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

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Old 02-15-2017, 07:43 AM
  #46
FredR
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Seth,

My understanding has always been that if you can feel play in the water pump shaft it is shot. The numbers you have measured also concern me. That one can measure something is inevitable but I rather suspect that on a small shaft like that the numbers you have measured seem somewhat suspect to me- hopefully our more enlightened bretheren can offer something more substantive to support you. What I can advise you is that after reading this I took a look at my spare Porsche water pump that I took from the TBF'd GTS motor some 11 years ago and the pump shaft on that is solid- no feel of any wobble whatsoever. Like you I currently have a Laso pump that I fitted two years ago and now wonder if I fitted the wrong pump! At least I have that to hand if needed.

That some oil came out of the adjuster is probably a good sign [because it is still present]. I struggle to remember the internal geometry but maybe retraction of the piston assembly causes the level to increase? As I remember the oil level should be set with the belt under correct tension but I would need to check that to be sure.

The clamp on the boot is a single use affair- that being said if push came to shove I dare say it could be pried open and then re-pinched but why bother if replacing the boot etc? As I pointed out earlier the crimp should be made at the 12 O'clock position or close to it as the area under the crimp part may not be as "well seated" as the rest of the circumference given the nature of the beast.

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Old 02-15-2017, 08:52 AM
  #47
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Originally Posted by skpyle View Post
... No idea why the bleed/fill screws were dry, and why no oil came out when I removed them.
The oil in the tensioner is not under pressure and the level should not be higher than the lower port. Thus, unless the tensioner has lost absolutely no oil - a rare occurence - removing the bleeder screws does not always result in oil dripping out. If the level of oil in the tensioner is unknown, I pump oil into it until it drips from the other bleeder. Depending upon how much goes in (and how much fresh oil you see on the ground under the tensioner) you know how empty it was.

... the tensioner roller lever bolt, it was not bent. I ...
... am not convinced that you should be convinced that your bolt is straight. Referring back to 'my' thread it took me a while to convince myself that the bolt was bent. It only takes a very small bend to throw the carrier way off at the main roller. And, the Mark I Eyeball is not very good at seeing small bends (among other things) on a typical bolt.

Thread something onto the end of the bolt (I used a die) that will act as a 'multiplier' of any wobble: something that extends 1/2" or more perpendicular to the axis of the bolt. Then, clamp the carrier in a vice and spin the pivot bolt in the carrier quickly so that any wobble is obvious.

Thought about what I am seeing: Since the bolt wasn't bent, and I found nothing else obviously wrong, could it just be that the tensioner roller lever needs to be spaced out a bit more? I don't know...
Rebuild and install your tensioner (yes the clamp is single use) and then install all the belt bits but not the center belt cover. Then, after turning the motor over a couple of times, look how everything lines up. Report back and with pictures. If there's something missing we can probably spot it. Or, at least, give you more work to do...
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Old 02-15-2017, 12:53 PM
  #48
soontobered84
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Seth,
In post #43, your pictures 3, 5, 6 ,7 and 9 would seem to indicate that those tensioner arm bushings were not changed recently. That could cause part of your issue. In addition, the play that you found on your waterpump would exacerbate under tension the belt riding towards the front.

If it was me, I would replace the water pump and those bushing and in addition, I would replace all the rollers (you don't want to have to go back in anytime soon) rebuild the tensioner, install everything to spec, say goodnight and put this thing to bed.
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Old 02-15-2017, 01:00 PM
  #49
SeanR
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Is that circlip on the large roller?
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Old 02-15-2017, 02:06 PM
  #50
skpyle
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Thanks for your replies and advice, guys!

I do want to interject with a perspective check on all this: Understand that whatever has failed, did so in 2 months and approximately 2000 miles of daily driving. I picked up the Red Witch in early May 2016, drove it every day until early July 2016. I took her off the road to do what I thought was some simple transmission and battery cable work. It spiralled badly out of control. She is still on liftbars, and has not driven since.



Kiwi'79: Not a problem, I appreciate you looking at my thread anyway. You are quite welcome! I try to document these things so that others looking can understand what I am trying to say. Also, so it can be a reference in the future when someone else gets in this predicament.



Guy: I have been reading your thread with interest. Sounds like you are having a tough time of it. Like you, I could not see any bend in the pivot bolt. Like you, I am going to replace it anyway. Probably the bushings as well.
Good Luck!



FredR: I agree, there should be NO play in a water pump shaft. This burns me because the water pump was new. My intent with the dial indicator was to try to put numbers to what I was feeling. That is my point, I was feeling definite play that I didn't think should be there. I'll be buying a new water pump and gasket.
Though, I don't necessarily think it was a failure on the part of the water pump itself. I am inclined to believe the water pump failure was caused by whatever is going wrong in the belt tensioning system.

I am definitely glad to have seen the oil start coming out of the tensioner. I will chalk that up to my own inexperience. I had assumed that the tensioner would be full of oil, and I would see oil at the ports. Worf928 has explained otherwise.
I am replacing the clamp, though the boot is still new, pliable, and undamaged. In the photos, I believe it looked grotty as a result of belt dust, and anti-seize slung off rotating components. I will clean it up. However, any sign of damage, and I order a new one.



worf928: Thank you for clarifying about the oil level in the tensioner! As I told FredR, I am chalking that up to my own inexperience with the 928. I would assume this information is in the WSM, and I missed it.

I understand what you are saying about the tensioner bolt. Last night, when I was spinning it by hand in the lever body, I thought about putting a die on the threads as a better visual indicator, as you had done in your thread. But, I didn't see any obvious movement, then got side tracked. I will do so tonight.
Regardless, I am replacing the bolt. And possibly the bushings.

Once I get the next load of parts in, I will put it all back together for a test look-see. I will reassemble the belt tensioning system and run it through several revolutions. I am assuming by hand will suffice? Or should I use the starter? I will post those results.



soontobered84: That's what confuses me. According to the invoice, the bushings were to have been replaced. Same thing with all the rollers and such. All of that was to have been new. According to the invoice, I spent a pretty penny on parts and labor for the WP change out and overhaul of the timing belt system.
As it is now, I am ordering a new water pump, new tensioner pivot bolt, and probably new bushings. I may replace the crank sprocket thrust washers just because. This hurts...




SeanR: I don't know if that circlip is there. I looked all over the lever and roller, but don't recall what I saw on the back side of the roller.
All these parts are bagged, tagged, boxed up, and in my Explorer, to go to work with me tonight. I am about to hit the bed, so I will look and get pictures tonight.


Thanks for all your help and advice!

Seth K. Pyle
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Old 02-15-2017, 02:15 PM
  #51
ROG100
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Wow! Is that the "50% off Texans discount"? My gates belt was twice that just now,
Just for the record my Gates belts are $36 8>)
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Old 02-15-2017, 02:45 PM
  #52
skpyle
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Hmmm...I wonder if I should consider a new Gates timing belt to go with everything else I am replacing.


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Old 02-15-2017, 03:19 PM
  #53
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Originally Posted by skpyle View Post
Thanks for your replies and advice, guys!

I do want to interject with a perspective check on all this: Understand that whatever has failed, did so in 2 months and approximately 2000 miles of daily driving. I picked up the Red Witch in early May 2016, drove it every day until early July 2016. I took her off the road to do what I thought was some simple transmission and battery cable work. It spiralled badly out of control. She is still on liftbars, and has not driven since.
Time to consider changing her name from the Red Witch to the Red WYAIT.
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Old 02-15-2017, 03:31 PM
  #54
soontobered84
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Originally Posted by ROG100 View Post
Just for the record my Gates belts are $36 8>)
I didn't think I was wrong about that.
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Old 02-15-2017, 04:30 PM
  #55
FredR
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Seth,

I would think it is conceivable that a problem with the tensioning system might induce a problem on the WP bearing but remember it could also be a fabrication andif so, is there a possibility of a warranty or "goodwill" claim? For sure it is a rough deal if you have to spoon out for a new pump again so soon after replacement not to mention the attendent costs for the labour.

Hopefully you can get this lot sorted and back on the road for the summer season. The joys of 928 ownership!

Rgds

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Old 02-15-2017, 05:42 PM
  #56
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did you install a new Laso Pump from Roger?
I have installed a few and noticed that the roller is moved to be more lined up ,
as if the pivot boss is machined a bit higher thus putting the roller further out from the block
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Old 02-15-2017, 07:24 PM
  #57
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Sorry Roger and John, my eyes were crossed and it was indeed $36. $83 was for the tension roller. My bad! Hoi
Originally Posted by soontobered84 View Post
I didn't think I was wrong about that.
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Old 02-15-2017, 09:39 PM
  #58
skpyle
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GT6ixer: Um...yeah. I had intended on working on my 928 to get to know her better, but this is not quite what I had in mind.
Raspberries to you, or a good 'ole Bronx Cheer.



soontobered84: That is a good thing.



FredR: That is a good point. We will find out. I will look into submitting a warranty claim on this water pump. I am back off work Friday morning. My intent is to pull the water pump Friday afternoon and go from there.
Yeah...I am pretty peeved at paying a pretty penny for all this work to be done and have it go south so quickly. But...I will keep going on and sort the details as I go.

This is in no way souring me on my 928, or 928's in general. They are a very complex, and maintenance intensive car. I am not letting a few mechanical hiccups stand in my way. Besides, I adore the Red Witch!
My intent is to have her ready for SITM 2017. So, the clock is ticking...



Mrmerlin: It is a new Laso water pump, but it was not from Roger. The WP, TB, and a bunch of other work was done to the Red Witch by a shop immediately after I bought her.

Hmmm...not sure. I am going to disassemble the roller lever and closely inspect it.



hlee96: Oops.


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Old 02-15-2017, 09:40 PM
  #59
skpyle
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OK, as SeanR requested, I have looked at the back of the roller on the tensioner arm. I do NOT see a circlip. I have removed the through bolt and nut, and found it is a shaft pressed into the arm body.

I am going to press that out and go from there.





No circlip visible on the back of the roller.





Compared to SeanR's photo, the roller shaft is pushed to the back of the bore in the arm.



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Old 02-15-2017, 09:49 PM
  #60
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Seth there is no way for the roller to turn without this snap ring .

IE if its missing then the through bolt will pull the bearing axle into the arm ,
and the edge of the roller wheel will hit the arm and grind to a halt.

That means the snap ring has to be there since it was turning with a belt on it.
BUT check it anyway, remove it to see if its is bent.

FWIW if you think a 928 is labor intensive,
try working on a 944 turbo,(951)
thats the tightest fitting machine I have ever worked on,
the 928 is like a full size Chevy pick up compared to the 951
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