belt roulette.
Masher wrote:
Is the critical factor mileage (wear) or time (degeneration/decay)?
Cheers
Mick


Hi Mick :)

That is a VERY good question... which is really what this whole thread is about....

On my 928, the belt should be changed every 4 years (mileage doesn't matter, so whether its done 100.000 miles or 1 mile in 4 years, it should be changed)

Now that should imply its deterioration, but our belts are not exactly standard on a 928 as they are around 7 FEET long.....

Personally as an ex race mechanic, my best advice is this.... if you do not know when a belt was last changed ... change it NOW....

And change it at LESS than the manufacturers figures.....

I say that having changed LOTS of bent valves on engines , some of which were interference engines AND some which were MEANT to be non interference !!!

Hope this helps,

All the best Brett :)
Author:  AlpineTurbo [ Sat Dec 27, 2014 12:01 pm ]
Post subject:  Re: Cam belt roulette.
Masher wrote:
Is the critical factor mileage (wear) or time (degeneration/decay)?
Cheers
Mick


IMO it depends.

Age is a big thing. Rubber does decay with time, there is no doubt about it. However, the mileage also does account for belt wear, hence why two figures are given for belt changes :). As said, is it really worth trying your luck given the consquences? :).
Author:  Greggers [ Sat Dec 27, 2014 6:15 pm ]
Post subject:  Re: Cam belt roulette.
Its not simply the rubber that ages but the stuff inside that gives it its tensile strength which of course invisible.. Belts on cars - or bikes and Ducatis are top of that list - that have been standing for any appreciable time can 'set' over the profile of the pulleys making that an immediate weak spot. That's why you find belts that look OK but just break....the belts that wear out as a result of thousands of miles will show obvious signs of abrasion and scuffing.

My daughter brought an old but daily driven Picasso which had 175k on the clock on the original belt and clutch! Needless to say it got sorted sharpish.
Author:  944s2Fla [ Mon Dec 29, 2014 10:09 pm ]
Post subject:  Re: Cam belt roulette.
Part of my January shopping list,176,000 miles with 1 recorded change at 120,000, any other" while your in there "jobs ,to be done alongside this??
Author:  coolpaul [ Tue Dec 30, 2014 4:02 pm ]
Post subject:  Re: Cam belt roulette.
Don't know if it's just in this area - but most cambelt failures we have towed in to the garage are from early morning start-ups !
Customer just got in turned the key and 'what's happened' ?

Quite commonly showing very little signs of ware / age.
Author:  AlpineTurbo [ Sat Jan 03, 2015 11:41 am ]
Post subject:  Re: Cam belt roulette.
coolpaul wrote:
Don't know if it's just in this area - but most cambelt failures we have towed in to the garage are from early morning start-ups !
Customer just got in turned the key and 'what's happened' ?

Quite commonly showing very little signs of ware / age.


The belt loading is the highest at low RPM, when the valves/springs make the camshaft a little more reluctant to turn, leading to more stress placed on the belt. This is one reason why it is suggested that town cars have their cam belts changed sooner rather than later.
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