The Mystery of the Snapped Timing Belt Mystery
 

Er, so, I'm driving along the freeway with my buddy to get a new video card to replace the one which spontaneously broke while bitching about my phone which spontaneously broke when my timing belt spontaneously brokes.


Car: 2000 with a VVT motor, big valves, plenty of piston clearance. Put motor together say... 6,000 miles ago, went through it with a fine toothed comb. I put on a new tensioner and idler...

But I think my timing belt may have been generic. Says "MADE IN USA" along with TX179 and C40088 on it. There are no worn edges or any evidence of wear, it looks pretty new to my eye.

I DO have heavy valve springs in the car, nothing crazy, lighter than many of the typical performance springs you see.

The cams turn over about like normal - intake slightly harder than exhaust. Bottom end is fine, oil came out very clean, filter looks fine.

There IS one issue though - I was pretty low on oil, some leak must have gotten worse - oil pan doesn't look great and #3 was burning a little oil due to a small score in the wall. Anyway, I was a hair over 2 qts in the motor, with another half in the FM Twincooler. That is certainly on the low side, and odd since I had checked it within the last 1k miles.

Oil temps were ~220, ten degrees up from where they had been earlier that morning, and it was a 100 degree day out so this isn't unreasonable. Water temps were ~190-200 - so typical hot weather running.

Do you guys thing the head could have been a little oil starved, and cams got hard to turn? It was a little drier up there than one would expect, but far from dry. Everything looks ok. The cam belt tensioner is maybe twice as hard to turn as the idler, but far from HARD to turn - easily a one finger job.

I guess my question is - do I put it back together with a mazda belt, keep it full of oil and count my blessings, or is there something else to check?

http://abefm.smugmug.com/Miata/Quest..._150048-X3.jpg

http://abefm.smugmug.com/Miata/Quest..._150120-X3.jpg

http://abefm.smugmug.com/Miata/Quest..._150131-X3.jpg

http://abefm.smugmug.com/Miata/Quest..._150155-X3.jpg

Higher Res and Additional Views at http://abefm.smugmug.com/Miata/Quest...roke/i-L7fxZJr

I had one snap the exact same way. I actually ran my old belt to get me through, and it lasted another 30k.

I would say fuck it, count your blessings, and run the piss out of it, (with a gates blue, soooo worth the small $ increase)

Looky what's over in the classifieds: https://www.miataturbo.net/miata-par...pullies-80573/

Great belt, and it may not hurt to make sure your pulleys are 100%

(no affiliation btw)

$60 shipped on Amazon, AND I've got new pullies on it. But I guess the Gates belt is the way to go.

I've never had a problem with the OE belts, that's for sure. I should have reused my old one myself.

So why does the tensioner pulley spin differently than the idler pulley? Were those an economy brand also? Gates does make good pulleys.

Definitively Mazda. Don't know why they are different. Kinda afraid to get caught up doubting everything.

No, I understand. I was just thinking of the comment you made out them spinning somewhat differently, and I just can't remember them being different when I did mine. Maybe someone else will comment on that for some balance.

I have nothing to add other than I like your banjo fitting setup for what I assume is the turbo coolant supply line.

Yeah, clever use of the old water port.

Are your cam pulleys exposed? Any damage or nicks on any of the pulley teeth? That's a failure we (jesel) see when the belt load is too much, typically when the engine goes kablewey, or running too many accessories,off the cam drive. Not a crimp or de lamination failure.

Besides the broke belt pic, the rest look normal.

The font style (but not color), numerical codes, bar code layout look like our gates belts. The jacket (fabric on the teeth) looks to be the same too. But I have no experience with other belt manufacturers...they all might look that way.