Notices
928 Forum
Sponsored by:
Sponsored by: 928 Specialists

Premature Timing Belt Failure - Solved

 
Old 09-01-2010, 11:52 PM
  #31  
Ethre
User
Thread Starter
 
Ethre's Avatar
 
Join Date: Aug 2010
Location: 3rd Rock From The Sun
Posts: 511
Likes: 0
Received 0 Likes on 0 Posts
Default

I'm paying a pro-wrench to replace/tension the belt. Its the side effect of having the belt slip and engine die on me driving down the road. I had to get it off the road, and was worried there could have been larger damage (interference issue, which I very thankfully found later seems to be alright on US spec 16v motors)

I don't plan on messing with the tension/changing parts unless I can verify that something needs replacing. I've got plenty of time to look over things and take it slow.
Ethre is offline  
Old 09-01-2010, 11:53 PM
  #32  
Landseer
Addict
Rennlist Member
 
Landseer's Avatar
 
Join Date: Sep 2007
Location: Frederick, Maryland
Posts: 11,326
Received 6 Likes on 4 Posts
Default

Wrong. Pro wrench must take inventory on every piece in the system. Or he's not.
Landseer is offline  
Old 09-02-2010, 12:15 AM
  #33  
Ethre
User
Thread Starter
 
Ethre's Avatar
 
Join Date: Aug 2010
Location: 3rd Rock From The Sun
Posts: 511
Likes: 0
Received 0 Likes on 0 Posts
Default

Well, I didn't mean to drag this into a discussion of mechanics. Suffice to say, I appreciate him doing exactly what I asked him to do (diagnose engine issue = turned out to be timing belt, repair = replace belt). I believe he should let me know if he notices anything, but on the other hand I didn't ask him for a detailed examination of the belt system. I think he's more worried about valve-damage (understandable, as I think he works on very few 928s). Of course I would have preferred a 928 knowledgeable mechanic, but you're right on towing adding up, and the closest I'd seen mention of was Atlanta. So, for better or worse, I took the closest Porsche mechanic with a fair reputation.

MrMerlin: I assume from the belt and oil pump gear that all the gears had been replaced with round-tooth versions? I can see the wear beginning on those teeth. Was it noticeable to hand, or just visible at that point?
Ethre is offline  
Old 09-02-2010, 12:21 AM
  #34  
Landseer
Addict
Rennlist Member
 
Landseer's Avatar
 
Join Date: Sep 2007
Location: Frederick, Maryland
Posts: 11,326
Received 6 Likes on 4 Posts
Default

Understood.

Its kind of a tough spot to be in. I get myself there all the time.

The problem is the scope of work on a 928 timing belt always includes complete review of every part, if done professionally.

This is coming from a guy who has taken the 85 car crank pulley off 4 times this year (so far) because I tried to go economy.
Landseer is offline  
Old 09-02-2010, 12:23 AM
  #35  
blown 87
Rest in Peace
Rennlist Member
 
blown 87's Avatar
 
Join Date: May 2006
Location: Bird lover in Sharpsburg
Posts: 9,903
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Ethre View Post
I'm paying a pro-wrench to replace/tension the belt. Its the side effect of having the belt slip and engine die on me driving down the road. I had to get it off the road, and was worried there could have been larger damage (interference issue, which I very thankfully found later seems to be alright on US spec 16v motors)

I don't plan on messing with the tension/changing parts unless I can verify that something needs replacing. I've got plenty of time to look over things and take it slow.
For better or worse, you need to trust the guy that is doing the work, if you feel a need to look at his work, you need to do so while he has it apart.
blown 87 is offline  
Old 09-02-2010, 12:27 AM
  #36  
blown 87
Rest in Peace
Rennlist Member
 
blown 87's Avatar
 
Join Date: May 2006
Location: Bird lover in Sharpsburg
Posts: 9,903
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Ethre View Post
I can see the wear beginning on those teeth.
Beginning?

those were wore out many, many miles ago.
blown 87 is offline  
Old 09-02-2010, 12:31 AM
  #37  
Ethre
User
Thread Starter
 
Ethre's Avatar
 
Join Date: Aug 2010
Location: 3rd Rock From The Sun
Posts: 511
Likes: 0
Received 0 Likes on 0 Posts
Default

I trust him to do the work well.
However, having not asked him to do anything beyond that, I make no assumptions about him finding anything else. I'm absolutely certain he will let me know if he sees issues, but I wouldn't expect him to go looking for additional problems beyond the tensioner/timing.
Even so, I do like to take a look at things myself. Tinker may not have been the right word.

Ouch Landseer - 4 times? I take it you are now very good at pulling it.
Ethre is offline  
Old 09-02-2010, 12:34 AM
  #38  
Landseer
Addict
Rennlist Member
 
Landseer's Avatar
 
Join Date: Sep 2007
Location: Frederick, Maryland
Posts: 11,326
Received 6 Likes on 4 Posts
Default

Yeah, unfortunately. And that's just that one.

The point is you've set-up a no-win on the car.
Can't just slap on a belt.
Gotta do it all.
Your only saving grace is its non-interference.
Landseer is offline  
Old 09-02-2010, 12:35 AM
  #39  
Ethre
User
Thread Starter
 
Ethre's Avatar
 
Join Date: Aug 2010
Location: 3rd Rock From The Sun
Posts: 511
Likes: 0
Received 0 Likes on 0 Posts
Default

I can see the curve on the left-hand side teeth, but on the middle teeth it looks as if the coating is just beginning to come off. Or is the coating really that thick (that the middle ribs could be worn to half thickness)?

But I could slap on a belt to get it out of the shop and back in my hands, correct? Kind of like a band-aid until diagnosis and cure.
Obviously it would be nice not to have to touch things after it returns from the shop, but then I run into more time and labor.
Ethre is offline  
Old 09-02-2010, 12:37 AM
  #40  
blown 87
Rest in Peace
Rennlist Member
 
blown 87's Avatar
 
Join Date: May 2006
Location: Bird lover in Sharpsburg
Posts: 9,903
Likes: 0
Received 0 Likes on 0 Posts
Default

Originally Posted by Ethre View Post
I can see the curve on the left-hand side teeth, but on the middle teeth it looks as if the coating is just beginning to come off. Or is the coating really that thick (that the middle ribs could be worn to half thickness)?
That coating is about .002 thick.

Those are about as worn as they come man.
blown 87 is offline  
Old 09-02-2010, 12:43 AM
  #41  
Landseer
Addict
Rennlist Member
 
Landseer's Avatar
 
Join Date: Sep 2007
Location: Frederick, Maryland
Posts: 11,326
Received 6 Likes on 4 Posts
Default

If the receipt doesn't show a new Porsche-supplied pump was used, I'd be changing that too, based on what has emerged about the water pump rebuild process issues. And not many mechanics even know about that. Porsche dealers don't because they use new parts. Most independents are unaware.

Not trying to bust your chops, man, but this is one job that needs the preflight check made by a pilot with a clipboard and pencil, item by item.
Landseer is offline  
Old 09-02-2010, 12:51 AM
  #42  
Ethre
User
Thread Starter
 
Ethre's Avatar
 
Join Date: Aug 2010
Location: 3rd Rock From The Sun
Posts: 511
Likes: 0
Received 0 Likes on 0 Posts
Default

Thanks Blown. Obviously my eyes need a little adjusting to dealing with these parts.

Not to worry Landseer - I've known that for a while. I realized I was jumping in the deep end when I bought it.
Ethre is offline  
Old 09-02-2010, 04:09 AM
  #43  
danglerb
Super User
 
danglerb's Avatar
 
Join Date: Oct 2006
Location: Orange, Cal
Posts: 8,550
Likes: 0
Received 1 Like on 1 Post
Default

Professional we could argue about, but NOBODY experienced with a 928 would replace a timing belt without checking the associated parts, which are the portion of the system that typically fails, not the belt itself.

Any shiny spot on the face of the gear tooth that touches the belt and the gear is worn out. There is no acceptable margin of wear for the bare aluminum, its just too soft, and the requirements too critical.
danglerb is offline  
Old 09-02-2010, 08:08 AM
  #44  
Landseer
Addict
Rennlist Member
 
Landseer's Avatar
 
Join Date: Sep 2007
Location: Frederick, Maryland
Posts: 11,326
Received 6 Likes on 4 Posts
Default

You could get it back into your own hands that way, yes. So long as the timing gears and belt profile match I think. Or pay $3/mile for towing.
Landseer is offline  
Old 09-02-2010, 08:41 AM
  #45  
WallyP

Rennlist Member
Rennlist Site Sponsor

 
Join Date: Jun 2001
Location: Acworth, GA
Posts: 6,469
Likes: 0
Received 2 Likes on 2 Posts
Default

I would not replace a working water pump on a non-interference engine.
WallyP is offline  

Thread Tools
Search this Thread
Quick Reply: Premature Timing Belt Failure - Solved


Contact Us - About Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: