Timing Belt Longevity And Risk

[BonzaiDuck]

My latest project with my old vehicle is explained in another current thread.

I bought the SUV when it had 95,000 miles on the odometer, and my experience with repair and replacement schedules was an interplay between ignorance and surprise -- but I've really been on top of things for the last 15 years -- approximately.

At 158,000 miles, my timing belt broke, and it was really a miracle that no engine damage occurred. Timing belt replacement is recommended every 60,000 miles, and we cannot believe the previous owner of the vehicle had swapped out the timing belt just before he sold it to me. If the previous owner had followed the owners' and shop manuals, the timing belt would've been swapped out at 60,000 miles, so I could imagine that the belt that broke might have had almost 100,000 miles of use.

I currently have about 17,000 miles remaining before the spec replacement mileage. But -- the previous belt broke in 2009. It has been now 15 years since then. Some online wisdom suggests that the rubber timing belt should be replaced every ten years.

Anyone have further insight about this? I am now toying with the idea to schedule a timing-belt replacement for next year or thereabouts. Or -- should I wait for another 17,000 miles?

 

[VirtualLarry]

rubber timing belt? recommending every 10 years replacement? and it's gone 17 years? Ye driving on a wing and a prayer.

 

[sdifox]

Take a look at the belt and see if there are cracks. I would say replace it. Along with the idler and tensioner. Usually sold as a kit. May as well do water pump at the same time.

 

[lxskllr]

I'm not familiar with timingbelts, but an inspection is sensible. In general, replacement schedules are set to occur well before failure is a possibility. IOW, you can extend them, sometimes significantly, with little risk of failure. If a company said replace at 60k, I'd push it to 100k. Your first timingbelt failure was probably the original, so it lasted 158k before failure. Time's hard on rubber, so give it a look.

 

[mindless1]

Both of the engines available in '95 appear to be non-interference (pistons won't hit valves) so it is unlikely that the timing belt breaking would cause damage, but yes it is due for a belt change and potentially the other related components and if the water pump is a lot more accessible in the process, might as well get that taken care of too.

It is time as well as mileage that degrades rubber belts, when talking about more than single-digit years. Once they dry rot, they wear out a lot faster. 17K more miles on it now, is more wear than 17K mi. when it was new. That does not mean I am certain it won't go another 17K mi. My crystal ball is wrong about 50% of the time. Either it will or it won't.

 

[jmagg]

Most timing belts take a fair amount of labor to simply observe, so if its interval is up, it makes sense to just replace regardless of how it looks.

 

[pcgeek11]

Most timing belts take a fair amount of labor to simply observe, so if its interval is up, it makes sense to just replace regardless of how it looks.

This.

If you dig into it far enough to look at the belt you may as well replace it while there along with anything else that is a wear item inside the timing cover.

That is another reason all of my vehicles have a timing chain.

2012 Tacoma and a 2010 Highlander. Both are 2.7L 4 cylinders.

 

[BonzaiDuck]

This.

If you dig into it far enough to look at the belt you may as well replace it while there along with anything else that is a wear item inside the timing cover.

That is another reason all of my vehicles have a timing chain.

2012 Tacoma and a 2010 Highlander. Both are 2.7L 4 cylinders.

Interesting point, especially since I was looking to Toyota for replacement vehicles.

My friend in Albuquerque has a 2001 Nissan Xterra which he'd purchased new. It currently has 122,000 on the odometer after 25 years. He just this last month or so replaced the timing belt -- for the first time! 25 years and 17,000 miles beyond the recommended replacement interval of 105,000.

I'll talk to the shop-owner/service-advisor when I get the car back for the other things of this last week's project. But with 17,000 miles still left on the belt-replacement interval, I might just wait until next spring -- or at least until January.

To my way of thinking, the previous Trooper timing belt had either run for just under 100,000 miles if replacement had been done by previous owner at 60,000 miles, or it lasted for 158,000 and was the original factory timing belt!

Someone mentioned or passed on information that the Trooper engine was a "non-interference" model, so with a low risk of engine damage if the belt breaks. But avoiding such an event is high priority.

Even so, the project to replace the belt should include -- as some have already mentioned -- the water pump, and some other parts. Last time it was done, I replaced the front mainseal and the cam seal as well.

Most normal people don't consume themselves with repair-history spreadsheets, factory shop manuals and other things. They avoid that by buying new vehicles. Alternatively, they buy a used vehicle, give it minimal service, and drive it until it costs them more than $1,000 in repair.

But I'm not normal.

 

[Torn Mind]

Inspect for cracks. If there is none and two other factors detail below are considered, you can probably use it until the mileage limit. IIRC you were in Cali, is it "mild California" or is this the desert?

Do you long distance drive or is this mostly short trips? The more long distance driving, the more necessary a swap earlier.

Is the engine bay full of aerosolized oil or has the valve cover gasket already been swapped?

 

[BonzaiDuck]

Inspect for cracks. If there is none and two other factors detail below are considered, you can probably use it until the mileage limit. IIRC you were in Cali, is it "mild California" or is this the desert?

Do you long distance drive or is this mostly short trips? The more long distance driving, the more necessary a swap earlier.

Is the engine bay full of aerosolized oil or has the valve cover gasket already been swapped?

Since the last belt broke in 2009, this vehicle has mostly been used for local trips. For a few years, I might have taken it up and down Mt. San Jacinto to visit or transport my now-departed brother who worked as a "resort chef" -- possibly once monthly. I replaced the valve cover gaskets in 2019, although I do not believe it was necessary -- I was pressured by a new repair shop I was "vetting" -- a trial-and-error problem for high-mileage owners of orphaned models. I might have consulted my spreadsheet at that time to find that the valve-cover gaskets had been replaced four years and 50,000 miles earlier. Why do I think that was premature to replace the valve-cover gaskets again? My spreadsheet provides me a wealth of history and information, but when I look at it for too long it makes me feel stupid for mistakes I have made.

My current repair shop, which does clean, professional and stellar work, was charged to find a very minor seep or leak which seemed to be coming from the pan-gasket. They steam-cleaned the underside of the engine, put dye in the oil and didn't really find a leak with the special glasses for the dye. My drop pan has been dry as a bone now for about three days . . . Either the Blue Devil has finally done its work, or somebody snugged a pan-gasket bolt and didn't tell me about it.

The engine compartment and its contents have been kept very clean for a long time. The water-pump has probably been kept in good shape for using the 16-oz bottle of lubricant additive and doing periodic flushes.

But especially after reviewing the spreadsheet, the last timing belt had lasted either 98,000 miles or 158,000 miles with a 60,000 mile replacement interval. I can find no indication through CARFAX that the original belt was replaced at 60,000, so it must've somehow run on the Trooper for 158,000. The original owner had been Enterprise, and they sold it before the timing-belt limit. The subsequent owner may have assumed too much about Enterprise maintenance, and I doubt that he had it done.

I'm going to control my paranoia if the belt still has 17,000 miles before the next recommended replacement, even if it's been a lapse of 15 years.

I can see that my repair shop's owner is eager to do the work, but even with that, he'll have to wait another year. He'll get some less expensive work from me in September.

Another reason I'm concluding that the SUV went 158,000 miles on the original timing belt before it broke: Enterprise Rental had first purchased the vehicle new, and held it for about 40,000 miles -- 20,000 prior to the timing-belt replacement milestone. They sold it to a San Bernardino dealership employee, who then sold it to me at 95,000 miles. Why do I think he had assumed nothing was needed because he bought it from a rental outfit? He just did. It's a normal assumption someone could make, even if knowledgeable about vehicles generally. What else? When he sold the car to me, the tires were practically bald. I would call that a "pattern of behavior".

So the Trooper had gone to 158,000 miles on the original timing belt! I myself didn't think to have it swapped out soon after buying the vehicle.