A friend and I changed the timing belt on his 2000 Accord V6 EX today. It is the first one we've ever changed. We figured we could save a fortune by changing them on our other Accords (he has another 2000 and I have a 2001). The car we changed the belt on has 135,000 miles and the belt had never been changed before. When we got the belt out and compared it to the new belt, we could find almost no difference at all. No cracks, no fraying, no perceptible stretching, no oil on the belt, nothing abnormal at all. We turned the belt teeth-out and bent it at a tight radius to see if we could find tiny cracks. None. This made us question why we should be changing the belt at all. We were thinking it might be good enough just to inspect the belts periodically.

I've seen posts from people who've had their timing belts break...I wonder how often this happens and whether or not the belt shows signs of wear long before they break.

Thoughts?

 

The reason you change the belt, before it breaks, is to prevent engine damage. Honda engines are interference engines. If belt breaks, the valves will hit the pistons cause valve damage for certain and possibly piston/cylinder damage.

Why does a used belt look almost as good as a new belt? Because the TB change interval is deliberately set well below the mean failure time/mileage to insure a very high probability that the belt does not fail before the TB change interval is reached. Probabaly something like 10^-5 or 10^-6 is likely target, maybe higher.

The belt is not the only issue. The bearings in the tensioner assy are probably at least as risky for failure as the belt. Also water pumps have been known to lockup, which would cause a TB failure.

Lots of good reasons to change on time/mileage interval recommended by Honda.

A belt in a good system w/i TB recommended intervals is unlikley to show any significant wear. I've pulled at least 6 belts and none showed any significant wear indications. I did find one tensioner bearing that was growling and would certainly not have gone another TB interval. Car was on 2nd TB change and idler probabaly was not changed earlier.

When you do TB change, change all tensioner bearings and water pump for maximum security.

good luck

 

Thanks, TexasHonda. I agree the belts must get changed before failure. I can't imagine (ok, I really CAN imagine) how much it could potentially cost to repair an engine whose timing belt broke on a sprint to the redline. I also agree with your suggestion that the manufacturers of both the belt and the car are leaning to a wide margin safety when they recommend belt change intervals. I'm sort of wondering how far I can push this before putting myself in real danger of a failure. My Accord has 142,000 miles and I cannot recall having anyone change the belt...in fact I'm pretty sure it's never been changed. My friend's cars have 135,000 miles and 160,000 miles or so, respectively, and until the other day neither of them had been changed. I'm just wondering if periodic inspection (by removing the front upper timing cover and splash guard and turning the engine over manually) would allow me to live with the current belt out to 200,000 miles or so. And if I did that, would I be flirting with a failure rate in the tolerable 1 in 10,000 range or the much scarier 1 in 100 range.

I may be looking at this with an eye toward risk-taking in light of how much work we've gone to in order to change his belt...when now that we know how to do it and have all of the tools, we might be able to get it done in under 8 hours. I'm milling that over in my head.

We also changed his water pump, and flushed and changed the coolant, while in there, but we didn't change the idler pulley or the timing belt tensioning pulley (we just transfered that from the old water pump to the new one). We also didn't change the front engine oil seal, which might well be worth it (though his wasn't leaking).

I'd still like to hear the experience of others. How many miles are on your timing belt? If it broke, how many miles did the belt have on it when it broke? Did you get to see the broken belt? What did it look like?

 

Environment is a big thing too. Hot climate. Short trips. Lots of idling.

Seems to me that cracks would begin to appear at the roots of the teeth, but maybe not until a matter of weeks before the teeth began coming loose. I think you'd have to inspect your timing belt every 2 weeks to be safe. That would be more of a PITA than changing it.

 

I don't think inspections would catch the most likely failure mode; a tensioner bearing beginning to drag/bind resulting in timing belt shearing lugs and slipping. This would happen pretty quickly, but might be accompanied by some bearing roar/whine.

Only Honda knows the statistics on how much cushion is built into the TB system; mean time to failure, standard deviation, etc, and I'm sure they won't tell us.

Remember there's a 7-yr time limit also and a 2000 is well beyond time limit also.

good luck