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Notes of Timing Belt


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10 replies to this topic

#1 jman11

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Posted 14 December 2005 - 10:38 AM

Just a couple of notes about my recent timing belt change on a 2000 RS Impreza. To start things, while trying to figure out the tooth count, I found a really useful little pdf file. It has the numbers for the replacement parts for, it seems, every subaru since 1990. It's an endwrench article and here it is:
http://endwrench.com...enanceparts.pdf

First, teeth counts: the book is wrong, every book I have heard about is wrong. It is NOT 40.5/44 tooth on the two sides. It is three more: 43.5/47, the marks on the timing belt are correct. I'm sure there are some engines out there that work with this belt, but the 2000 2.5L SOHC from an Impreza does not seem to be one of them. What doesn't help is that the Subaru shop manual states the lower, incorrect, figure. Everyone also seems to be able to use the lower, incorrect figure.

Second, how to get the timing belt back on. The general consensus seems to be to remove just one pulley, the cogged one sitting right next to the water pump. You should definitely remove this one to get the belt off, it gives you heaps of slack and makes it real easy. It's a pain to get back on, though. It's easier to take of the other, lower pulley as well. Then put the belt on and then the cogged pulley, lastly put the other lower pulley back on. This gives you just a little more slack, when you are fiddling round to try get the cogged one in. The little bit of slack you gain makes it so much easier, it's then really simple to put the other pulley back in. This length of belt is now the longest possible and really asy to deflect and put the last pulley back on.

Third, make sure you get that tension belt fully compressed and don't put something that will flex in it. I started with something that flexed a little (only about 2-3mm, but enough). This made it almost impossible to get the belt back on. I used the largest (it was SAE) hex key I could fit in. If it's thick enough it won't flex and will work. The tiny amount of flex meant the belt wouldn't go back on.

Fourth, make sure you move the rubber seal from the old water pump to the new, if you change it.

Fifth, make sure you take of the camshaft sprocket before you take off the timing belt.

The last two allowed me to perfect the timing belt replacement. I ended up doing it 3 times in a week. The big thing I want to emphasize is that you can ignore the teeth counts. Just look at the belt and line it up with the sprockets. It should come close to the marks on the engine, but might be off by a cog or a half.

#2 sid_vicious

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Posted 14 December 2005 - 03:04 PM

To start things, while trying to figure out the tooth count, I found a really useful little pdf file. It has the numbers for the replacement parts for, it seems, every subaru since 1990. It's an endwrench article and here it is:
http://endwrench.com...enanceparts.pdf


That file will be a sweet reference, thanks!

Andrew

#3 svxpert

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Posted 14 December 2005 - 03:40 PM

<<The last two allowed me to perfect the timing belt replacement. I ended up doing it 3 times in a week. The big thing I want to emphasize is that you can ignore the teeth counts. Just look at the belt and line it up with the sprockets. It should come close to the marks on the engine, but might be off by a cog or a half.>>


nice post. "teeth counts" has been a regular topic here lately. i have replaced many subaru timing belts and have never once sat there and counted teeth. just line up the cams and the belt properly and you'll be fine.

#4 avk

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Posted 14 December 2005 - 04:08 PM

The lower numbers are for the original, cylindrical tensioner design.

#5 97OBW

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Posted 15 December 2005 - 01:25 PM

what advantage does a belt have over the chain? less friction?

#6 frag

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Posted 15 December 2005 - 02:16 PM

what advantage does a belt have over the chain? less friction?


I would guess more silent and no need to lubricate.

#7 97OBW

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Posted 15 December 2005 - 05:48 PM

my honda is a much quiter car and the owners manual says nothing about maintaing the timing chain

#8 Johngenx

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Posted 15 December 2005 - 06:21 PM

Chains wear out, just like belts. However, it's usually at a much higher mileage than a belt. You can really prolong the life of your chain if you change your oil and filter often and use synthetic oil. The double-row chain on my Mercedes lasts at least twice as long as the belt system on the Forester and costs half as much to change once it does need replacing. I wish more makes would get off the belts...

#9 jman11

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Posted 16 December 2005 - 09:07 AM

Could it be because of the boxer engine. When I think of timing chains, I think of them being fairly short. So for an inline, or V# engine. you can then have a fairly short chain. Whereas for a boxer there is no hope for it to be short. It's going to have to be fairly long and thus heavy.

Another thing could be the orientation. Once again when I think of timing chains I think of them running mostly up-down. This means that gravity won't cause it to sag as much. Whereas with the boxer there has to be a lot of lateral length of chain. With a heavy chain, rather than a light belt, it might sag too much.

#10 friendly_jacek

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Posted 16 December 2005 - 12:05 PM

No, it's not boxer thing, H6 has a chain.
The manufacturers went to belts sometime in 70-80's due to less stretch in belts vs chains. Supposedly queiter too, but a minor thing.
The move back to chains in the 90-00's is to prolong service intervals and increase reliability.
Subaru went back to chain in H6 for mere space savings.

#11 svxpert

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Posted 16 December 2005 - 03:41 PM

<<Subaru went back to chain in H6 for mere space savings.>>

went back? when did they ever have a chain before the H-6?




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