Alternator Decoupler Pulleys - Toyota Nation Forum : Toyota Car and Truck Forums
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post #1 of 6 Old 01-02-2015, 02:34 AM Thread Starter
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Alternator Decoupler Pulleys

I had an alternator decoupler pulley (ADP) failure, a product I had never heard of until today. I did not locate a thread addressing these pulleys; so, I thought I'd start one to inform/help others. Most of the info below is from the Gates/Napa website. I found their website and youtube videos very informative.

There are currently two types of ADP pulleys: Alternator Decoupler (OAD) Pulleys and One-Way Clutch (OWC) Pulleys. Toyota products use the OAD type.

Essentially, these pulleys have a clutch-type mechanism inside the pulley that allows the pulley to free-spin when de-accelerating. It's suppose to smooth out engine vibration and "improve the performance and efficiency of car and light truck engines." Sounds hokey to me; it's just another auto part susceptible to failure and a profit maker for the stealerships, but that's just my .

It's fairly easy to identify ADP pulleys. The end of the pulley will have a cap or similar cover to protect the innards. Under the cap, it will look like the one on the right:




Diagnosing ADP pulley Failure
--If you hear a buzzing noise immediately following engine shutdown, the bearings in the pulley have failed and it will need to be replaced. In this situation, if you turn the pulley by hand, you may feel grinding or roughness.

--When you hold the alternator still and the pulley spins in both directions, it should be replaced. The pulley should spin freely in only one direction and engage the alternator in the other.

--If the pulley won't spin freely in either direction you’ll need to replace it. You'll experience increased tensioner movement or belt slap when the engine is operating with a seized pulley. [The tensioner may have to be replaced, for a seized bearing puts excessive strain on the tensioner.]

--There are metal shavings inside the pulley.

My pulley failed the second and forth test. When I removed the cap, the innards were full of a fine rusty dust.

Removing the Pulley
Needless to say, removing these special pulleys require the purchase of new tools. They range in price from $40-$120.

When to Replace?
As preventive maintenance replace the pulley when rebuilding the alternator and/or when replacing the serpentine belt.

Some Toyota models with these pulleys:
4Runner 2.7L, 4.0L
Avalon, Camry, Highlander, RAV4, Sienna, Venza 3.5
Camry 2.5
Celica, Corolla, Matrix 1.8
Lexus ES350, GS350, IS250, RX350 2.5 & 3.5
Scion XB, XD 2.4
Tacoma 2.7
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post #2 of 6 Old 07-28-2017, 03:28 PM
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I was able to change my alternator decoupler pulley with the special tools. It was completely seized up. Thanks for the information. My neighbors and friends have not heard of an ADP yet.
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post #3 of 6 Old 02-18-2018, 09:49 AM
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I have a 2008 Matrix that was making a new sound in the serpentine belt area. I checked all of the pulleys using a screw driver, a method that I saw on You Tube that used a long screw driver with its tip placed close to the bearing and the handle was placed in the person's ear .The sounds of a particular bearing would be transmitted through the screw driver to the ear. All of the bearings sounded similar. The only unusual thing was that the tensioner was bouncing up and down by about an 1/8 of an inch.

I replaced the tensioner with a new one which had no effect on the sounds or its bouncing.

I read your post above and thought that you had solved my problem-- the decoupler on the alternator pulley was bad.

I looked closely at the pulley and it looked like a regular pulley, no cover over the front and a nut was deep inside the pulley. I compared it to new decoupler pulleys available on the internet. They looked different than mine.

The numbers on my alternator body are:Toyota 27060 - 00110, 12V TN102211- 2610

A question is: did someone replace the original alternator on this car and their replacement didn't come with a decoupler pulley?

Could this alternator be the problem? One thing that might support this idea is that I measured the temperature of the alternator case after 20 minutes of running and it was 131F degrees. I don't know what the normal running temp is. Is this a high number or is this normal?

Because of the location of the power steering pump, I was unable to use the screw driver technique on it. The steering works well and it doesn't leak. Also, the A/C makes no different sounds when the clutch is in or out. The A/C works well and the water pump doesn't leak and we have no cooling problem.

Thank you for any suggestions that you may have.
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post #4 of 6 Old 02-20-2018, 04:06 AM Thread Starter
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I don't think an ADP alt came on the 2008 Matrix - I know my daughter's 07 alt doesn't have one. The alt connects to the engine block; so, it's bound to get hot, although I on't know if 131 is normal.

The bearing you haven't mentioned is the water pump bearing. Could also be the belt itself if it's hardened up or chipped or cracked. If over 100K, minus well replace it.

07 Tacoma DCLB 4X4 172K
18 Lexus RX350 10K
06 Toyota Camry I4 195K:
07 Lexus ES350 220K
07 Toyota Corolla 141K
98 Toyota Sienna 250K
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post #5 of 6 Old 02-27-2018, 03:05 PM
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Did you change the belt?

Quote:
Originally Posted by darvex View Post
I have a 2008 Matrix that was making a new sound in the serpentine belt area. I checked all of the pulleys using a screw driver, a method that I saw on You Tube that used a long screw driver with its tip placed close to the bearing and the handle was placed in the person's ear .The sounds of a particular bearing would be transmitted through the screw driver to the ear. All of the bearings sounded similar. The only unusual thing was that the tensioner was bouncing up and down by about an 1/8 of an inch.

I replaced the tensioner with a new one which had no effect on the sounds or its bouncing.

I read your post above and thought that you had solved my problem-- the decoupler on the alternator pulley was bad.

I looked closely at the pulley and it looked like a regular pulley, no cover over the front and a nut was deep inside the pulley. I compared it to new decoupler pulleys available on the internet. They looked different than mine.

The numbers on my alternator body are:Toyota 27060 - 00110, 12V TN102211- 2610

A question is: did someone replace the original alternator on this car and their replacement didn't come with a decoupler pulley?

Could this alternator be the problem? One thing that might support this idea is that I measured the temperature of the alternator case after 20 minutes of running and it was 131F degrees. I don't know what the normal running temp is. Is this a high number or is this normal?

Because of the location of the power steering pump, I was unable to use the screw driver technique on it. The steering works well and it doesn't leak. Also, the A/C makes no different sounds when the clutch is in or out. The A/C works well and the water pump doesn't leak and we have no cooling problem.

Thank you for any suggestions that you may have.
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post #6 of 6 Old 02-28-2018, 03:41 PM
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fixed

I installed a new belt less than a year ago and I inspected it the other day and it was in new condition.

I replaced the water pump because when I wiggled the pulley, it showed a lot of play that I didn't notice the last time that I tested it. After this repair, the sound went away.

Just a note: I read on a post that when replacing the serpentine belt, put the belt on the grooved pulleys first and then on the smooth ones. It also mentioned using a coat hanger to ease the mounting of the belt on the smooth pulleys.

Those 2 tips allowed me to put the belt on easily in about 10 minutes. Installation of the belt before knowing and using these tips was a terribly hard job that took me at least 2 hours--it was a killer!
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