29 replies to this topic

[Wallowa]

Hey,

 

Thanks for all the input and it is appreciated.  My conundrum is that my '05 Tundra only has only 41+K miles but is obviously 13 years old.  The "time or distance" issue is not a simple one to resolve.  No telling the condition of any component buried inside a motor; odd the serpentine exposed belt has no such "replace by" date and visually inspecting one is again a crap shoot.

 

Just had a 'recall' on our '10 Subaru Outback [wiper motor cover]; same same on replacing the timing belt @ 105K. 

 

I would have gotten a 'life time' chain timing belt in the 6 cyl if I had know about "interference motor"... I asked what a new 4 cyl motor would cost if I lunched mine..$5K.  Bet a new 4.7 in Tundra is a hell of a lot more expensive.

 

I will go on mileage with the Tundra, but will chicken out about 60K and pony up the bucks...new pulley, water pump and belt will be around $1K...

 

My personal opinion is this is a poor way to design a motor.

 

Phil

Edited by Wallowa, 03 October 2018 - 12:50 AM.

[ntsqd]

I had a '72 Pinto Wagon when I was young and it ate timing belts due to the crank pulley being worn and too expensive for me to replace at the time. I got so that I could do the whole job on the side of the road in about 15 minutes. Could buy a lot of belts for the $100 that I was quoted for that pulley!

 

That said, if you're already in there for some other reason and given the details mentioned above I wouldn't hesitate to replace it.

[wuck]

Funny thing... we used to have a 1998 Toyota Avalon.  In the USA, it was 100k miles between timing belt changes.  In Canada, 100k km.  Same car.  Mazda was the same way.  

 

Maybe there was an ex-NASA employee was involved in the service manual??

[Vic Harder]

LOL!! 

[carld]

If Toyota specifies 90k then the failure probably at 90k is probably less than 1%. You are probably good for 200k miles. When the water pump or tensioner look like a problem then do the timing belt.

[Vic Harder]

Carld, I respectfully disagree.  The cost of NOT doing the timing belt is high.  The cost of the belt/labor is minimal in comparison. 

[carld]

Ya on my last Tundra I did the 90k maintainance at 180k then another one at 260k.  You are right the concequence is dire but I'm an enganier "at least I think thats the way I think you spell it" and if the company says it might fail at 90k miles the probability is vary vary low, better than a half life and maybe more like 3 to 6 times.  So I'm not saying that you should do it, I'm just saying don't worry too much.  You are more likely to have a water pump or surpentine belt issue first. 

[ntsqd]

I know of a specific engineering case that might offer some insight into Toyota thinking. First gen MR2 engine, a 4A-GE, had a Toyota set redline of 7800 RPM. Len Frank (for those of you who remember his by-line) asked a Toyota Engineer about that when the car and engine were first introduced, how long could the engine be expected to live if it could be spun up that fast. The answer was 100k miles, at least, when run at 7800. Imagine running an engine at 7800 RPM for 100k miles!

However, spun up to 8200 RPM and it's life span was about 20 minutes. Consequently the ECU soft limited at 7800 RPM (ask me how I know this) and only by deliberately down-shifting at speed could you get it past that. I don't think Len put this in his article on the car, but he told many of his friends about it. I was lucky enough to have briefly known him.

 

So, I wouldn't call the 90k service life a hard and fast rule, it has some tolerance. But I wouldn't make that tolerance too wide, Say 75kM to 110kM would be my own rule.

[klahanie]

>9,000K, 200K, >180K, 270-540K.  Gee, pity the poor lay person faced with those variations

 

Perhaps Toyota simply chose 90K as an easy number for their dealer service depts to work with and one that they calculate will generate income from the greatest number of customers.

[ottorogers]

Definitely change the belt no matter the milage, these belts can deteriorate, I would never take the chance, because like you said, if the belt breaks your engine is finished (potentially), sure glad the new Tundra's have a chain, my old 4Runner had a belt (4.7 V-8), and when I did change the belt at 100,000 miles I changed both idler bearings and the water pump, cost was about $500 and worth it for peace of mind