How long does a cam belt really last?

[OneEyeJack]

An independent mechanic told me he serviced a Toyota pickup with the 4.7 V8 engine at 250K miles, one owner. He discovered that the timing belt and associated bits like the water pump had never been serviced or changed out. The belt looked a bit frayed with the occasional belt tooth partially missing or damaged but still the belt was working.

The owner had the plugs changed by a mechanic and 100K but passed on any other work. He also changed the Castrol GTX 5w-30 oil every 3K miles himself and changed the Toyota pink with Toyota pink from the dealer with just a drain and refill every 50K, that is not all the coolant was changed at any one time. He did the same drain and refill with the automatic transmission fluid using Castrol Transmax.

So, it the usual 100K or so belt life a very conservative interval?

 

[jeepman3071]

It usually lasts until it breaks.

I knew a few people in college who owned timing belt cars from new that had well over 100k miles and the timing belt had definitely never been done. 100k is a good conservative interval. I think a lot of it has to do with climate, miles driven daily, quality of the parts, etc.

If I had a timing belt car, I'd rather change the belt as a preventative instead of risking engine damage.

 

[mclasser]

My Accord's original (unbeknownst to me then) timing belt came out looking great @192k. Of course, this is the exception, rather than the norm.

At least with a non-interference motor, there won't be catastrophic damage if the belt decides to skip town; you'll only be stranded at an inopportune time/place.

 

[Jetronic]

Originally Posted By: OneEyeJack
An independent mechanic told me he serviced a Toyota pickup with the 4.7 V8 engine at 250K miles, one owner. He discovered that the timing belt and associated bits like the water pump had never been serviced or changed out. The belt looked a bit frayed with the occasional belt tooth partially missing or damaged but still the belt was working.

The owner had the plugs changed by a mechanic and 100K but passed on any other work. He also changed the Castrol GTX 5w-30 oil every 3K miles himself and changed the Toyota pink with Toyota pink from the dealer with just a drain and refill every 50K, that is not all the coolant was changed at any one time. He did the same drain and refill with the automatic transmission fluid using Castrol Transmax.

So, it the usual 100K or so belt life a very conservative interval?

Depends on the engine, and on the conditions the engine gets used in. Ttavelling the ionterstatze in top gear puts lessstressand revolutions on an engine than city and rush hour traffic.

I've seen belts fail before the recommended interval....

 

[Cardenio327]

The timing belt only lasts as long as the tensioner and idler bearings last. That's why you can sometimes get away with not changing the original belt, but if the belt has already been changed you probably shouldn't risk it because you can't trust the replacement bearings to last longer than the recommended belt change interval.

Some Renaults recommend the timing belt to be changed every 37,500 miles in normal service and every 25,000 miles in severe service. These cars are known to suffer catastrophic timing belt failure around 45,000 miles when primarily driven in heavy traffic.

I've heard that Ferrari timing belt interval is 22,000 miles and that they will fail soon after if not changed, but I don't know if it's true or not

 

[Olas]

I like to go by 5 years/60k miles, whichever comes first. If the date/mileage of the last change is not known or recorded a visual inspection and tension check decides between urgent, sometime this year, or about 4 years.

When I bout the scirocco in 2007 it had 46k miles and 25 years on the original belt. Changed it as soon as a new belt&tensioner came in the post. With my relatively low miles I'll stretch to 7 years/80k miles.

 

[Kestas]

Like Cardenio said, it's usually the tensioner or idler pulley that is the problem. Belt failure is more commonly from bearing seizure than from the belt itself.

 

[BrocLuno]

It has to do with operating conditions and original belt construction. If it gets oil on it or coolant or any sort of solvent, it will have a much shorter lifespan. If it gets hot over and over as in AZ in the summer with the A/C going full blast so the under hood temps are very high, it will fail sooner. If the tensioner is off a little bit so it is either to tight or to loose and has a bit of flutter, it will fail sooner.

 

[zzyzzx]

My last one lasted 97K miles before it broke and left me needing a tow.

 

[WylieCoyote]

A co-worker who owns a 2010 Kia Soul with 130K+ struck up a conversation about her vehicle's maintenance, and I asked her if she'd had her timing belt replaced yet. I got a blank stare. She took it to her mechanic two days later, and he said she was lucky she made it. Teeth missing and frayed.

I have been very glad to see timing belts fall out of favor. Nothing but a ticking time bomb....especially for those who aren't aware they have one. I traded in a 1994 Eclipse in 2000 and I heard through the grapevine that someone bought the car, and the belt broke on their way home with it. Nice repair bill for the dealership, nice bullet dodged for me.

I think it's all about climate and city vs. highway driving that determines when you'll find yourself stranded aside the road.

 

[Chris Meutsch]

Time (and a pulley/tensioner failure) will kill a cam belt vs. mileage.

I've seen one after two years and 100K and it actually looked BETTER than when it went on.
I've had one fail and take out the top half due to a NEW tensioner failing.

 

[555]

You should not judge the condition of a timing belt by looks alone.
Partially missing and damaged belt teeth are about as bad as it gets before failure. If it's an interference engine, the belt snaps and pistons meet valves.
If it's a non-interference engine and the belt snaps you will be stranded but your valvetrain will live.

 

[WillsYoda]

My 98 1mzfe timing belt was on for 135k and could have gone longer. It is non-interference, so I was not worried.

 

[kschachn]

Originally Posted By: 555
You should not judge the condition of a timing belt by looks alone.
Partially missing and damaged belt teeth are about as bad as it gets before failure. If it's an interference engine, the belt snaps and pistons meet valves.
If it's a non-interference engine and the belt snaps you will be stranded but your valvetrain will live.


It's not just engine damage, if the belt snaps on the freeway you could end up in a nasty accident.

And I agree, missing teeth on the belt indicates it was run WAY too long.

 

[Rick in PA]

Belt life is a mostly factor of how tortuous the belt path is and run time. Imagine a belt that runs over two very large pulleys, it would last about forever. Imagine a belt that runs over many small pulleys and gets flexed backwards a bunch of time, the belt wouldn't last long. The engineers can calculate out belt life expectancy.

My wife had an Ford Escort that snapped it's belt at about 60K miles. Then I found out they typically lasted 50~60K miles. Not an interference engine, so more of an annoyance than a problem.

I had a friend with a Renault Alliance, it snapped it's belt at something like 70K miles. Problem was it was an interference engine and the engine was toast. Car in nice condition, but a badly damaged engine. A lot of Alliances, in nice shape, ended up in the junk yard, there were no "junkyard motors" to resurrect them.

I just got a Neon with 97K miles and am going to pro-actively do the timing belt. They seem to have a belt failure window of 100K to 150K miles, which seems about typical.

 

[edwardh1]

my 79 vw rabbit , belt broke twice at 60,000 miles, both failures were at morning start up. no damage, easy to change

vw had lots of other issues.

 

[4WD]

Well since each OEM should post when to change (did my Chrysler at 100k before it broke) I'm left to wonder how many of the failures were before the OEM change out point ?

 

[quint]

The belt in my Corolla went 315,000 miles before it finally gave up on the highway. It was my dads car, he had bought it new and I was the only person to ever maintain the car so I know it was the original belt. He is old and drives like.... well, an old person. So it had a pretty easy life up until that point. Upon disassembly to put the new belt on, I discovered the belt was intact, but the idler pulley had come apart. The belt itself had a deep crack between each tooth but was still in one piece.

The belt on my Sequoia was changed at 95,000 and other than some dust it looked very little different than the new one I put on it. The idler pulley however had lots of play so I was glad to be changing it.

 

[Linctex]

Originally Posted By: Rick in PA


I had a friend with a Renault Alliance, it snapped it's belt at something like 70K miles. Problem was it was an interference engine and the engine was toast. Car in nice condition, but a badly damaged engine. A lot of Alliances, in nice shape, ended up in the junk yard, there were no "junkyard motors" to resurrect them.


You could *maybe* assemble 1 good engine from 2-3 bad ones. Not all the valves and pistons will "take a hit", correct?

 

[OneEyeJack]

I changed the timing belt, pulleys and tensioner along with the plugs on my 03 V8 4Runner at 100K and the belt looked almost like new. The teeth did not show signs of wear or frayed edges.

I really like the idea of timing marks on the belt. Since I don't work on cars every day anything like that that helps avoid a mistake is good.

Now I wonder about the serpentine belt......