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Help me understand what I am seeing with my timing belt...

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Old 02-10-2017, 03:33 PM   #16
FredR
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Seth,

Seems you have eliminated belt tension as an issue here.

At least you have plenty to work with regarding the belt tracking. I see nothing obvious on the cam sprockets to warrant intervention. The gasket at the back of the tensioner looks new but the boot on the tensioner looks a bit grotty. I also understand it is recommended for the crimp to be pinched at the 12 O'clock position if my memory serves me correctly.

Hopefully you will get to the bottom of any issues quickly.

Rgds

Fred
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Old 02-10-2017, 05:43 PM   #17
Mrmerlin
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FWIW that is how the tension should look at the top of the window.
roll the engine over again to TDC and check it,
it might move some
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Old 02-10-2017, 06:18 PM   #18
soontobered84
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Seth,
I'm glad you found your wire.

That timing belt part number is probably correct, but I don't think Conti makes OEM. I believe Porsche OEM is Gates. IIRC Roger sells Gates for something less than $40, but I could be wrong about that. Apparently someone paid double retail for that Conti belt. I had a Conti belt on my 89 and had numerous problems with false timing belt warnings from what I perceived as stretching (At least that's what I attribute it to, since there is currently no way to measure the tension while the engine is running) I changed to a Gates belt and had no further issues with false timing belt warnings. Note: others have used Conti belts and had no issues. I just got to be one of the lucky ones, I guess.
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Old 02-10-2017, 06:28 PM   #19
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Quote:
Originally Posted by soontobered84 View Post
Seth,
I'm glad you found your wire.

That timing belt part number is probably correct, but I don't think Conti makes OEM. I believe Porsche OEM is Gates. IIRC Roger sells Gates for something less than $40, but I could be wrong about that. Apparently someone paid double retail for that Conti belt. I had a Conti belt on my 89 and had numerous problems with false timing belt warnings from what I perceived as stretching (At least that's what I attribute it to, since there is currently no way to measure the tension while the engine is running) I changed to a Gates belt and had no further issues with false timing belt warnings. Note: others have used Conti belts and had no issues. I just got to be one of the lucky ones, I guess.
Wow! Is that the "50% off Texans discount"? My gates belt was twice that just now,
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Old 02-10-2017, 06:37 PM   #20
Crumpler
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Nice thread Seth, keep up the good work.

Hey, in terms of the wear on your cam gears, I thought they looked good to go for longer, especially if the belt is tracking well when you are done. Just my two cents. Same for the oil pump gear.
Unless, the project is still under budget
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Old 02-10-2017, 09:54 PM   #21
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Quote:
Originally Posted by skpyle View Post
I will remove the bolt and inspect it. According to the invoice, the bolt was replaced. What causes this bolt to get bent?
On the S4 tensioners, the pivot bolt does not need to be removed to withdraw the tension roller carrier. So, it's really hard to do anything 'weird' with the pivot.

However, on the pre-S4 tensioners, depending upon how/when you install the carrier and bolt, it's very easy to accidentally bend the bolt.

If you search back about two years, you will find a thread started by yours truly wherein I'm asking the collective for help on how I could have bent two pivot bolts during install...

... turns out, that when you turn-in the pivot bolt, the outer edge of the main roller can bind on part of the water pump casting (IIRC, but, my discovery and conclusion is in that thread) if the carrier is rotated too far counter-clockwise.

This last bit is really easy to do, because you're working 'around' the belt and the tensioner plunger that has to seat in the tensioner boot, so it's natural to rotate the carrier to allow the plunger to clear the bore in the boot as you turn-in the pivot bolt / carrier assembly. Then as you turn in the pivot bolt the last two or three turns you're using the bolt as a lever to try to bend the carrier. Of course, the bolt is going to bend, not the carrier. If you have changed the plastic bushings in the carrier, the force needed to turn the bolt in the bushings is great enough that you can't 'feel' that you're bending the bolt.

Of course, none of that is an excuse for leaving the tensioner dry.

Last, but not least, it might not be that the pivot bolt was bent on install.

A dry tensioner will 'cause' the belt to become way-over-tight under certain conditions. Since the pre-S4 setup has no cross-brace on the pivot bolt, I could - will - opine that the pivot bolt will bend before a Gates belt will stretch enough to 'loosen.' (But, I can't be certain without doing experiments that no one really wants to do.)
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Old 02-11-2017, 04:26 AM   #22
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FredR: Thanks. I freely admit I screwed up the initial belt tension reading.
I understand what you are saying about leaving the cam sprockets be. Thanks for the advice.
The boot on the tensioner is supposed to be new. I am going to remove all the tensioning components for cleaning and inspection. When I fit the new clamp, I will put the crimp at 12 o'clock.
Thanks!



Mrmerlin: Stan, I appreciate the clarification. I have never used the Kempf tool before, and have not fully researched what is considered 'good'. I had thought in the middle was the target. I will roll the crank several more times, checking the tension every two rotations. I will report what I find.
Also, I have ordered some Hondabond 4 for the new tensioner mounting gasket.



soontobered4: Thanks! Yep, I had found the wire and didn't even know what I was looking at.
As for the belt, hmmm... I am hoping to be able to continue to use this one, as I would think it has stretched and taken a set. However, if need be, I will order a new Gates belt.



hlee96: Nice. I hope to not have to find out what a new Gates belt costs, but we shall see.



crumpler: Thanks for the perspective on the sprockets. I am going to leave them alone. Under budget? Lordy Jesus, I am already running around $1500 OVER budget...
Also, thanks for the encouragement, I do appreciate it.



worf928: That is some good, solid information, Thanks! I am going to pay close attention to the pieces as I disassemble everything. I will report my findings on here. I will definitely heed your warning during reassembly.
As for the tensioner, I am concerned about what I will find inside...
Thanks! I will hunt for your thread.


Thanks guys!

Seth K. Pyle
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Old 02-11-2017, 04:47 AM   #23
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AHA!!! worf928, I found your thread and read all of it. Very enlightening...

https://rennlist.com/forums/928-foru...l#post13950999


I went back and looked at my photos. My timing belt is also running off the tension roller. Go to the 10th photo in my first post. It looks just like worf928's did in the 3rd photo in his first post in his thread.

This gives me something to be on the look out for. I will definitely pay close attention to each and every piece of the tensioning system as I disassemble it.

Thanks!

Seth K. Pyle
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Old 02-11-2017, 06:57 AM   #24
FredR
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Seth,

The Kempf tool is designed to be set in the middle of the window. However, many have noted that when compared to the expensive factory tool the Kempf equivalent position is at the top end of the window range. That being said, when Jay developed his tool he found it had better repeatability than the factory tool so which does one believe? The safer bet is to go with the factory tool calibration however accurate that may be.

Personally I rely on the Kempf tool at mid range. Have never had an alarm or any signs of distress. With belts in general I have a tendency to tighten them as slack as I think I can get away with- occasionally I get it wrong.

Rgds

Fred
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Old 02-11-2017, 11:25 PM   #25
Mrmerlin
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set the belt to to the top of the window,
when the new belt stretches then the pointer will come back towards the center,
at some point you will have the warning going off, so an increase in tension will be required.

NOTE with the Kempf tool the 32 V engines should have the pointer to the top of the window,
and the 16V engines at the low end of the window
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Old 02-12-2017, 02:31 AM   #26
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Quote:
Originally Posted by Mrmerlin View Post
set the belt to to the top of the window,
when the new belt stretches then the pointer will come back towards the center,
at some point you will have the warning going off, so an increase in tension will be required.

NOTE with the Kempf tool the 32 V engines should have the pointer to the top of the window,
and the 16V engines at the low end of the window
I've never used the Kempf tool (or even had one in my hands), but it was my understanding that it was a copy of the early factory tool, for the 2 valve engines.

If that is the case, it would seem that the range in the adjustment window was for the early engines. (4.5+/-.1.)

Seems like 5.0+/-.1, for the later belts, would be have to be much higher on the Kempf Tool scale?

But does anyone have a direct comparison of the Kempf tool to the 9201 tool on both early and late belts and care to share this information?

Please realize that I've just been reading a strange rationalization (on another thread), that 4.5 is exactly the same as 5.0, when using an Audi hydraulic tensioner.....and that left me more than a little bit confused....but I'm guessing (hoping) 4.5 is different than 5.0 when using a Kempf tool?

The reason I'm asking is that I've got a client (actually two) in Virginia who is about due for a belt adjustment on a new engine I built for him/them and I'd like to tell him that he can use the simpler Kempf tool, if possible.

Thanks, all!
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Old 02-12-2017, 07:45 AM   #27
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Quote:
Originally Posted by GregBBRD View Post
Seems like 5.0+/-.1, for the later belts, would be have to be much higher on the Kempf Tool scale?
It is. The later belts are 5.0 - 5.3 on the 9201.

Quote:
But does anyone have a direct comparison of the Kempf tool to the 9201 tool on both early and late belts and care to share this information?
5.0 to 5.3 corresponds to the last 20% of the 'window' and 4.5 is center of the window...

... on my Kempf tool which I've calibrated with my 9201.

I've measured two other Kempf tools and there was - IIRC - a 10% variance between the three.

On a good condition Kempf tool, that is uncalibrared against a 9201, I would set the belt at 90% which should be in the 5.0 to 5.3 range. (For a 32v engine.)
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Old 02-12-2017, 08:41 AM   #28
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Sweet! That is good to know.


Seth K. Pyle
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Old 02-12-2017, 09:25 AM   #29
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Of course the only way to verify any of this is to have a 9201 tool to calibrate your Kempf tool to start with,
and a belt to test it on,
I have 3 Kempf tools and I have adjusted and calibrated via the 9201 on a HTD belt.

it also has to be realized the Kempf tool is not as accurate as the 9201 tool,
but for belt tension its good enough and is repeatable.

if your tool is calibrated then setting the tension as I suggested will put the belt tension in a safe place for continued operation ,and without setting off the belt warning if so equipped
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Old 02-12-2017, 10:04 AM   #30
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As I remember the instructions for the Kempf tool, there was no distinction between the 16V and 32V models. I have seen an original 16V factory tool and indeed they are very similar in looks and function the same way but whether they are identical [copyright?] I know not. I assumed it was appropriate for my S4 motor but did not ask a specific question in that regard.

I ordered the tool a few years ago given I planned to my own spanner work and when the tool arrived I immediately used it to check the tension on my [well used] 32V belt- the reading was bang in the middle of the window so left well alone given I had no apparent issues other than some sprocket coating degradation.

A year or so later I did my first timing belt/WP job and set it at the top end of the scale expecting it would slacken off a bit and checked tension after about 1000 miles. The reading was mid scale by then so once more left well alone.

Regarding calibration I have no idea how you chaps with the 9201 tool calibrate it but hopefully you have something to calibrate it against [or do you send it off to a lab somewhere to check it every so often?] as such is usually the order of the day when it comes to critical instrumentation.

I remember an interesting comment in the Kemp instructions that to help ensure the calibration is maintained one should put a spot of penetrating oil on the pivot for consistency of reading. For sure my Kempf tool is carefully packed away after each use to keep dust etc out and not chucked in a box with other spanners and other assorted horse manure for company!

Dave's comment shows he saw a value spread of 10% over 3 such gauges in whatever condition they might have been - it might be interesting to know how consistent the readings would be if the 9201 reads a given belt 3 times in succession. One expects them to be pretty much the same but...?

I will be checking belt tension in a few days time so it will be interesting to see if the Gates belt has maintained tension since last year or whether it has slackened off at all. The other variable I have wondered about is ambient temperature. Daytime temps currently hover around 24C at this time of year. I have often wondered if the temps dropped to say zero C whether I would see a measureable drop in static tension. One assumes that Porsche expect the temperature in a workshop to be something reasonable say around 20C. Thus why I check my belt tension at this time of year and not when it is 44C ambient!

Rgds

Fred
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