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jakokombi
Samba Member
Joined: August 15, 2010
Posts: 777
Location: Milwaukee
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 Posted: Wed Sep 13, 2017 5:36 pm Post subject: 3rd broken alternator strap. |
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I replaced the alternator in my 70' (1600 sp) with a new Bosch AL82N.
Shortly after I found the hold down strap had broken. I then replaced it
with a used stock strap which also broke in short order... repeat once again.
FWIW I replaced the Bosch without pulling the engine.
Afterwards I had no rubbing of the fan and I really don't think I've been over
tightening the strap bolts or the fan belts.
In decades I've been working on my ACVWs I've never had a strap break
and now 3 in two weeks time??
Thoughts?
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51121
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Wed Sep 13, 2017 5:52 pm Post subject: Re: 3rd broken alternator strap. |
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Where are you getting these straps from?, new?, or good used German?
Sounds to me like you need another fan that maybe isn't so horribly out of balance.
Describe your method for belt adjustment as well please.
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jakokombi
Samba Member
Joined: August 15, 2010
Posts: 777
Location: Milwaukee
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| Posted: Wed Sep 13, 2017 6:17 pm Post subject: Re: 3rd broken alternator strap. |
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Used German straps.
I usually tightened the pulley nut snug, then let the pulley turn as I
tightened more so that the belt can ride higher in the groove,
then hold it down for final tourque. Shims placed so that I can get maybe
a half inch of belt deflection.
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Manfred58sc
Samba Member
Joined: October 05, 2009
Posts: 3382
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| Posted: Wed Sep 13, 2017 7:32 pm Post subject: Re: 3rd broken alternator strap. |
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Bent shaft, I've had it happen in the past. It is not noticeable at low speed , but it will repeatedly snap the strap.
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scrivyscriv
Samba Electrician
Joined: October 04, 2011
Posts: 2922
Location: Memphis
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| Posted: Wed Sep 13, 2017 9:55 pm Post subject: Re: 3rd broken alternator strap. |
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| Manfred58sc wrote: |
| Bent shaft, I've had it happen in the past. It is not noticeable at low speed , but it will repeatedly snap the strap. |
If it is a bent alternator shaft, you will be able to find it with a dial indicator (remove the pulley and fan, check with the indicator tip directly on the shaft:
Link
For the strap, I use what I think is a much better solution, commonly used in aviation for other stuff.. a stainless band clamp.
https://www.thesamba.com/vw/classifieds/detail.php?id=1379800
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airschooled
Air-Schooled
Joined: April 04, 2012
Posts: 12721
Location: on a bike ride somewhere
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| Posted: Thu Sep 14, 2017 1:02 am Post subject: Re: 3rd broken alternator strap. |
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EMPI makes those, and I find the quality to be excellent. At first I had questions about the stainless' ability to deal with vibration without work hardening, but 60k miles has proven mine to be effective. You WILL ned a 10mm deep socket to fully tighten the strap, unlike the stock strap which can be done with a regular 13mm socket and box wrench.
Robbie
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Manfred58sc
Samba Member
Joined: October 05, 2009
Posts: 3382
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| Posted: Thu Sep 14, 2017 6:31 am Post subject: Re: 3rd broken alternator strap. |
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Nice video posting! I like the Chinese gauge measuring the failure of a Chinese alternator. You can see the wobble when the rotation occurs. Mine was more subtle, hard to see except at high rpm.
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jakokombi
Samba Member
Joined: August 15, 2010
Posts: 777
Location: Milwaukee
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| Posted: Fri Sep 15, 2017 6:29 am Post subject: Re: 3rd broken alternator strap. |
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Ok, I discovered that the culprit was a bad pulley that I didn't notice in my haste to get back on the road.
It was an original cast pulley that had been worn on it's inner bore causing some eccentricity.
The alt shaft run out was good and I've got a good pulley on there.
Just gotta find another strap and new belt.
Thanks guys!
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appetite
Samba Member
Joined: September 28, 2004
Posts: 127
Location: New Jersey
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| Posted: Sun Sep 17, 2017 1:33 pm Post subject: Re: 3rd broken alternator strap. |
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jakokombi,
Not to highjack your thread, but I'm curious about your alternator swap. You mentioned that you did it without removing the engine. Besides removing the nut behind the fan shroud, which I understand is a huge PIA, did you encounter any other difficulties?
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51121
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sun Sep 17, 2017 2:30 pm Post subject: Re: 3rd broken alternator strap. |
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| appetite wrote: |
jakokombi,
Not to highjack your thread, but I'm curious about your alternator swap. You mentioned that you did it without removing the engine. Besides removing the nut behind the fan shroud, which I understand is a huge PIA, did you encounter any other difficulties? |
Sometimes the nut puts up a fight, but most of the time a strap wrench or oil filter wrench on the pulley will break it loose. Aside from removing the carb the only other occasional issue is getting at the lower plate fasteners between the manifold and shroud, if they are slot screws and not hex head they are tedious to remove. Getting all the shims/washers aligned and the nut back on requires eyes on the ends of your fingers but if you do a few dry runs out of the bus you can get a feel for it first.
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jakokombi
Samba Member
Joined: August 15, 2010
Posts: 777
Location: Milwaukee
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| Posted: Sun Sep 17, 2017 2:52 pm Post subject: Re: 3rd broken alternator strap. |
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| appetite wrote: |
jakokombi,
Not to highjack your thread, but I'm curious about your alternator swap. You mentioned that you did it without removing the engine. Besides removing the nut behind the fan shroud, which I understand is a huge PIA, did you encounter any other difficulties? |
Yes it is a pain. More importantly, it is a hack way to do it.
If you look at our Great Green Book (Bently manual) it says that there is a precise measurement for fan clearance in the housing which would be difficult if not impossible to achieve with engine in.
As far as other problems, access to the fan plate housing scews can be difficult (I use cap head screws on my tin). If that fan nut hasn't been off in 40 plus years it will not come easily.
Truly it is easier to pull the engine on an early bay and do this job correctly. The only reason I did it this way was that I knew that if I dropped the motor, then I would feel the need to address a bunch of other things that would run me out of time and make me miss the eclipse trip, things like new clutch? very minor exhaust leak and whatever else I would pick at while I was there. Also I knew it would come easy because I had put it in recently.
I had a large bruise on my inner forearm from the fan shroud for several days afterwards.
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busdaddy
Samba Member
Joined: February 12, 2004
Posts: 51121
Location: Surrey B.C. Canada, but thinking of Ukraine
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| Posted: Sun Sep 17, 2017 3:23 pm Post subject: Re: 3rd broken alternator strap. |
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| jakokombi wrote: |
| ......If you look at our Great Green Book (Bently manual) it says that there is a precise measurement for fan clearance in the housing which would be difficult if not impossible to achieve with engine in.... |
Well to split hairs the measurement is between the generator plate (disc) and the front of the fan, and regardless of where the engine is sitting that has to be done by assembling the fan to the alternator while it's out of the shroud. The difference when doing it while the engine is installed is you have to remove the fan again and put it into the shroud first, just make sure you keep the shim stack intact and the clearance will be the same after it's back together. There's nothing "hack" about it if you take your time and measure first.
As for the bruised forearm?, yeah, that's part of cheating the flat rate time on a job, if your arms can't take it drop the engine.
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Please don't PM technical questions, ask your problem in public so everyone can play along. If you think it's too stupid post it here
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Manfred58sc
Samba Member
Joined: October 05, 2009
Posts: 3382
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| Posted: Sun Sep 17, 2017 4:19 pm Post subject: Re: 3rd broken alternator strap. |
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Cut a nice access hole in the luggage area (just the size of a late T-4 powered access hatch), remove the shroud and alternator as one unit, service as necessary and re-install. In this day of horrid Chinese parts this is not a hack but a necessary upgrade . Pulling the engine every time an alternator fails is insane (they only last 10K miles if your lucky) , and doing it in place is really hard .
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Tcash
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Posts: 12844
Location: San Jose, California, USA
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| Posted: Sun Sep 17, 2017 5:44 pm Post subject: Re: 3rd broken alternator strap. |
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appetite
Samba Member
Joined: September 28, 2004
Posts: 127
Location: New Jersey
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| Posted: Mon Sep 18, 2017 3:30 pm Post subject: Re: 3rd broken alternator strap. |
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Thanks all. I'll bite the bullet and pull the engine.
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airschooled
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Joined: April 04, 2012
Posts: 12721
Location: on a bike ride somewhere
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| Posted: Tue Sep 19, 2017 10:38 pm Post subject: Re: 3rd broken alternator strap. |
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| appetite wrote: |
| Thanks all. I'll bite the bullet and pull the engine. |
Wooooaaaahhhhh. Tell us about your engine first. If you don't have a thermostat, you'll be able to do it much easier. If you don't have a doghouse shroud/oil cooler, you'll be able to do it in even less time.
With the right 36mm socket wrench, and a good diagram of how it goes back together, the job can be done with less physical effort and more physical dexterity in about the same time, or less.
Robbie
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