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TB/WP - difficulty removing the lower idler arm

 
Old 06-10-2007, 11:25 PM
  #16  
mark kibort
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I dont think we even put one back on with scots rebuild. Do all 928s have the idler arm at the bottom?

MK
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Old 06-10-2007, 11:35 PM
  #17  
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Bill - you bring up a very good point. If it's not leaking - don't touch them.

My crankshaft and oil pump seals are currently leak-free. Although I have replacements on hand, I have decided to wait until the next TB/WP service to replace them, if necessary.

With proper cleaning and anti-seize on the install, at least the lower idler arm will come off without much difficulty for future service (I hope).

Thank you for your advice - I truly appreciate it!
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Old 06-11-2007, 12:19 AM
  #18  
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Originally Posted by mark kibort
I dont think we even put one back on with scots rebuild. Do all 928s have the idler arm at the bottom?

MK
In the earliest years there was just a guide plate down there with no rollers. The roller idler was first installed in MY83. The early idler has one roller and was changed to two rollers in 87. The rollers are often found frozen with no evidence of any ill effect on the belt. The rollers dampen vibrations of the belt between the oil pump and crank pulleys.

Last edited by Bill Ball; 06-11-2007 at 12:44 AM.
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Old 06-11-2007, 12:22 AM
  #19  
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Originally Posted by Adam G.
Bill - you bring up a very good point. If it's not leaking - don't touch them.

My crankshaft and oil pump seals are currently leak-free. Although I have replacements on hand, I have decided to wait until the next TB/WP service to replace them, if necessary.
That's what I did. Got the parts ready if needed. This is probably more of an issue with little used cars. Yours is borderline. You need to drive it regularly!

Last edited by Bill Ball; 06-11-2007 at 01:26 PM.
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Old 06-11-2007, 10:19 AM
  #20  
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Adam,

Glad you got it out. I didn't replace that roller or the crank gear, although I did replace all of the others. I think holding off on the crank seal is a good idea. Plenty of other variables will be replaced without messing with something that's (apparently) fine for now. Next time you do the belt you'll have the same opportunity, right?

So are you on to reassembly yet?
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Old 06-11-2007, 01:12 PM
  #21  
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Mike,

The reassembly process has been delayed slightly. The c-clips and washers that hold the lower idler arm assembly onto the pins need to be replaced. The new assembly I have didn't come with clips and washers (should have checked first) so I ordered replacements this morning.

Adam
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Old 06-11-2007, 01:43 PM
  #22  
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The rollers were on his first engine, and we put them on the last engine with the headgasket issue. however, i couldnt get it off, as those pins were a little bent and i had to use a mallet to install them, knowiing they were never coming off again! Now, when the belt was installed, those rollers (two little rollers) were not even touching the belt, AND if they ever did, well, the belt wouldnt be touching the teeth of the crank pulley! So, i didnt see a need for them, so his new engine doesnt have the rollers at the bottom.

mk

Originally Posted by Bill Ball
In the earliest years there was just a guide plate down there with no rollers. The roller idler was first installed in MY83. The early idler has one roller and was changed to two rollers in 87. The rollers are often found frozen with no evidence of any ill effect on the belt. The rollers dampen vibrations of the belt between the oil pump and crank pulleys.
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Old 06-13-2007, 08:59 AM
  #23  
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Hi All,

Last night I pulled the new lower idler arm assembly (Porsche part; not aftermarket) from the box and spun the roller bearing. It was "notchy" and did not spin smoothly like the original part that's 20 years old with 78k miles on it.

I do not think this is normal and I'm considering cleaning the old part and reinstalling that one.

Has anyone encountered a new "notchy" sealed roller bearing before?

Is it possible the grease settled in one area of the sealed roller from sitting on the shelf for some time?

Thanks,
Adam
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Old 06-13-2007, 10:12 AM
  #24  
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Bill,
You make a good point.
In my engineering career we have progressed thought various stages of the maintenance of machinery.
1. Failure, repair or by replacement
2. Planned maintenace (time based strip down based on manufacturers recommendation or by in- service experience)
3. Condition monitoring

Condition 1, not recommended with the 928
Condition 2, more damaged done during strip out, inspection and replacement. than if the unit was left untouched if operating OK.
Condition 3, if it is operating within its specification and tolerances, then leave it alone except for items that are renewed on a time basis such as the timing belt, or known problems such as the headlights "E" clip inspection on the raising mechanism and the flexplate clamp on the later auto transmission cars.
Tails 1990 928 S4 Auto
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Old 06-13-2007, 10:53 AM
  #25  
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Bill wrote
HTML Code:
In the earliest years there was just a guide plate down there 
with no rollers.
I did not bother to put my guide plate back on; after 150,000 KM it looked like new, never been touched by the TB _ I did not see the point of it.

Marton
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Old 06-13-2007, 02:40 PM
  #26  
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Originally Posted by mark kibort
Now, when the belt was installed, those rollers (two little rollers) were not even touching the belt, AND if they ever did, well, the belt wouldnt be touching the teeth of the crank pulley! So, i didnt see a need for them, so his new engine doesnt have the rollers at the bottom.

mk
They aren't supposed to touch the belt unless it is vibrating. They may not be essential, and the fact that guideplates were used successfully indicates that they probably don't absolutely need to rotate. However, I make sure they are free-moving when I do a job. If they are, I don't fuss with them other than to clean them up. When bad they can make an annoying squeak when the belt slaps them.
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Old 06-13-2007, 02:42 PM
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Originally Posted by Adam G.
Hi All,

Last night I pulled the new lower idler arm assembly (Porsche part; not aftermarket) from the box and spun the roller bearing. It was "notchy" and did not spin smoothly like the original part that's 20 years old with 78k miles on it.

I do not think this is normal and I'm considering cleaning the old part and reinstalling that one.

Has anyone encountered a new "notchy" sealed roller bearing before?

Is it possible the grease settled in one area of the sealed roller from sitting on the shelf for some time?

Thanks,
Adam
The new bearings will be stiffer but shouldn't be notchy. I would do what you did as long as the old bearings don't have a lot of play.
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Old 07-06-2010, 05:07 PM
  #28  
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Originally Posted by Adam Geist View Post
Last night I pulled the new lower idler arm assembly (Porsche part; not aftermarket) from the box and spun the roller bearing. It was "notchy" and did not spin smoothly like the original part that's 20 years old with 78k miles on it.

I do not think this is normal and I'm considering cleaning the old part and reinstalling that one.

Has anyone encountered a new "notchy" sealed roller bearing before?

Is it possible the grease settled in one area of the sealed roller from sitting on the shelf for some time?
I'm resurrecting this thread because I came across it as I was reading up on the lower idler assembly (I'm just about halfway through a TB/WP job). My '90 S4 has the two-roller version of the lower idler assembly, and my right roller on this assembly is also "notchy". It reminds me of spinning a small electric DC motor, where you can feel the permanent magnet stator / armature interaction.

FWIW, Roger (928's R Us) informed me that you can just replace the bearings (SKF 6201) instead of the whole assembly (928.105.067.01) so I just ordered two of them (among numerous other things ).

Sounds like this isn't a big deal (i.e., maybe that roller misbehaves because it's never spun or touched), but since the replacement bearings are only $6.25 from Roger, well, might as well make it right.
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Old 07-06-2010, 05:22 PM
  #29  
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Replacing the bearings is certainly MUCH more cost effective than needlessly replacing the whole part which is between $135 and $250 depending on MY. Good going to Roger for recommending this alternative.
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Old 07-06-2010, 09:33 PM
  #30  
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When I last did the TB on the 90GT and on the 88SE I also just replaced the bearings - sourced locally - about $5NZ each. All though I did question why I was doing it as it was plain from the even rust coating that the TB had never touched the rollers.
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