This is a dumb question but I reflected on it a bit. I was about to have the timing belt on my Subaru Forester replaced (since it has been since 2004 and has 56,000 miles) and the dealer said the belt looked fine and did not require attention. It is old and I will get it replaced anyway.

I wonder if manufacturers understate at times the timing belt change intervals.

I had an Alfa Romeo 164 that needed its belt replaced every 30K or 4 years.

I had one car whose timing belt broke. It was a Rover 200 coupe. It stalled suddenly as I exited off the motorway and I thought it ran out of gas. Cranked but no fire.

It was a 1993 model and this happened in 2013. Had 102,000KM or around 60K miles.

Therefore, the timing belt lasted 20 years!

 

there's several different factors in what makes a belt break.


time, weather, contaminates, rubber compounds, etc.


when in doubt, change it out!

 

All Forrester engines are interference engines. If the timing belt breaks you are looking at major engine damage.

10 years its time to replace it.

 

No one can say for sure. It's just dumb luck. There are stories from both sides all over the net.

 

replace the belt, Whitebear Subaru will do it for under $500 but that does not include the tensioner or idler pulleys. I just did my 2003 Legacy at 62K and it immediately cleared up all of the valve train noise. When I talked to my service advisor he said if it is 10 years old regardless of mileage, change it. The rubber deteriorates over time and you do NOT want to be replacing valves and or pistons.

to answer your question, YES they understate the replacement conditions as it would be a nightmare if they said the belt was good for 105K and there were a lot of failures before then

 

I would follow whatever the manufacturer says to change it. Manufacturers determine a mean time between failure from testing and previous history. This doesn't guarantee it will not break before then but you would be pretty damn unlucky if it did.

 

Yes, I think 10 years is enough regardless of mileage. The SOHC engines, I think, are non-interference. The DOHC engines are interference.

I went to Bloomington Acura Subaru. They said not needed so I will go elsewhere. I have not had a good experience with this dealer so I might as well.

 

^if you go to White Bear Subaru (HWY 61 north of 36) ask for Joshua and he will get you squared away. Adding a tensioner and the pulley/idlers will add about 250 to300 onto the job. My idler was shot and leaking when they did my belt.

 

Hard to imagine any business not wanting money?

 

^that dealer he mentions really sucks a donkey nut along with Brooklyn Park Acura. that dealer wants to repair the engine AFTER the belt snaps lol

 

Ferrari recommends changing their t-belt every 10k. All their engines are interface.

 

Most gas engines I have seen are 80-100k miles, or 8 years. I have seen some lower and vw diesels were 60k/5yrs. Definitely don't want to wait for breakage as repair costs are much higher on interference engines, and of course there's the inconvenience factor of the breakdown/tow. But it does pay to shop around. I know we are the lowest in our area for acura/honda t-belt replacement.

 

Just remember Age is FAR worse for the rubber belt than miles. I would feel more comfortable driving a vehicle that was 2 years old and 200k miles on the original belt than a vehicle that was 10 years old and 2k miles.

 

I hate that place. The service department sucks, the sales department sucks, the location sucks, etc... The last time I went there, they recommended I change the power steering fluid...which I changed literally the day before I took it in. I asked them if they even looked in the fluid reservoir or if they just assumed.

Unfortunately I live too far away from Bloomington Acura to make it worthwhile to go there instead.

 

I disagree, I would take the opposite. Modern rubber polymers in TB's are pretty amazing for aging and their resiliency, but the running of the engine causes bending and stressing of the timing belt fibers put more wear on the belt than aging.

 

It will break when you hit veetak.

 

the only dealer I recommended was Whitebear Acura Subaru

 

Timing belts very rarely snap but instead one of the teeth will usually break off, causing the timing to slip and bad things to happen.

As far as intervals go, older Hyundais that used belts had a 60k interval that I followed religiously. People refused to take it seriously and sometimes it worked out okay and other times it came around and bit them in the ass. I know a guy who went 78K on his original belt while another who joined the forum just to say the 60K was just a rip-off to make dealers rich had his slip less than a week later and came back eating major crow.

When in doubt, change it!

 

I would also agree that use is the determining factor for change interval. Heat and other environmental contaminants are the harshest factors for belt compounds and, as noted above, today's compounds are quite robust. If you're not using the vehicle much (so, low mileage), the belt is not seeing these environmental influences.

However, with use, not only does the belt experience more environmental influence but the mechanical factors go up significantly. It's not just the mechanical properties of the belt construction at work here. It is also all the components the belt touches. The bearings in each of these devices wear and the tensioner spring becomes weak so the belt walks, bounces, and slips more.

As far as determining replacement interval, there is software that allows the designer to plug in the pulley diameters, distances, loads and rpm. The software then calculates the necessary spring/belt tension required for tensioner system and the predicted life (in operating hours) of the belt. You normally then apply the belt service requirement within some other regular service interval. In the case of an auto tensioner system, it's life is often used to determine when the belt should be changed. Meaning, the tensioner life is less than the belt life so as long as the tensioner is being changed, a belt change is recommended.

 

when in doubt; change it out!

 

That's not too far for me but still a hike, I'm in Plymouth.

 

^ Remember to ask for Joshua, he is the Subaru guy. Tell him that I sent you over (see your PM)