Can a leaking tensioner be the sole reason for loss of timing belt tension?
01-25-2012, 04:20 PM
#32
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Although there are some excellent timing belt write ups that include the tensioner rebuild, I'm not sure any cover 82. The 82 tensioner is different than later ones. Simpler but presents some issues. First you should be sure you still have the 82 tensioner as they went NLA a long time ago and are often replaced with 83+. See the pics below. First is 82, second is 83-85. The 82 has no oil fill ports on the front. So, look for that first.
Basically, you remove all the parts as in a timing belt job. The tensioner body has 4 bolts. Take it off and take it apart by removing the end boot (part 6 below) and dropping out the internal parts carefully, observing how the conical washers (parts 9) are stacked on the rod (opposing groups of 5 washers). Clean all the parts, and for 83 and newer, replace an o-ring (second pic, part 11) on the piston and replace the end boot and its clamp. Scrape the gasket (second pic, part 2) off the 83+ tensioner and block and apply the new gasket, perhaps with some sealant to hold it in place during re-installation of the tensioner. That part can be tricky.
Most of our 928 vendors sell a kit with the parts you need. If your 82 has the original tensioner, the end boot is NLA or was last time I heard. There are ways to adapt a later boot with a "spacer" - a Dirt Devil vacuum Style 1 belt (per Dave Robert's of 928 Specialists). The 82 tensioner has no gasket and no fill ports and can be filled with oil off the car followed by the end boot. The 83+ cannot be filled until installed, sealed to the block. For 83+ you fill through the right side fill port on the front of the tensioner body until oil flows out the left. On 83-85 tensioners, you remove the plugs there completely. On 86 and newer (not shown below), these taps are exactly like brake bleeders that you loosen just a bit and leave on, attaching a hose snugly and using something like an oil can or large syringe to force the oil in until it comes out the left bleeder. 83+ tensioners have an internal Teflon coating that can get destroyed over time. You will see evidence of this coating inside somewhat shredded and rough if it is worn. In that case, the tensioner body must be replaced or the hydraulic piston will not move properly. Again, this is 83+ only.
Most of this is covered in the WSM, vol 1, section 15.
Basically, you remove all the parts as in a timing belt job. The tensioner body has 4 bolts. Take it off and take it apart by removing the end boot (part 6 below) and dropping out the internal parts carefully, observing how the conical washers (parts 9) are stacked on the rod (opposing groups of 5 washers). Clean all the parts, and for 83 and newer, replace an o-ring (second pic, part 11) on the piston and replace the end boot and its clamp. Scrape the gasket (second pic, part 2) off the 83+ tensioner and block and apply the new gasket, perhaps with some sealant to hold it in place during re-installation of the tensioner. That part can be tricky.
Most of our 928 vendors sell a kit with the parts you need. If your 82 has the original tensioner, the end boot is NLA or was last time I heard. There are ways to adapt a later boot with a "spacer" - a Dirt Devil vacuum Style 1 belt (per Dave Robert's of 928 Specialists). The 82 tensioner has no gasket and no fill ports and can be filled with oil off the car followed by the end boot. The 83+ cannot be filled until installed, sealed to the block. For 83+ you fill through the right side fill port on the front of the tensioner body until oil flows out the left. On 83-85 tensioners, you remove the plugs there completely. On 86 and newer (not shown below), these taps are exactly like brake bleeders that you loosen just a bit and leave on, attaching a hose snugly and using something like an oil can or large syringe to force the oil in until it comes out the left bleeder. 83+ tensioners have an internal Teflon coating that can get destroyed over time. You will see evidence of this coating inside somewhat shredded and rough if it is worn. In that case, the tensioner body must be replaced or the hydraulic piston will not move properly. Again, this is 83+ only.
Most of this is covered in the WSM, vol 1, section 15.
01-25-2012, 04:52 PM
#33
Drifting
Thread Starter
Bill and Merlin are correct. This mechanic is like the "doctor the doctors go to". I just spent about 30 minutes going over it in detail with Taylor. He explained everything, showing me how the bolt caused the damage. He said he would prefer to take apart the tensioner for only one reason - to make sure whoever put the wrong pump on the car without caring or knowing didn't also screw up the washers in the tensioner. He thought it was probably fine and only received a new boot and gasket. Cam gears look great.
The timing was going to change soon due to what Bill said or the belt failing the very next time I drove it. I saw the belt and the debris. Plenty of evidence on the parts it was rubbing on.
Finally, he said "The previous owner (who has a 996 and 911 that he started bringing to Taylors shop recently) takes care of his cars and always does whatever needs to be done. In this case he got bad service from a previous shop". I do know the former shop and even the technician's name -- but I'm not going there.
The pump is from a well known 928 parts vendor. The PO is suggesting trying to get the vendor to warrant the pump. Not sure how that would go.
The good news is, aside from this mishap, my mechanic thinks my car is one of the nicer ones. The PO has done everything it needed, including the timing belt and water pump. Too bad it was the wrong pump (or older version without the brace...and that pivot bolt looks inadequate to resist the torque it will experience when the roller is holding the belt tension). When I asked him what's this car worth? He said it is an $8000 car. That's substantially more than I paid for it. He said "Drive it everyday. Avoid short trips...but don't be afraid to drive it to do a day of errands and as your daily driver."
The timing was going to change soon due to what Bill said or the belt failing the very next time I drove it. I saw the belt and the debris. Plenty of evidence on the parts it was rubbing on.
Finally, he said "The previous owner (who has a 996 and 911 that he started bringing to Taylors shop recently) takes care of his cars and always does whatever needs to be done. In this case he got bad service from a previous shop". I do know the former shop and even the technician's name -- but I'm not going there.
The pump is from a well known 928 parts vendor. The PO is suggesting trying to get the vendor to warrant the pump. Not sure how that would go.
The good news is, aside from this mishap, my mechanic thinks my car is one of the nicer ones. The PO has done everything it needed, including the timing belt and water pump. Too bad it was the wrong pump (or older version without the brace...and that pivot bolt looks inadequate to resist the torque it will experience when the roller is holding the belt tension). When I asked him what's this car worth? He said it is an $8000 car. That's substantially more than I paid for it. He said "Drive it everyday. Avoid short trips...but don't be afraid to drive it to do a day of errands and as your daily driver."
01-25-2012, 05:35 PM
#34
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I like and fully agree with that. Take the long way home and enjoy the drive. Despite the hassle of modern driving with all the traffic and bad drivers, this is one of the few cars I have owned that makes driving fun again. And it might all be anecdotal, but not driving these cars often seems to do a fair amount of harm.
01-25-2012, 05:35 PM
#35
Drifting
Thread Starter
Pictures taken by Taylor during the diagnosis stage of the tear down. Notice all the black belt debris on top of the tensioner boot.
https://picasaweb.google.com/1054154...84932022787426
https://picasaweb.google.com/1054154...84935324248562
https://picasaweb.google.com/1054154...84932022787426
https://picasaweb.google.com/1054154...84935324248562
01-25-2012, 05:39 PM
#36
Drifting
Thread Starter
I don't know how to make the photos show up in the body of the post. Here's the first link again, showing the cracked cover.
https://picasaweb.google.com/1054154...84978155390690
https://picasaweb.google.com/1054154...84978155390690
01-25-2012, 05:45 PM
#37
Drifting
Thread Starter
Biil -- Taylor told me stories of several 928s and other 99X models that new owners eagerly bought because they had been in storage and "like new". He said these by far the biggest basket cases. One 99X engine needed a complete rebuild. Every seal bad. Then he told me the story of the customer with the 86 928 that he drives everyday and mostly needs only oil changes and scheduled maintenance. He is a big proponent of "They need to be driven often".
01-25-2012, 06:39 PM
#38
Biil -- Taylor told me stories of several 928s and other 99X models that new owners eagerly bought because they had been in storage and "like new". He said these by far the biggest basket cases. One 99X engine needed a complete rebuild. Every seal bad. Then he told me the story of the customer with the 86 928 that he drives everyday and mostly needs only oil changes and scheduled maintenance. He is a big proponent of "They need to be driven often".
01-25-2012, 09:07 PM
#39
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I don't know how to make the photos show up in the body of the post. Here's the first link again, showing the cracked cover.
https://picasaweb.google.com/1054154...84978155390690
https://picasaweb.google.com/1054154...84978155390690
475hp/460lb.ft
01-25-2012, 10:04 PM
#41
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01-25-2012, 10:16 PM
#42
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Unfortunate that the pics are a 'no show': there is a considerable difference between a pivot bolt and a pivot stud. the latter has M10 vs M8 base threads IIRC ..... and is counter sunk on top to take a 12mm M6 screw: this is to secure the brace that has been referred to, which was on all S4 cars, but not all '86'5's ( again, IIRC).
The OP refers to a pivot bolt .. which cannot take a brace, and is appropriate for the pump referred to ..... so it is likely the ( stronger) stud installed if the mechanic noted a missing brace
Regardless, the brace is no big deal .... cut one to shape from a piece of 1/8" stock if an OE one is unavailable, lay it on a suitable meaty area (boss) on the pump, and drill & tap a hole to tie the pump end down .... job done .... and the pump stays in service.
Quite some time ago, I did the same sort of brace mod for an earlier pivot bolt car to emulate a S4 type ( pivot bolts DO bend in service .. ergo, the 'S4 stud update), : file a flat on the pivot bolt head, drill & tap ..... and cross brace to the pump ..... again, no big deal.
The OP refers to a pivot bolt .. which cannot take a brace, and is appropriate for the pump referred to ..... so it is likely the ( stronger) stud installed if the mechanic noted a missing brace
Regardless, the brace is no big deal .... cut one to shape from a piece of 1/8" stock if an OE one is unavailable, lay it on a suitable meaty area (boss) on the pump, and drill & tap a hole to tie the pump end down .... job done .... and the pump stays in service.
Quite some time ago, I did the same sort of brace mod for an earlier pivot bolt car to emulate a S4 type ( pivot bolts DO bend in service .. ergo, the 'S4 stud update), : file a flat on the pivot bolt head, drill & tap ..... and cross brace to the pump ..... again, no big deal.
01-25-2012, 11:47 PM
#43
Drifting
Thread Starter
Garth - Sounds like a great idea, and if this were the mechanic's own car he'd probably fab a brace. I'm wondering if he (or any prudent conservative mechanic) would not suggest this to a customer because it leaves him open to liability. He's running a business and I would understand not wanting to do anything "home made" even though I bet he's already thought of it. He also puts a 12,000 mile/ 1 year warranty on all his work. He's playing it safe.
He is a very honest and great 928 mechanic. The story of how his clients talked him into going independent and giving him his own shop is great. I'm sure there are other Porsche owners on Rennlist that would echo all of my positive comments about Taylor. His place is overflowing with all models and years of Porsches whenever I visit...mostly old to new 911s, 944s, and 928s. They are lined up to pay $109 an hour. I mentioned earlier there's a 1979 928 with over 500,000 miles in the shop now. He said that engine runs strong and doesn't use oil and still has good compression.
I've seen the location for the missing brace, so this car has the S4 upgraded pump/brace design. Sorry about the pics. Maybe I need to make the album public or something. I thought the pictures would just load, not show only the URL. I'll see what I can do. The pictures are interesting.
He is a very honest and great 928 mechanic. The story of how his clients talked him into going independent and giving him his own shop is great. I'm sure there are other Porsche owners on Rennlist that would echo all of my positive comments about Taylor. His place is overflowing with all models and years of Porsches whenever I visit...mostly old to new 911s, 944s, and 928s. They are lined up to pay $109 an hour. I mentioned earlier there's a 1979 928 with over 500,000 miles in the shop now. He said that engine runs strong and doesn't use oil and still has good compression.
I've seen the location for the missing brace, so this car has the S4 upgraded pump/brace design. Sorry about the pics. Maybe I need to make the album public or something. I thought the pictures would just load, not show only the URL. I'll see what I can do. The pictures are interesting.
01-26-2012, 02:27 AM
#45
Rennlist Member
exactly! Ive never run oil in mine. i mean, i put some in, and it all leaks out. even with the brand new gasket, it came out the front boot area. so, it has some in there, but very very little.
so, the heat doesnt transfer as fast, so warm up should be a little longer before you start beating on it. the damping effects of the viscous fluid are very debatable in this application
so, the heat doesnt transfer as fast, so warm up should be a little longer before you start beating on it. the damping effects of the viscous fluid are very debatable in this application