The Bosch Alternator Clutch Pulley discussion

Post by **cn90** » 16 Jun 2018, 15:06

- Today, I just wonder how this system works, so did a little of experiment on my 2004 XC90 2.5T with 110K miles.

- The Bosch Alternator Clutch Pulley has been discussed in Volvo, Audi, Volvo forums for some time now.
Basically it is like a bicycle gear: allowing movement in one direction but not in the opposite direction.

- This is from my 2004 XC90 2.5T with 110K miles, but it applies to any car fit with this type of Bosch Alternator Clutch Pulley.

- EASY test: pry the cap open (long screwdriver). Think common sense: the CRANK rotates CW and with the belt layout as shown below, the ALTERNATOR PULLEY rotates CCW. Insert the T50 key as shown (belt still in place): you should be able to rotate the Alternator Pulley INNER core CCW, but not CW (think Bicycle!). If this test fails you need a new pulley (or new alternator if > 160K miles).

- Removing the alternator is no fun, I replaced the alternator in my 1998 S70 (DIY in forum) and it was NOT fun.

- Some people want to replace the Pulley in situ, so here you go, I did NOT replace the Pulley but took all the measurements for those who want to replace the Pulley in situ. All info in the photos.

- You need to buy the 33-spline tool for $7 (ebay has it).

- The GearWrench set is perfect for this in situ job.

- A little trick: hold the tool combo with your LEFT hand and insert from the middle of the engine under the turbo hose to the alternator pulley.

- Does anyone know the difference between T50 and M10 tool?

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Post by **abscate** » 16 Jun 2018, 15:28

On my 99 the Alternator pulley was left hand thread. The spline nut was really tight, too tight to release in the car, IMHO

Post by **cn90** » 16 Jun 2018, 22:18

- The Clutch Pulley has threads (very much like a Bicycle Rear Gear), which are designed that when the engine runs (CRANK runs CW), it tightens the Clutch Pulley.

- The T50 center bolt is there only to hold the Clutch Pulley in place. Actually the bicycle has no such center bolt: the foot pedal tightens the Bicycle Rear Gear as you pedal along.

- Anyway, once the T50 bolt is out, turn the Clutch Pulley opposite of the usual rotation (normal operation for the Clutch Pulley is CCW) to remove it. In other words, turn the Clutch Pulley CW to remove it.

- If you ever work on a bicycle, you will know what I referred to.

- The video below is a good one....

[youtube][/youtube]

Post by **abscate** » 17 Jun 2018, 05:16

I seem to remember me pulling on a 24 inch breaker bar and wcm standing on the alternator to counter torque my force on my 99 ( with P2 style alternator clutch)

Neither of us are twiggy.

Georgeandkira · Post by **Georgeandkira** » 17 Jun 2018, 07:47

"wcm" means what? It's not in the Urban Dictionary.

Also, it's a "Freewheel Pulley", no? I'm such a nerd.

Post by **cn90** » 17 Jun 2018, 08:23

- Now it makes even more sense to loosen the pulley while the alternator is still mounted in the car. This way you have more torque.

- With alternator in the car, undo the T50 bolt.

- Loosen the Pulley by using the 33-spline tool with the 17-mm wrench: add a second wrench using 2-wrench technique.

- Abscate, likely your pulley threads collect some salt in the winter, so it may need some PB Plaster before loosening it.
What do you think?

Post by **abscate** » 17 Jun 2018, 09:42

Georgeandkira wrote: ↑17 Jun 2018, 07:47 "wcm" means what? It's not in the Urban Dictionary.

Also, it's a "Freewheel Pulley", no? I'm such a nerd.

Abscate on the right, Wife_S70 in the middle, and wcm on the left.

Post by **cn90** » 14 Sep 2021, 06:40

Just came came across this video showing how to replace the Alternator Decoupler Pulley in situ.

Same idea as what I posted above.
- The center bolt is standard thread.
- The pulley is left-hand thread...Pulley to loosen: clockwise. Fasten: counterclockwise.

Post by **pgill** » 14 Sep 2021, 11:01

For my LR2 with the Volvo Si6 I did the following

Air impact gun CCW on the tool with the splines ran it up to 500 RPMs or so
Switched the gun to CW with it still spinning and pull the trigger and the pulley comes off

Using this technique the T50 doesn't need to be touched.

For my Audi 2.0T I removed the pulley with the Alternator still attached to the engine. This required the T50 and it was a lot more torque than I felt comfortable applying. I was surprised that I didn't break anything.

Back to Volvo

For the Si6 there are two of these clutched pulleys

The pulley for the AC, Water pump, Power Steering can be checked in under a minute.
Engine off, Move the serpentine belt at the AC compressor, it will move easily in one direction and not much in the opposite direction.

The Alternator pulley is another story for the Si6. To test it the alternator needs to come out.

Thanks

Paul

PS I changed the pulley on the Audi because the belt was moving too much but the root cause was the tensioner not the pulley (so I got to change the tensioner too)

Edit: the tool that I used for the Audi has a 17 mm hex to turn the pulley and a 12 mm Hex to hold the T50. Make sure that you are using tools that can handle 100 Ft*Lbs. Ideally the 17 mm would be turned by a quality 6 point box wrench with an extension to make it easier to turn. And the 12 mm would be held by 6 point impact socket and held or turned using a breaker bar. Note: you also need to apply pressure to the 12 mm so that the T50 stays engaged. I looked up the max torque for a T50 and one vendor had it listed at 116 ft. * Lbs. Removing the pulley almost requires three hands.

Post by **cn90** » 14 Sep 2021, 17:00

- As mentioned by @pgill above, each car is different...Audi is Hex and Volvo is Torx, but the idea is the same.
Volvo shaft is left-handed threads, while other car mfg's maybe right-handed threads...

- Depending on each car you own, just look at the belt layout and the answer is clear.

- In the Volvo P2, when the engine runs CW, the Alternator Pulley runs CCW;
because of this belt layout, the Volvo alternator shaft is left-handed, i.e., CCW to tighten and CW to loosen.

- I took some random photos from the web bc I could not find a Volvo alternator shaft that shows Torx.
So this random photo shows hex...

1. If you are skilled, you can replace the Pulley in situ.
Once the protective cap is removed, spray the inside with PB Blaster etc. and let it soak through the shaft threads for a good 30-60 min.

2. If you are lucky, then leave the serp belt on to keep friction on the pulley and turn the Volvo alternator shaft
(using Torx key) CCW to hopefully loosen the pulley. If this does not work, then use the special tool as mentioned in the first thread.
- When you turn the Volvo alternator shaft (using Torx key) CCW while the serp belt stays still,
it is the same thing as counter-hold the shaft while turning the Pulley CW.
- Just think one item (pulley) in relation to the other item (shaft) and it will become clear.
No difference than the bicycle sprocket setup...

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