Dropped my A/C belt. Is it the crank pulley? - Page 3 - Subaru Outback - Subaru Outback Forums
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post #21 of 29 (permalink) Old 11-07-2009, 07:55 PM
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I did some searching of other forums regarding crank pulley deterioration. According to some it is rare, yet I found enough postings about failures that I'll be watching it more closely. I'm hoping the painted line will be a reliable early warning method.

This thread is about a failure and has a photo of a "very failed" pulley:


Of particular note is the posters reference to the belts coming loose.

There are lots of threads here and in other Subaru forums about replacing the pulley (whether due to failure or changing it for other reasons).

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post #22 of 29 (permalink) Old 11-08-2009, 07:41 AM
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I think the intent of the rubber damper in the pulley (aka "harmonic dampener"?) is to minimize how much of the engine pulses (each cylinder firing produces a pulse of power) are transmitted to other engine components like the power steering pump, ac compressor, alternator, etc., as well as to the car as a whole.

This is to make the running engine power delivery "smooth".

Extrapolating, this might also--

--spare the serpentine belt and any other belts from being repeatedly pulsed/stretched, giving longer belt life.

--keep the pulley mounted on the crankshaft with less extensive mounting hardware (single bolt vs a splined shaft/pulley). (If that bolt ever comes loose, you will get a pounding racket that will make your car sound like a helicopter. Happened to my wife's Impreza. It will scare the **** out of you when it happens while driving.)

It's there for a reason. It if wasn't needed, would Subaru have spent the $$ to put one in? Unless you are an engine system designer/engineer, why would you think you could simply eliminate such a feature? Just because some company makes a part with the hope of separating you from some of your money?

Any time you put in a significantly cheaper part, you are giving up something else (performance wise) in the bargain. Just be sure you have thought thru the effects of what you are going to do, and are willing to make the trade and live with the results.

Find and support a trustworthy, experienced, competent, certified mechanic. Then when you are considering doing something like this, you have someone you can have a five minute conversation with and get a deeper understanding of the likely effects. It's still your decision and your car and your $$$$, but at least you will be making informed decisions. This philosophy has proven invaluable to me over the years.

(This board is filled with many very competent participants, offering excellent advice, but there is no guarantee that they are all right all of the time, dispensing remote advice. Nothing better than competent boots on the ground, listening to you and your car.)

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post #23 of 29 (permalink) Old 11-08-2009, 12:25 PM Thread Starter
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Thanks guys.... time to start patrolling the junk yards with my trusty breaker bar.

my car has 112,000 kms's on it... about 70,000 miles.

Not something that I would like to see happen that early.

I wonder if the turbo crank pulley is the same as the 2.5i? I'll have to call the stealership I guess...


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post #24 of 29 (permalink) Old 11-08-2009, 05:04 PM
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Originally posted by plain OM
. . . .
I had intended to mark the pulley on my 07 the same way, but didn't have a chance -- will be doing it tomorrow morning (Sunday) and taking it out for a ride. If there isn't supposed to be any rotational movement between the two parts (and my test confirms it), then I wonder if this might be a way to monitor for impending failure of the rubber damper.

. . . .
Just a quick follow-up. I painted a line on the pulley today and was out with the car -- no sign of movement between the two parts. So, the line stays on and I'll be glancing at it whenever the hood is up.


I checked on www.opposedforces.com and found that the part number(s) for the crank pulley is the same for both the NA an turbo. There are two numbers, depending on build date.

Here's the NA page: http://opposedforces.com/parts/legac...llustration_2/

and here's the turbo:
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post #25 of 29 (permalink) Old 11-08-2009, 09:22 PM
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FWIW, i've got 2 Subaru's (an Outback and Impreza), both have L.W Crank Pulleys.

The one on the Outback has been on for ~60k km, that car also has a L.W Flywheel, Delta Cams, handling upgrades, exhaust, intake etc etc.
No problems with excessive vibration, stuff exploding or parts falling off.

The one on the Impreza has been on for ~50k km, basically stock except for handling upgrades and an intake.
Again, no problems. This car just had the timing belt, idlers and tensioner replaced and the mechanic (I couldn't be bothered changing the belt on a quad cam car...) said all was good.

Stuff goes here.
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post #26 of 29 (permalink) Old 11-09-2009, 02:55 PM Thread Starter
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I'm going to go with the OEM option. Can get one new from a shop for $150.

Love the lightened idea, but wonder why the pulley wasn't lightened in the first place...

Maybe I'm just missing out...

I"ll keep the post going if there are any more issues.

For removal and replacement, I think it's emergency brake on, and transmission in first gear? I"m going to need to get a 22mm socket in 1/2 drive.

Thanks again for everyone's help.

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post #27 of 29 (permalink) Old 11-09-2009, 04:34 PM
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If you have to buy a 22mm socket, try to get a six-sided one instead of a 12-sided one ... it's less likely to round the corners on the crank bolt head. When I did it, I ended up getting an impact wrench socket set from Harbor Freight ... the set cost less than a single socket at other places and has worked just fine for me.

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post #28 of 29 (permalink) Old 11-14-2009, 01:07 PM
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I just want to back up bobbyjimmy on the use of LCP. I have a Perrin LCP that I put on my 99. Then I got a 2005 XT and took the pulley off the 99 and put the pulley on the XT. It runs just fine-no vibration at all. It does help a tiny bit in faster shifting since the engine RPM drops a bit faster when you are changing gears (I have a manual trans). I paid about $50 on eBay for a brand new one. That was a lucky bid.
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post #29 of 29 (permalink) Old 12-07-2009, 11:18 AM
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Just had the same thing happen on my sons 04 with about 80,000 miles on it. It had shredded the AC belt and PS belt wasn’t in very good shape either. I thought something had seized. After checking all of the pulleys and not finding any obvious seized parts, we replaced both belts and started it up. There were no problems and no noise. When I told him to give it some gas, the AC belt jumped off. So I took off both of the belts and grabbed the crank pulley and the pulley part came off in my hand leaving a smooth nub bolted to the end of the crank. We pulled off what was left of the harmonic balancer and have a new one on order. When I spoke to neighbor who I borrowed the cheater bar from he mentioned that he had seen this before and that sometimes the whole thing flies off and makes a mess.
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