Help me estimate true odds of timing belt failure

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The idea that timing belts must be changed at 60K seems a little suspect to me given the improvements in manufacturing over the past 20 years. Yeah, I know you can't tell if it's about to break beforehand, rubber deteriorates, the expense of repairing bent valves etc. is many multiples the expense of proper preventive maintenance, etc. But, the cost of a timing belt change is often about $500 these days, and worst cast expense of fixing a typical engine with catastrophic belt damage is normally less than $5,000. So, when you you suppose the odds of timing belt breakage approach 10% for the typical engine?
 
LOL! You delay the timing belt change, you run the risk of damaging the engine if it's interference design (e.g. Honda), simple as that.

Yes, material quality has improved a lot over the past 20+ yrs but the fundamental practice still calls for a pre-defined TCI (timing-belt change interval) to be set, and it's typically based on the auto manufacturer's recommendation.

You can change sooner than what they called for but if you let it goes beyond their recommendation, the chances of belt-related failure will increase substantially.

There's no hard/fast statistics you can refer to on the internet.

Q.
 
Plus the tow charge and the time on the side of the road the extra cost of the rental car if needed adds up. you buy a car with a timing belt you pay for the timing belt expenses.I would go by the recommended intervals of the manufacture. You may get lucky, I never do.
 
The timing belt broke on my mom's 91 Ford Escort GT 1.8L at 90,000 miles. I was driving with the cruse set at 60 MPH and it just quit and coasted to a stop. That was a non interference engine and no damage was done.
 
It depends on the application.

Some applications have had issues with premature timing belt failures. Others have not.

With that said, what kind of vehicle is this?
 
The 60k limit is partially set low by the mfr to remove their liability. age plays a part also. a friend of mine roached his VW motor at around 90k due to the belt. on the first car I had with a timing belt, I replaced the belt at 85k. it looked great - but the car was only 5 years old. since then I have never changed a belt. fingers crossed.... of course, I try hard to purchase engines with timing chains... you can also frequently get a motor replaced for around $1k with a low mileage junkyard motor.
 
I am having problems determining when to replace the timing belt on a 2001 Lexus RX300. Has 35,500 miles. Gets about 3,000 miles put on it a year. Lexus recommends a 90,000 mile interval. That is about 18 years from now. I am thinking 60,000 miles. The exterior components look very new. However, this is the sludge prone motor. Not sure if that effects belt life.
 
I've done work on quite a few cars for myself, family, and friends. I myself have NEVER seen a BELT fail at less than 100K. My mothers 98 mazda 626 had an idler failure at 28K. There was a recall on that... She was never notified. I called corporate and asked what they would do... NOTHING! I try to change them out at about 100K. It may bite me one day.
 
A friend's GTI has 175k or so on the original belt.

He also has no sludge in that 1.8T, from running M1 0w-40.

Perhaps he is just lucky...
 
Depends on what type of vehicle you are driving. Most timing belts I've seen break are a result of something associated with the belt, not the belt itself, i.e a bad w/pump, tensioner, idler etc or an oil leak on to the belt causing it to weaken. If youe engine is a non-interference design I would not be overly worried about changing it exactly when the mfg says to, but with an interference engine, don't take any chances.
 
A timing belt doesn't usually break. They lose about 10 teeth that are all by each other and that stops the cam because the crank is just spinning on the toothless belt.

My friends PT cruiser had it's belt strip at 96K. The valves don't hit the pistons on this one...........The intake and exhaust valves will hit each other if you get them out of sinc and hers did.

I had the belt done on my moms car @ 75K because the belt was 10 years old.
 
Your car, your risk.

Look at a typical bell curve. Some belts will fail the day after they are put on (not many), some will fail a long, long time into the future, most will fail in an average time.

OEMs try to make your replacement interval on the very safe side of average.

If you've got the failure data, you can decide on the risk profile that you are happy with, and choose some number.

Knowing what I know about cars 'though, it will fail in the most catastrophic way possible at the most inconvenient time and place, the weekend before it was due to be changed, and the parts and tools will be in the garage waiting for you to get home.
 
When I had a 96 Honda Accord the belt failed on the Highway with the cruise on with 56,000 miles. Change it.
Nothing I own now has a belt, everything has a chain. The Honda ruined it for me.
 
I know people that have had the TB fail on them with interference engines. Some just replaced the TB and got away with it and others couldn't. Had to replace the head too! When you take the vehicle into a mechanic, you have to take his word that the head need to be replace also. Doing the job yourself, you know wheather or not the head/valves were destroyed in the process.
 
Don't know, but the real question is how soon. How soon? Don't know that either, but much sooner than a timing chain. I think I ran a Valiant to 120 K and 10 years, a Phoneix to 140K and 11 years, a Grand Am to 180K and 10 years, and an Ecotec to 165K and 8 years all on the original timing chain with no problems. My 77 truck only had 145K on its original chain. I don't know how much difference in original cost between a belt and a chain, but it has to be much less than the first belt change.
 
I would change it when they recommend changing it, if I were to stretch the interval I would probably not go past another 20,000 miles. So it they call for a 60K change 80K would be the max.

The belt could last the life of the car or break at 60,001 miles. I don't like getting stranded, especially when the maint. intervals are clearly stated. JMO
 
Originally Posted By: newpassatt
Most timing belts I've seen break are a result of something associated with the belt, not the belt itself, i.e a bad w/pump, tensioner, idler etc or an oil leak on to the belt causing it to weaken.


EXACTLY. I've never seen a T-belt failure just out of the blue with no apparent cause but the belt itself. Like you say, it's the associated components that cause the belt to fail. On vehicles prone to this type of behavior (bad idlers, tensioners, etc), you'll want to follow the recommended intervals or sooner. I know from following other forums, certain Daewoo 4cyls used in 4cyl Isuzu Rodeos, certain Chevy Aveo's and of course the Daewoo line would get wobbly idlers causing the belt to pop off and crash the intake valves.

Joel
 
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