Timing Belt

[murphsubaru]

What are the chances of a timing belt breaking???? I have a 99 Forester with 98,000 miles, according too Subaru the belt should be replaced at 105,000 miles. Should I replace it at 105,000 or chance it??? I believe this is an interferance engine.

[Manarius]

It's got 98k miles on it, I'd replace it now. You don't want it to break on you...that basically destroys the bottom of the engine.

[rweddy]

It's got 98k miles on it, I'd replace it now. You don't want it to break on you...that basically destroys the bottom of the engine.

Love the avitar Manaruis, but it will actually damage the top end, piston hits valves.

[Manarius]

Love the avitar Manaruis, but it will actually damage the top end, piston hits valves.

But, you'd need to replace the bottom end too - if you get a dent on the piston head....

[rweddy]

But, you'd need to replace the bottom end too - if you get a dent on the piston head....

But this happens less than 5% of the time, generally if you snap a timing belt you only do valve damage. You can do piston damage but it is very rare.

[Manarius]

But this happens less than 5% of the time, generally if you snap a timing belt you only do valve damage. You can do piston damage but it is very rare.

Either way, if the timing belt breaks, the engine needs to come out.

[porcupine73]

Yah I'd just do it as soon as convenient, before 105k of course, sure it could last a lot longer than that but if it does break it won't be a cheap fix. There is a common list of other things that should at least be looked at while the timing belt is off and indeed probably just replaced like the cam seals, crank seal (on the oil pump), water pump, the geared idler pulley and inspect the other idlers. I just go with a new tensioner each time that way I don't have to mess with pressing the rod back in and plus I know I've got a good one in there that way.

[hohieu]

I had just over 105K miles on the same car before replacing the t-belt last summer. The old one looked fine, but you usually can't tell much by looking at a t-belt.

 

Remember to do all the other stuff while you're in there.

 

Freewheeling bearings indicate a shortage of grease -- new idlers have a bit of drag. A these idler pulleys fail because they eventually run out of grease, but they can be regreased quite easily by prying off the seals which are rubber-coated metal seals. Be careful not to bend or deform them as you gently pry around the outer circumference with a small standard screwdriver. Apply only a light coating of Lithium or lithium complex grease to the ball bearings inside and reinstall the seal with an appropriately sized socket (overgreasing can cause the seals to rupture). If you're wearing latex gloves, you can use your thumbnail to work the lip of the inside circumference of the seal into place without risk of damaging them. It's a very simple job. And you could do all 4 idlers, including the tensioner.

[nipper]

Usually what happens is not that they break, is that they jump a tooth. I would wait till 105,000 miles, unless you have some need to do it now. If you push it beyond 105,000, way beyond then it may break, the tensioner can fail, etc.

Ive always had the luck of a timing belt going 2000 miles past the change date.

 

nipper

[kimokalihi]

Why chance it though? You know it's going to break right when you need the car the most(mine broke while I was passing 2 vehicles, one of which was a truck pulling a big horse trailer)or in the middle of nowhere in the rain.

 

Then you'll have to tow $$$ it and pay a ton of money for someone to fix the engine for you, assuming you don't know how to do it yourself. Or you can do it yourself and it will still be a pain in the rump roast and you'll hate your life for making the stupid mistake.

 

Luckily, my engine is non-interference and my step dad has a big Dodge cummins 2500 with a trailer fit to haul a large bulldozer. I just picked up the belt and slapped it on there and it's run flawlessly for the past 8 months. I didn't know when the belt was last replaced or if it had ever been because it broke the 2nd day I had the car.

 

But the choice is yours.

[NoahDL88]

Either way, if the timing belt breaks, the engine needs to come out.

 

Hate to poop on your popcicle, but the engine has plugs that allow the pistons to be pulled without pulling the motor, and the body has holes that allow the head bolts to come out for the same reason. "amatures" tend to pull more than they need to, which makes the final job easier, but takes much more time, professionals pull as little as possible, and are only slightly inconvienienced by reparing heads and possibly pistons in car.

 

And really the piston isn't really bottom end is it? i mean, theres no bearings on it are there?

[avk]

It indeed seems physically possible to remove pistons with engine in place, but it may not be a good practice for several reasons, and I'd be surprised it it was widespread.

[rlsimpso]

Could you shed some light on the holes in the body for pulling the heads? I don't recall seeing anything mentioned in any of the manuals I have.

 

I think my head gaskets may be going (pulling the spark plugs tomorrow) and am considering replacing them myself. It would save me a lot of head ache if I could be done without removing the engine.

 

Although, if you have close to 100K miles, wouldn't it be a good idea to put in a new clutch (assuming manual trans) and replace the rear main seal? If you can change the clutch without pulling the engine, I will be impressed.