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Timing and Balance Shaft Belts

 
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wawaloon  
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PostPosted: Wed Sep 04, 2002 5:41 am    Post subject: Reply with quote

Hello Everyone, I just completed my first Timing belt change on my new (to me) 87 924S and I performed the operation in meticulous fashion, taking great pains to learn the in's and out's of the job and all seems to have turned out well except for a distinct belt whine that I now have. As advised by elsewhere on this site, I set the tension on the new timing belt to 4.0 and the new Auxiliary shaft belt to 3.0 but still there is a whine. I’m not sure which belt is causing the whine yet but I will do so through the process of elimination. Is it normal to have some whine on these cars as the belts break in or should they be silent through the 2000 miles before the re-tensioning? Thanks in advance for any advise. Good Day! M. R. Ganshirt.
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Paul  
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PostPosted: Wed Sep 04, 2002 12:01 pm    Post subject: Reply with quote

Its usually the idler pulley for the balance shaft belt, back it away from the belt and see it the noise goes away.

Anyone know why Porsche didn't put teeth on this pulley? It has never made sense to me why this pulley has a flat surface for the teeth of the belt to grind against.
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wawaloon  
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PostPosted: Wed Sep 04, 2002 8:15 pm    Post subject: Reply with quote

Hey, thanks Paul, the Idler Pully makes perfect sense now that you mention it. I will give that a try today. Thanks again. M. R. Ganshirt.
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Paul  
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PostPosted: Sat Sep 07, 2002 1:02 pm    Post subject: Reply with quote

This guy really has the idler pulley backed off!

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wawaloon  
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PostPosted: Sat Sep 07, 2002 9:20 pm    Post subject: Reply with quote

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wawaloon  
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PostPosted: Sat Sep 07, 2002 9:31 pm    Post subject: Reply with quote

Yes indeed, that pully is backed way off. This idler is mostly to pick up "slap", is it not? The beast could run fine indefinitely without it, no?
I must say, with all of the nasty stories that I have read about replacing and maintaining these belts and the potential consequences involved I have been pretty paranoid about getting the detailss spot on but really I found the work to be straight forward.
Using my $500 tensioning tool I did discover that the factory tensioner was a bit on the weak side so I'm glad I bought the gadget.
It looks like I will be pulling the whole set-up apart again in the coming months because some of my seals are a bit leaky and I might as well replace the waterpump while I'm at it.
Now, if I can line up a couple of owners these cars, so I can do their belts as well, I just might make my money back on the tensioner.
Does anyone know what a Porsche dealer charges for this work?

Thanks, Michael.
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Paul  
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PostPosted: Sat Sep 07, 2002 10:26 pm    Post subject: Reply with quote

I'm sure someone will have a better answer, but I've heard its about $400 if just the belts are replaced, $700 for belts, balance shaft seals, and idler pulleys. More if the water pump is replaced.

Remember if you do this for someone and it fails, you will be expected to fix the bent valves for free. Always include the 2000 mile adjustment in the original bill so the customer has no reason not to return on time.


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wawaloon  
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PostPosted: Sat Sep 07, 2002 11:48 pm    Post subject: Reply with quote

True enough, there is a fair amount of risk involved in performing this on other people's cars. I wouldn't dare tackle such jobs without being comfortable on my own 924S first.

I should have a good amount of hands-on experience with my own by this time next year and absolutely, the 2000 mile re-tensioning requirement is an essential and mandatory element of the job.

Really, the tool pays for itself in the first belt replacement and especially with the 2000 mile retensioning.

People who own these cars and who don't wrench them themselves must either pay through the nose for these jobs or ignore the factory recommendations and run the risks.

These belt issues seem to be the Achilles heal of these cars- otherwise they seem very robust and reliable. Do these belts really fail as often as I get the feeling they do?

Thanks, Michael
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wawaloon  
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PostPosted: Sun Sep 08, 2002 1:23 am    Post subject: Reply with quote

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wawaloon  
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PostPosted: Sun Sep 08, 2002 1:35 am    Post subject: Reply with quote

OK, now this is getting interesting, the belt whine I have on my 924S persists despite my efforts to remedy it.

I backed off the balance shaft belt idler pulley in effort to get rid of the whine noise from the belts and the sound remained. So this morning I lessened the tension on the balance shaft belt itself to see if this would remove the whine but it did not.


Yikes!

What remains, as a cause of the whine is the timing belt. This I tensioned to 4.0 per recommendations. I rechecked it repeated times this morning and it is indeed at 4.0.

I would like to trust the tension that I have set but I can't bring myself to believe that the whine I am hearing, however slight, is normal.

Does anyone have any further advice or experience that they can share?

Thanks in advance, Michael G.
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gohim  
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PostPosted: Sun Sep 08, 2002 8:10 pm    Post subject: Reply with quote

The "whine" is normal after a camshaft and balance shaft belt replacement.

If the front oil seals are leaking, you should not have reassembled the front of the engine without replacing them. Motor oil causes the belts to weaken and breakdown sooner than they would have. There is no way to clean oil contaminated belts. You need to go back in asap and replace all of the parts that should have been replaced.

Recommended belt replacement maintenance schedule is replacement every three years, or 30K miles, whichever comes first. First Critical belt retension is at 2K miles, then belts are to be inspected and retensioned every 10K miles till replacement.

Replacement of the front oil seals, rollers, pulleys, and water pump is recommended at every belt change, because the failure of any of these components would cause belt failure, and the replacement of any of these parts would require the removal of the belts which is the bulk of the labor charge that you would pay anyway.
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wawaloon  
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PostPosted: Sun Sep 08, 2002 9:53 pm    Post subject: Reply with quote

Thanks Very Much For The Reply, How long does this "whine" last, generally?

I agree that I really should have replaced all the relevant oil seals and the waterpump during this maintenance but I hadn't anticipated the oil problem (based on the prior owner's [now bad]info regarding the car's condition).

Knowing that these problems exist I will simply perform the entire job over again in a month's time-I need the car back together and drivable . Belts are relatively cheap anyway and the second time around the job will be an infinitely faster affair. Good practice in any case.

While on the subject, does anyone have any experience with these waterpumps? Are the factory replacements worth the extra cash or will an aftermarket or rebuild piece do the trick just as well for cheaper?

Thanks All, Michael.
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Michael Kouridakis  
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PostPosted: Mon Sep 09, 2002 10:58 am    Post subject: Reply with quote

Hey guys,
About how long did it take you to do the belts? I have to do mine soon and I'm trying to figure out how much time to set aside. I have an '88 951 so I don't need the expensive tensioning tool, right? I'll replace the seals and water pump tool. I'm driving it out to the Indy F1 in a couple of weeks and I don't want to take any chances.
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wawaloon  
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PostPosted: Mon Sep 09, 2002 11:23 am    Post subject: Reply with quote

I would be a poor guage for the job because I REALLY took my time and fiddled around with the mechanicals quite a bit, to learn as much as possible about it. At least four to five hours might be a reasonable estimate.
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Paul  
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PostPosted: Mon Sep 09, 2002 12:25 pm    Post subject: Reply with quote

Mike,

You should use the tensioner tool for both belts. You will also need a tool to hold the balance shaft pulleys while you back off their bolts so that you can replace their seals. Be careful, I believe one of the seals is smaller than the other. When replacing the water pump, you will need a heavy duty snap ring tool to remove the thermostat.

Its also a good time to replace all the radiator hoses, especially the one that attaches to the water pump. Same for the power steering and A/C belts.

If you've never done this, plan for a whole day.

Remember if you mess this up, you will destroy at least your valves.

Make sure you have access to the factory manual for the procedures and torque values.

Good luck!
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