I bought my 91 Legacy with 143K miles on it, I now have 147k. I have no idea if the previous owner replaced the timing belt. Is there any viable way of determining if the belt is original or not?

ask the previous owner. ask the previous shop that did maintenance on it.

 

pull the covers off and have a look at the belts. if they still have writing and look good, then they are likely fairly new. still a pain, because you'll never know unless someone tells you exactly when they were replaced. the left and right covers should be easy enough to remove just to have a peak. remove a couple small bolts and have a look.

 

i say replace them unless they look really good. i highly doubt the belts are original, it is very unlikely they would last that long (i'm sure someone will now post they drove 234,000 on an original belt). best to replace them if you're not sure. if it breaks you're definitely not going anywhere unless it's all downhill.

 

at 143,000 i would bet they weren't changed anytime recently. easily could have been a factor in the previous owner getting rid of the car. "ooh....70,000 miles is up again, let's get rid of it instead of paying someone 500 dollars to replace the belt on a car with all these miles." but there's no way to tell unless you can ask the person who did it or owned it.

One would hope that timing belt manufacturer/Subaru would put date of manufacture on it. I looked at my old belt and I can't find any obvious numbers that would provide that info. Too bad

<<One would hope that timing belt manufacturer/Subaru would put date of manufacture on it. >>

 

Why? what good would that do? belts are changed in miles, not time intervals. you can get a belt thats been on the shelf for the past 4 years and it will last as long as one just made. I have done dozens of timing belts, i have seen shreded ones and ones that look brand new. no way you can really tell just by "looking" at the belt. if in doubt, replace it. it will be the best $250 you can spend!

Obviously if it looks damaged, one should replace it. The real problem comes when they look good. My timing belt at 88K looked in good shape without a single crack or anything.

 

Given that belts are supposed to be replaced once every 105K = 5-9 year range, it can provide a very accurate idea. In the example in this thread, if the timing belt is original, it would probably have a date of 91 or earlier. I certainly hope that if I get my timing belt replaced today, no one would put one made in 99 or 2000 even if it has great shelf life.