Potentially snapped Timing Belt

I've only ever had one timing chain fail (just too much slack - it still ran) with a conventional cam/pushrod/overhead valve. The length, sliders, and tensioners plaque the overhead cam versions especially in variable valve timing version (looking at you, Ford). They do have the benefit of external water pumps but are also much harder to service than a belt.

I'm a big fan of less maintenance, but changing a tensioner and chain system is way more work than a belt every 100k.

I also believe that a well designed chain system will outlast a vehicle, but manufacturers would never approve the cost increase. Belts and tensioners are all considered wear items - so no warranty work needed.

 

I'm not saying Totota's chain systems are perfect, but I've never heard of one failing -- even on vehicles with hundreds of thousands of miles.

 

Haha yeah, you're definitely not wrong. Previous owner said that it needed to be changed at 230K miles, but still dumb of me not to do it sooner. Live and learn, this just happens to be a lesson learned the hard way. Well, jury is still out on how bad it'll be...

 

I had 100k less on my truck and it sat in the driveway until I got it to the shop to get it replaced. It was 5 years past do and 25k miles. I had to drive 200 miles to get it home and I was paranoid the whole time. I have read several stories of people pushing this limit.

I had a timing belt break on a honda civicmany years ago. I was pulling a trailer at the time. I had the belt replaced a year or two earlier, and it died after 40k. There was no damage and I put another 50k on that car.

 

Similar here. I got a 2000 Tundra at 155k miles, and not any records of a timing belt. I drove it very gingerly and less than 250 miles until I could get it in the shop. I'm not sure if it had been done, because the belt they took off looked really good... I figured it was either way overdue on time/miles, or if it had been timely changed, it was due very soon, anyway, for another belt. But this service, along with the other usual items (water pump, thermostat, etc.) identified a malfunctioning thermostat housing that had some issues and needed replacement anyway. So digging in there identified problematic issues.

I got a 2002 with 240k miles that had a sticker on the engine showing it had been serviced 9 years and 70k miles ago. I had the service done and put only less than 500 gingerly driven miles on it until the service could be done. I figured I probably could push it a bit, but was wanting to get it done for sure and anything else in the region since I have no records of anything else in the region having been replaced; so I was running on 20 year old water pump, thermostat, serpentine belt, etc. Time to just get in there and do it all. And oddly, the mitsubishi timing belt was pretty stretched and a lot more floppy and limp than the timing belt we took out of the 2000, which might have had twice the mileage on it as the mitsubishi belt. It was a mitsubishi and not an aisin, so I think the mitubushi is lower quality.

 

Iirc the Aisin TB Kit comes with a Mitsuboshi Belt.

 

That's impressive. I remember my dad popping the hood on his 1971 Ford Custom 500 when it was super hot out, or we were stuck in traffic. He always said it would help dissipate heat to have the hood cracked open.

 

Not to mention chains can make the engine have all sorts of noises you don't hear with a belt.

 

That's interesting. I still have my old belts, so I'll look to see what brand they are stamped with if it's legible.

 

Here’s some photos of the aisin kit I’m going to install this summer from rock auto.

All parts are made in JAPAN

 

Well, I kept my belts.

The one from my 2000 Tundra has unknown miles, and could theoretically be 155k. No records of it having been done. It's in better condition, and slightly more rigid and less stretched. It's possible it was changed at some point so may have less than 65k miles. Unknown. If there was a brand name it's worn off. No brand name visible, but a series of numbers is visible.




The one from my 2002 Tundra, based on the engine tag, had 75k miles and 9 years on it if I believe the Mitsub0shi tag. The belt is Mitsub0shi, so it is consistent with the tag. Of the two, it's more stretched and feels thinner.

I was previously wrong, it' not the more common Mitsubishi. My oversight. It's Mitsub0shi. I was so focused on reading the actual date and mileage, now almost impossible to read, that I did not look more carefully at the manufacturer. I used a big magnifying glass to get the date (2012) and mileage (170k)...

 

Looks like mitsuboshi CD298 to me in that second picture

 

I purchased 3 belts, all installed already this year. Unfortunately I don't know who made them. I bought them directly from Toyota.com and their part numbers are 1356809070. This fit both my Tundras and 4Runner. Looking around the web, it's not clear who makes these OEM parts and apparently could be Aisin, Mitsuboshi, or Gates... A bit confusing. All Toyota states is that it's an OEM part.

 

Mitsuboshi is quality which is why Toy uses them. Gates makes a nice HD Serpentine Belt.

 

So sis the jury come back with a decision?

 

This is the belt I took off at 228,000 miles. I found no evidence that it had ever been changed

 

Looks to be good for another 228k

 

Looks brand new.

 

Well, called the shop yesterday and they're 90% certain that it will be just fine. They mentioned that they've seen plenty of engines totally messed up from this kinda thing but that there was nothing they saw that would lead them to believe my engine was damaged. I was told once they have the engine put back together and running, they'll know for sure if it's good or not, but so far so good.

I was so happy it almost brought tears to my eyes haha but I should know more today! Thanks for sticking around on the journey

 

Get a powerball ticket before your luck runs out!!

 

Have you asked what brand of belt they are going to put on it? We've had some members go with an aftermarket belt only to have it jump or break.

 

Everyone deserves a break now and again! Sometimes it feels too few and far in between. I wholeheartedly hope it works out for you.

 

I did not ask but that sounds like a good idea. Thanks!

 

Water pump, tensioner, idler pulleys, cam seals, potentially fan bracket, the works while you have it apart. Good time for a radiator replacement if it's never been done, or at least a flush and fill.

 

I am glad it's ok!

 

Well said, indeed… couldn’t have said it better. Here’s for good news

 

Not totally outta the woods yet, but should know soon! Will keep ya posted

 

Congrats OP, and I would have them do this while they have it opened up. Use only quality new OEM parts. It'll cost ~$1300 or so.

 

I think 4.7L is a non interference engine. That means that at no time do the intake or exhaust valves open far enough for the piston to hit them at top dead center. Should the timing belt break and the cams stop turning or otherwise lose cam timing, there should be no damage to valves, cams, or the rotating assembly. That is a great thing in this instance and Toyota designed the engine this way as a fail safe.

An interference engine will have valve opening events with enough lift that timing must be maintained or valve to piston contact is likely. On the plus side those larger opening events flow more air and make more power.

Toyota opted for a safer valve opening strategy at the expense of making more power.