Timing Belts for 1.8 5-valve engines.

**John-NZ** · 09-10-2008, 09:01 AM

Much argument on European and North American Audi/VW forums about premature failures of VAG timing belts and tensioners.
Seems that British Audi importers have reduced the recommended miles/kilometres for replacement below what the factory recommends.
Of course, our American friends are eager to sue when belts fail prematurely. What many forget is that the issue relates to many models, and to other makes of cars, and that the belts and tensioners are all designed and manufactured by a few major North American and European belt specialists. My interest is in the 1997 1.8 litre non-turbo 5-valve engine used in the Audi A4, but it is relevant to all owners.
On the Aussiefrogs forums for Australian owners of French cars, "Alan S" quotes information printed on a timing belt box, that confirms that there are three generations of timing belt materials used over the last 8-10 years, with recommended life extending from 48,000 to 72,000 miles. Alan quotes these as- "1st Generation: (NEO) = Neoprene, fibre glass cords and nylon tooth facing. 2nd Generation:
(HTN) = High-Temperature Neoprene, fibre glass cords and nylon tooth facing. 3rd Generation: (HSN) = Highly Saturated Nitrile. Aramid fibre or fibreglass cords and non stretch nylon facing at higher temperatures with greater horsepower. A graph showing the heat resistence comparison is also interesting with Gen 1 showing at 105 degrees C which is increased to 130 for the Generation 3 belt."
So, if you order a new Timing Belt, it should be new stock identified as HSN materials, and a cheaper priced belt may have a shorter life.
I have turned up more information on this topic, for a later post. John.

**John-NZ** · 09-10-2008, 11:36 AM

I notice that some new car models are being promoted as having "Timing Belts that will last for the life of the car". Be nice if that meant a Lifetime Warranty, wouldn't it? Earlier generation belts would stretch with age, new generation belts fail by breaking or losing teeth.
Replacement recommendations for VAG vehicles seem to have moved down to 4 years or 60,000 miles/ 100,000 km or sooner, with annual belt inspections. Apparently there is much less wear with extended open-road driving and shorter trips with few stops and starts, than occurs if you have a daily stop and start commute on congested motorways and crowded city roads, which can halve the life of your timing belt (and other parts prone to wear).
We can all buy some peace of mind by unclipping the Upper Timing Belt Inspection Cover every 6 or 12 months, and rotating the crankshaft pulley with a socket on the central bolt. Examine your timing belt for damage (delamination, fraying or cracking when twisting the belt by 90 degrees). Not so easy to examine the belt tensioner, unfortunately, which might need complete dismantling of all belts and pulleys. The Serpentine external drive belt and accessories belts should also be checked for damage.
A seized bearing in the belt tensioner is not uncommon, due to lubrication drying out or overheating, and the nylon teeth can crack or disintegrate. Most engines are "interference clearance" now, so that valves will strike piston heads if the valve cam stops turning due to timing belt damage, and the damage can be disastrous. Versions of my Audi A4 1.8 litre engine with 5 valves per cylinder were also an option in some Audi A3 and A6 cars, VW Passats, and Skodas. Service information that I have suggests that the Longitudinal-mounted 1.8 engine had the water pump driven by an external accessory belt, but the Transverse engine mounted crosswise (A3) had the water pump driven by the Timing Belt, and the increased load and wear results in a shorter timing belt life (and disaster if the water pump seizes). Apparently the design of the timing belt and tensioners on the 1.8 5-valve engines similar to my Audi ADR version were changed in 1998, because of premature belt failures. You might find this document from Gates Corporation (Europe) of interest.
See http://partsforallcars.com/spares/pdf/gates010.pdf for full bulletin. Apparently Gates and VAG decided to redesign the Timing Belt drive on these Passat and A4 1.8 engines because of failures. The wax-filled actuator on the belt tensioner has been replaced with an oil-filled actuator, the belt with 152 teeth has been replaced by a different stock belt with 153 teeth, and the new tensioner has a spacer washer 3mm thicker than the old design, and a different idler. The upgrade replacement kit contains more parts, so you can expect a higher price (well, it is for Audi and Volkswagen, isn't it?). Any of the experts out there care to share their thoughts and experience on this topic? The rest of us will continue to drive and hope for the best! John.

**Bug_racer** · 09-10-2008, 12:30 PM

The old 152 teeth timing belt was discontinued long long ago . These only came out in 1996-1997 on Audi A4s , Ive never seen any on a 1.8t passat . I think I may have kept one as a novelty item cause they look so clumsy and chunky compared to the updated units . So I guess you dont need to worry about these .
As for the timing belts themselves , I no longer "inspect" timing belts for age . Your meant to look for cracks or signs of ageing but if you have a small oil leak it actually makes the belt look shiney and more newish looking when in fact the oil is breaking down the belt a lot quicker than normal .
I think all the "worry" about belts breaking is an O/S thing , Ive seen very few belts break here and its more often the chain drive on the other side of the head that fails than the belt itself .
My opinion , stick to 4 years , 90k km and you'll be right . Oh and change the water pump when you do the timing belt

**No457 Snowy** · 09-10-2008, 01:46 PM

Hey Seb, so should you be looking at changing the belt at 4 years old even with just 60,000km done?

Mines a 2004 model so that's where I'm at now.

Snowy

**dubbed** · 09-10-2008, 01:53 PM

What will actual happen if the belt snaps or the pulley/s seize?

**No457 Snowy** · 09-10-2008, 01:58 PM

Originally Posted by dubbed

What will actual happen if the belt snaps or the pulley/s seize?

I know if that happens lots of fast moving metal bits hit each other, change shape, and then stop moving.

Snowy.

**dubbed** · 09-10-2008, 03:19 PM

So a full ground up rebuild would be in order? New pistons, valves etc? What does the 1.8T cost to rebuild? lol I hate to think!!

**Golf Loon** · 09-10-2008, 07:28 PM

You should seriously think about doing our belt at 60ks or 4 years. It time.

1.8T would cost a couple of grand easy to rebuild. the bottom end bearings are butterbearingas are are $350 from VW.

**John-NZ** · 10-10-2008, 07:52 AM

This is what your valves would look like after breaking your timing belt at 100kph.
http://www.audiworld.com/tech/eng23.shtml
If the top of the pistons shatter, who knows where the debris goes - one American had the metal fly into his turbo.