Why do California timing belts last longer ?

No they are the same belt. Calif and Mass passed laws saying that timing belts had to last 100K. So Mazda changed a line in the owner's manual and VOILA, the timing belts in those states are now "good" for

100k.

That doesn't mean some won't fail before 100k, of course. Mazda's choices were a) eating a few timing belt jobs under warranty, or b) not selling cars in California (Massachusetts is probably inconsequential). A classic, purely-economic business decision...and a no-brainer.

Of course not. We had someone on here whose stock engine gave out at approximately 40K miles, very unusual for a miata. I decided to replace my belt halfway between the two, at about 80K to

85K miles. I have heard of very few, if any timing belts that have failed before that time, though once again, being a mechanical part, a defective one could break at any time.

Pat '96M

Lanny: There's plenty of Miatas here in Massachusetts, that's how we get around when peeping at the leaves on all those country roads. Frank Sawin

No kidding? I thought all those Miatas came from New Jersey and New York...

At 60,000 -- From what I've seen-- The belt should be normal with a noticeable amount of rubber dust. The belt tooth profile will show slight rounding when compared to a new belt. The Idler and Tension pulleys should be checked for play. Your call on the water pump. At 100,000 if the belt was not replaced at 60,000. -- More rounding on belt, possible delamination just starting. Replace pulleys, water pump, tension spring, etc.

Lanny: They are here too, tourists from NY and NJ, we sell them pretty colored leaves to take home. Frank Sawin

That seems to agree with my observations. As a point of reference:

Our kids have a 1997 Mazda Protégé which we bought used. The previous owner had never changed the timing belt so I did it at a little over 100K. On this belt, the base material could be seen in the flat areas between the teeth. Clearly, there was more wear than the two that I replaced on the Miata. I would agree from this experience that 60 - 80K sounds right for the Protégé as well as the Miata.

Next one coming up is the 60K belt swap in the 2000 Audi A4.

Righty, You are too funny ;-)

Lefty ~Cissy :-)

Re-read what it says in your manual about the inspection. Mine says there are two needed before 100K. That's what gives Mazda an out when they break under 100K. Not that you can see anything anyway but if you get it inspected, I'm sure they'll tell you to replace it.

Good point. What do you think an inspection would involve? Probably removing the belt and checking it out. Here is what my '90 workshop manual says about inspection:

" 1. Replace the timing belt if there is any oil or grease on it. 2. Check the timing belt for damage, wear, peeling, cracks, and hardening. Replace the timing belt if necessary."

Let's say you do this at 60K or 80K miles and the belt seems to be OK. Would you put it back in? Let's see a show of hands. No hands. That's because nobody in their right mind would do all that work and not replace the belt. Even if you do this inspection without actually taking the belt out; by the time you are that far into engine disassembly, you would simply replace it.

Can't you just remove the cam cover to see the condition of the belt ?

Actually, you can. By this shop manual criteria, belts that I replaced at

80K miles would look just dandy to anyone took off the cam cover or, for that matter, actually took them off the engine. The only way you could begin to judge wear would be by noticing the accumulation of rubber dust (understanding, of course, the source of the dust), but this was not provided as a measurement of wear.

Also, I am not certain how one would check for "hardening" by visual inspection. Whatever "hardening" actually is. The manual doesn't say.

I think a previous poster got it right. Without removing the cam cover at all, the Mazda shop could tell you that the belt needs to be changed, just by looking at the odometer. I do think that a visual inspection that revealed a damaged, peeling or cracked belt could well save someone a lot of grief. We know that for every belt that goes 120K miles, there is probably one that gave it up at 40K, so I think you have a good point. The shop manual does not suggest visual inspection; it only says to replace the belt at 60K miles and that engine damage may result if you don't. Strange thing to say for a non-interference engine.

By inspection with the cam cover off, one would have to rotate the belt, looking at each visible section until complete. On my '90, replacement of the cam cover requires blobs of RTV at indicated points to ensure the gasket does not leak. Perhaps replacement of the cam gasket would be a good idea, since it is so easy to do.

Ken

Well Ken, I think for the most part, you ae correct. The BIGGER problem is the belt tentioners. At 120,000 miles, you will "need" to change them ! If you can spin them (with the belt off), they are shot! Last year, I saw a '97 that the tentioners had failed and came out thru the front cover and into the radiator. Damage to the engine it's self, was only replaceable plastic parts. Damage to the fan and radiator was total ! Many tentioners are gone long before 100,000 miles and just waiting to fail.

Bruce RED '91

If you can "spin" the tensioner, then there is no grease left in the bearing and indeed it will soon fail. It is possible on many tensioners (I haven't done a Miata yet) to pry carefully around the edges of the seal and then clean and repack the bearing. With fresh high quality grease the tensioner will last a long time.

I don't think that is the answer. If you hold the tentioner in your hand by the center, you will find that you can wiggle the "main" outside part. That means the bearing is warn out. (and the bearing is ready to fail) The one that came out of my '91 at 120,000, was clean and no real sign of lub on the outside of the bearing. As long as you have the belt assembly. apart, you should just replace the tentioners. "And the water pump !" (it's cheap insurance)

Bruce RED '91