fraggle

If I have timing belt failure of some kind with the porkentioner, I'll rebuild me motor and reinstall it on the new one.

Switch it and forget it for a few dozen thousand miles!

Captain_Slow

All,
Thanks for excellent replies. Fascinating how the tensioner works. In depth and easy to understand. The tension light came on for just a few seconds before I shut off the engine. Then I restarted it (I know) and let it run for 20 minutes. No light. Turned it off again and then started it again and ran it until it was fully warmed up. Still no warning light. But, a peak through the vent holes on top of the belt/cam gear covers revealed the belt was riding flush with the front of the gears. Something's up.

I called the previous owner and asked if it was a new or rebuilt pump. His immediate response was "It's a new Lasso pump with metal impeller".

It does have a Continental belt. He has been retensioned once before at about 1500 miles when the tension warning light came on.

Could improper tension on other belts contribute to this?

fraggle

If I had a tension light come on I wouldn't be satsified until I pulled all the covers off for a thorough inspection.

Good luck!

Captain_Slow

Where I live now I can't pull covers, change oil, rotate tires... Condo association cracking down - police have been called a few times (not on me). Impulse buy...lesson learned. Taking it to the shop. Will drive it until I feel I've got value out of the repair or stop caring. Will probably keep if "always for sale" for a fixed price until I just want it gone. Meanwhile, I'll enjoy it and use it. Cars aren't hobbies if I have to pay someone to work on them, so no more until I have a garage again.

Bill Ball

I don't think the belt should ever get so loose that the light comes on, even before the 1500 mile adjustment. If the belt was tensioned properly on installation and everything else is in good condition, it should never get that loose. If you find it loose this time, well after the 1500 mile check at which it was re-tensioned, then I would be very concerned. The belt riding forward is sometimes due to worn plastic bushings on tensioner arm pivot. This allows the arm to tilt and could reduce tension as well. There should be no play in the pivot. Possibly the bushings were not replaced as they should be almost without exception with each belt. This can't be checked without removing the side and center covers. I had one similar experience with a Conti belt - light came on briefly, I checked tension, which was OK, then a month later the light came on and stayed on. It was loose and I changed it. I found nothing else wrong, but it is true my tensioner was not holding oil at that time. Still, I've had several other belts with a mostly dry tensioner and did not encounter looseness.

jeff spahn

time to move

Bill Ball

Hah, hah. I agree.

rgs944

Yea, but I bet he meets more hot chicks than we do. Everything is a tradeoff, is'nt it? . lol

WallyP

Start a new thread asking for help in your area, and see if another 928 owner in the area has shop availability and willingness to help...

Captain_Slow

What a coincidence....two hot chicks walking their dogs came over just as it's being pulled up on the flat bed to go to the shop...."Oh...what a tragedy...I love the older ones, especially 928s. It's beautiful. They look so much better than the new ones". Funny how Porsche being towed gets more attention than a healthy one Even while driving ahead of the tow truck, leading the way to the shop, I saw lots of people checking out the 928 riding high. One driver somehow sensed that I was the owner leading the truck and pulled up along side and gave me a nod and then settled back to check out the car again. That was kind of odd.

I appreciate the encouragement to find a place and some local helpers to work on it. I know I can fix it myself, but this feels like it could end up not getting done for a long while. Insurance covered the tow to the shop today. Spent the afternoon going over it with mechanics. Quickly confirmed the tensioner is leaking. They agree the first thing to check is the tensioner arm bushings, as the way they tend to fail causes the arm to twist and push the belt toward the front of the cam gears.

We got to talking about how the business started only 6 months ago but has so many clients (based on the number and variety of Porsches at the shop). A group of clients approached Taylor and asked him to ditch the well-known shop he worked for and go independent (all but a few clients followed). One of the customer/investors who put in most of the capital has an 86 928 as daily driver and a GTS. There were three 928s in the shop today, including a 1979 with over 500,000 miles. He's worked on 928s for more than 20 years, during which he's only had to rebuild ONE engine. When I asked "how long will a well cared for 928 engine last?" He said "I don't know...probably forever."

I'll hear from them next week about what they find, suggestions, and costs.

Thanks for the responses and explanations of how the tensioner works, fails, and other possible causes of the loss of tension. Unfortunately, I don't have time to work on this until August, and no idea where I'd do it. Letting it sit that long without being able to start it is not an option.

Jon

Captain_Slow

Some here may find it interesting to read what the mechanic found. If someone will tell me how to post the pictures in the body of a post I'll post them. Turns out the tensioner is not leaking, but the there were other issues. Here's the mechanic's report: (note the water pump is new Laso, but wrong one)

Jon,
Yes you will need the center timing belt cover(928 105 144 04, somewhere close to
that # as they change/update periodically).
I recommend a lottery ticket as the belt was very close to failure.
The pivot bolt was working its way loose and had actually cracked the
belt cover. There is belt debris on the tensioner boot.I am going to
fill the tensioner reservoir to see if its leaking or just empty. The
crank seal is leaking along with the front of the oil pan( may be able
to tighten bolts). The water pump is an older style, and should have
been updated to the style with the support bracket. You will see in
the pictures there is no support bracket. I am sending pictures via
iphone in the next few minutes.
I am working on an estimate. Did you say you had a water pump? Is it
in the car?.You are of course welcome to come by and inspect.
Thank you,
Taylor

Jon,
Yes the pan gasket is new and one of those 'leak proof' ones.The
front crank seal seams to be the culprit on the oil leak. The
tensioner is holding oil and the gasket looks OK. the boot is holding
pressure. The pump is not damaged or leaking so I dont think there is
any problem with the block. I will see if I can get an update kit for
this pump . But for some reason I dont think it is available anymore
and the only way to put this back together properly is with the pump
that uses the support bracket. Hence the reason they did away with
this bolt style.
I will get some $#s to you as soon as I can.
Yes it is the same cover that you need that cracked. The other covers
are fine . So just the center cover is needed. The crack is from the
bolt trying to come out that holds the tensioner roller for the cam
belt.I figured that would be a great picture to have the 928 people
would love that one.
Thanks,
Taylor

Jon,
Tensioner arm bushings were very stiff on the bolt. Arm and all is
good. I need to look into whats available for update/ replace. As far
as running, the cam timing was still correct, but wasn't going to be
for much longer. Andrew said you called and a used cover is perfectly
fine.
Thanks,
Taylor
******** END ********

Yes, it will likely cost $1$$$. But I'm very impressed by Taylor and I'm very confident in his ability to make this 100% right.

Mrmerlin

good, glad you got it towed , it sounds like your machine is in good hands

heinrich

LOTS of mis-information here.

1) your pump and centre cover are what they are, YOU NEED THE RIGHT PARTS. They are still available for every model produced. DO NOT UPDATE. The pump and cover for different years go with your tensioner, and must be the right part, not a later part. Water pumps and centre belt covers were not superseded. Btw check the tensioner part number as well to ensure you have the right part, as well as idler roller and arm.

2) A mechanic needs to pull the tensioner and disassemble it properly and not "toss oil in there and see if it leaks"

3) Pivot bolts do not work themselves loose. And they CANNOT crack the cover. If they are loose, it is because someone didn't instal it properly. DANGER: often the wrong tensioner will cause rubbing on the centre belt cover. This needs to be corrected to make SURE you have the right parts for your engine year. This is more likely why your cover is cracked.

4) Cam timing: Huh?? How is it correct now but wasn't going to be for much longer??

5) It is possible (and likely) that someone installed a mish-mash of older and newer parts. This WILL cause belt failure.

Bill Ball

I'm not as convinced as Heinrich that there is any significant misinformation, rather just what happens when people try to summarize things in an email. For example, in Heinrich's point number 4:

4) Cam timing: Huh?? How is it correct now but wasn't going to be for much longer??

The shoulder bolt or stud, whichever it might be, had just about come off, if I am interpreting correctly. Had it gone a little further out, this would have allowed the belt to get significantly loose, if not come off, which could allow the belt to skip teeth or come off. That would certainly change the timing.

See what I mean?

You can argue as to whether the tensioner needs to come off and be completely rebuilt or whether he takes the route the mechanic is taking. That's not necessarily misinformation at all. I could go on, but I think there is enough in his reply for me to feel the mechanic probably knows what he is doing (at least as much as I do), allowing for some literary license due to the fact this is an email as well as difference in opinion about how this should be fixed.

There's always room for debate about this or that approach. It's not ALL in the manual. He notes you have a new "leakproof" pan gasket. My interpretation is he means someone installed one of the aftermarket silicone gaskets. That's not a Porsche part. I have very mixed feeling about those gaskets. They can leak. And they cannot be snugged down once that happens as they do not tolerate much torque. I've seen them "squeeze" out, especially once the gasket leaks and the surfaces get coated with oil. The silicone gasket is very slippery and does not form to the pan cutouts like the more compressible cork gasket. Yet, many knowledgeable people here LOVE the new silicone gaskets and would not install the OLD style Porsche cork gasket ever. Properly installed (squeaky clean and dry surfaces, proper low torque, bolts sealed so thay cannot back off) with some luck that none of the bolts ever back off, the silicone gasket should not leak and should outlast the cork gasket, but.... See the problem? You know what the say about opinions...

Mrmerlin

well fellas I wouldnt get too spun up about the diagnosis and resultant report.

Since to me it sounds like the owner is only paraphrasing what he was told.
And isnt a seasoned 928 mechanic a subtle if , and, but, or whatever can change the whole meaning of something that we might have a better understanding on

It is quite possible for the cover to get damaged by a loose pivot bolt, usually with a loose bolt you find it does in fact contact the cover,
same goes for a slipping WP pulley the hub will rub if its been slipping out of the bore
needless to say the car sounds to me as if its in good hands compared to the owner trying to diagnose his cars problems