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Ug, I say, ug. After getting 4 nice new snow tires on the 86.5 928, after finally adjusting the transmission to the point where it shifts like a dream, and on the last weekend before it gets cold and miserable till March I was driving the car home from a short trip and the dreaded Belt Ten light came on.
Belt does have a good 60k miles on it, and yes it's time to replace. Last adjusted the tension 2 years and 20k miles ago, not sure if a retension is enough. Since it's winter, anyone know of a good shop in the MD area that can just to it? I do not think I want to be out there in the cold trying to apply 200+ foot pounds of torque to loosen the main pulley bolt.....
You know these cars. It's not as much about the belt as it is deciding and sourcing of the ancillary parts.
Do you want to do the whole shebang, parts bought upfront before teardown, Wp, tensioner kit, pulleys, possibly cam and oil pump gears, o rings and seals? If you go that route, meaning the car wont be occupying garage space waiting for parts decisions and sourcing, then bring it down 95 to ladysmith. You and I can attack it. One long day. ( Well, wife just nixed that offer covid fear / comorbidity )
There is an independent in rockville that I know has replaced some, nice older guy and daughter. But in casual conversation they really weren't knowledgeable like us rennlisters.
All that said, I've retensioned them multiple times, even on highway. But I knew my water pump was good and belt still tracking well. And generally what triggered it was a violent accelleration.
Regardless of miles, I prescribe to changing the timing belt at the prescribed miles, however the maximum period I let them run for is 5 years regardless of the miles travelled. (timing belts run in a temperature variant atmosphere). I've owned my car for over 21 years and it is still fitted with the water pump I fitted just after purchase "Yes" 21 years ago" and the WP is fitted with the plastic impeller "A must in my opinion". If no water is emanating from the weep hole in the water pump the seal is OK, however if the bearing is detoriating, i use a screw driver to listen to the running bearing . At a belt change I check the end play and the run out of the WP (no need to take the water pump off the block to do this).
Seeing that the tensioner light is illuminated I would recommend getting a Kemp Gauge to check the tension or the Porsche 9201 dial indicator gauge if it will fit
At a belt change I LSO check the tensioner and other ancillaries that run off the timing belt such as the guides. oil pump, tensioner etc. As a Professional Engineer with a full workshop, I do all my own work including electrical, except the electronics. LH & EK Computers.
More damage is done when a good working unit is pulled apart, inspected and reassembled. Usually new parts fitted or old parts refitted are reassembled, this can also be where mistakes are made.
Spares are getting hard to source and when I need parts, I hit the web.
Yup. Car is apart with the engine cold/not started in 20 hours, passenger belt guard off and sitting at camshaft TDC with crank at TDC mark. Now that I bought my kid their Super Smash brothers DLC I'll go out and measure it with the freshly penetrating oiled and wiped off Kempf tester.
Landseer, that is probably the best offer in the universe but can't take advantage of it due to COVID. Next summer sure!
Let's see what we got here. Loose wire? Or doooooom!
Hm. First check was just moving the engine to TDC, rotor at TDC and it was at dead center. Which would mean a bit loose.
However I pulled the car through two crank rotations, getting it right on TDC 0 at the crank shows the pointer is closer to the front of the engine, not *quite* proper tension but close. TDC 0 at crank. TDC 0 at camshaft Money shot of Kempf tensioner at the point where it goes *tink* as it hits the back of the belt cover.
(Handy hint: Putting a dab of red paint on the front of the pulley right where the lower front belt exits it at 0 degrees makes it a LOT easier to turn the crank from the bottom which is the only way to do it)
I looked up my old thread on this, it was from 8/25/2017 so over 3 years ago not two...
Back then when I checked the Kempf tool showed in the center. However according to FredR, you do kind of need the pointer it right at the front edge of the window on a 32v engine and not dead center. To get it right I tightened the adjusting bolt 1/2 turn.
So it's been a couple of years, and might be due for a bit of an adjustment. How does going 1/4 of a turn on the tensioner bolt sound, then run the engine through 2 complete turns, then measure again?
Last edited by Christopher Zach; 11-27-2020 at 01:56 PM.
Reason: Added pics and cleaned it up a bit
Yup. Car is apart with the engine cold/not started in 20 hours, passenger belt guard off and sitting at camshaft TDC with crank at TDC mark. Now that I bought my kid their Super Smash brothers DLC I'll go out and measure it with the freshly penetrating oiled and wiped off Kempf tester.
Landseer, that is probably the best offer in the universe but can't take advantage of it due to COVID. Next summer sure!
Let's see what we got here. Loose wire? Or doooooom!
The timing belt warning exists to tell the owner to check and if necessary tighten the belt a bit. Not sure about your MY but my warning says "Timing belt service" it does not say "tough luck you have 32 bent valves". Needless to say if you have covered 60k miles on the belt then you have had your money's worth out of it and time to change it irrespective of what happened.
Did the alarm come on and stay on or did it go out after you accepted the alarm? If it went out chances are it was a spurious alarm.
The timing belt warning exists to tell the owner to check and if necessary tighten the belt a bit. Not sure about your MY but my warning says "Timing belt service" it does not say "tough luck you have 32 bent valves".
Sorry, I broke a belt (granted a -00 belt which we found had defects) on my 944S and I am always just a tad bit jumpy. Yes, the 944S runs at much higher RPMs, and yes the original -00 belts were *bad*, and yes the 928 belts are not like that, so there is that.
Needless to say if you have covered 60k miles on the belt then you have had your money's worth out of it and time to change it irrespective of what happened.
Yes, it is that time. Was hoping to do it in the spring with flowers and all that. The water pump and idlers were replaced at 60k so my initial though was belt+rebuild tensioner. Big question being getting the front bolt off (I have changed belts on the 944S, but you can sneak the belt around the pulley so it doesn't have to come off).
Did the alarm come on and stay on or did it go out after you accepted the alarm? If it went out chances are it was a spurious alarm.
My alarm accept button is spurious sometime, loose connection in there. However I did drive home, shut down, start up, and no alarm after 3m. So it's possible it was spurious.
PS: I just updated my last post BTW and will add pics of the tension. It looks ok enough, maybe a tiny bit looser than when I set it 3 years ago (pointer is between center and right of the front window as opposed to right at the edge of the front window) so I'm debating adjusting the tensioner 1/4 of a turn.
Last edited by Christopher Zach; 11-27-2020 at 01:59 PM.
Being a bit sensitive is way better than being non attentive with these things. In a way spurious alarms are a good thing in that if nothing else they suggest the belt tension alarm system is working.
With regard to the Kempf tool I have always used the mid point position but then I also wondered if ambient temperature may play a role in this. If it is close to freezing when one starts maybe that makes a difference compared to when it is say 30C ambient as is often the case in my situation. Thus following the end of the window perhaps makes sense for cooler climates or so I reasoned.
If you tend to lay the car up during the winter months then I see no reason why you have to do the thing right now. Just take a good look at the belt and see what it looks like.
Chris the belt should be tensioned to the top edge of the window on your gauge on the 32V cars,
if the pointer is at the center then its too loose.
As pointed out earlier the rotors should point to the left fender when the engine is at TDC,
and the engine should be cold when checking.
NOTE use a deep 27MM socket to turn the crank
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
The factory recommendation for belt change intervals is based on new parts and pieces. The pieces behind the belt need to be new with the belt if you want to use that number. I'm sure that Porsche had a failure-probability bell curve, and hopefully the 60k is very close to the bottom of the bell. For those of us who are not-frequent drivers, even new ball bearings suffer with age. The petroleum components in the grease evaporate slowly, leaving the wax/soap cake around the rolling elements. Can't see or feel this from the outside of the bearing, so any guesstimate of remaining life is just that.
Meanwhile, since the first belts were made, advances in materials and manufacturing now give us Kevlar (aramid) reinforcing fibers, and better rubber compounds to boot. The Gates "racing" belt has extra reinforcing molded in, and undoubtedly adds to the expected life of the belt, as there's a much less stretch and less chance of failure of the cords inside. The "teeth" benefit from the better reinforcement some too. Still, life depends on everything else being in new condition.
A belt warning is the result of wear somewhere. The belt stretches, bearings and gears wear, and that's about it. Regardless of which it is, it's a sign that something is wrong. By 60k (and likely before then for me) the belt and supporting components need to be replaced. Re-tensioning gets your car home and maybe the repair shop to get the work done.
Ok, so I went out, marked the top face of the adjuster bolt with red paint, waited 30 minutes for it to dry, then loosened the adjuster lock nut, turned the bolt exactly 90 degrees clockwise, locked it down, and checked tension. Now it's right on the edge of the window. Turned the engine 2 turns, checked again, right on the edge of the window.
Buttoned everything up and car is now back together. It looks like the stretching is linear: When I did this 3 years ago the belt was in the middle of the adjuster window and 1/2 turn took it to the edge. Now 20k miles later it was 3/4 way to the edge and a quarter turn took it to the edge of the window on the tensioner.
Car is now going to be in very limited driving mode until I get the belt replaced.
The factory recommendation for belt change intervals is based on new parts and pieces. The pieces behind the belt need to be new with the belt if you want to use that number. I'm sure that Porsche had a failure-probability bell curve, and hopefully the 60k is very close to the bottom of the bell. For those of us who are not-frequent drivers, even new ball bearings suffer with age. The petroleum components in the grease evaporate slowly, leaving the wax/soap cake around the rolling elements. Can't see or feel this from the outside of the bearing, so any guesstimate of remaining life is just that.
Yup, I checked the papers and the first belt change was done at 70k along with new rollers and water pump. I got it at 103k or so and the belt tripped the alarm at 105k which resulted in my last freakout. It's now got exactly 129,087 miles meaning there is a good 59.1k miles on this belt. I've followed the schedule of retensioning the 944S at 2,500, 15,000, 30,000, 45,000 and replacing at 60k. So tensioning intervals on this one were 0, 35k, 25k. Question: Does everyone check tension on their 928S belts at about the same interval, or when the light goes off?
Meanwhile, since the first belts were made, advances in materials and manufacturing now give us Kevlar (aramid) reinforcing fibers, and better rubber compounds to boot. The Gates "racing" belt has extra reinforcing molded in, and undoubtedly adds to the expected life of the belt, as there's a much less stretch and less chance of failure of the cords inside. The "teeth" benefit from the better reinforcement some too. Still, life depends on everything else being in new condition.
True, I had very bad luck with the first gen 944S belts, but to be honest I haven't heard of anyone breaking a belt since they came out with the -02 version. Also the 928 cruises at 60mph at 2k RPM instead of the 3k for the S, and tends not to run at high revs much.
A belt warning is the result of wear somewhere. The belt stretches, bearings and gears wear, and that's about it. Regardless of which it is, it's a sign that something is wrong. By 60k (and likely before then for me) the belt and supporting components need to be replaced. Re-tensioning gets your car home and maybe the repair shop to get the work done.
Ok. I always thought that the belt would stretch a bit during its normal life, thus the retensioning intervals.
Meantime car is on a driving diet. I'll check around to see who can do replacements on it and decide if I want to just park it till spring and a 3/4 breaker bar+27mm socket finds its way into my life or send it off to be done.
Hm. First check was just moving the engine to TDC, rotor at TDC and it was at dead center. Which would mean a bit loose.
However I pulled the car through two crank rotations, getting it right on TDC 0 at the crank shows the pointer is closer to the front of the engine, not *quite* proper tension but close. TDC 0 at crank. TDC 0 at camshaft Money shot of Kempf tensioner at the point where it goes *tink* as it hits the back of the belt cover.
(Handy hint: Putting a dab of red paint on the front of the pulley right where the lower front belt exits it at 0 degrees makes it a LOT easier to turn the crank from the bottom which is the only way to do it)
I looked up my old thread on this, it was from 8/25/2017 so over 3 years ago not two...
Back then when I checked the Kempf tool showed in the center. However according to FredR, you do kind of need the pointer it right at the front edge of the window on a 32v engine and not dead center. To get it right I tightened the adjusting bolt 1/2 turn.
So it's been a couple of years, and might be due for a bit of an adjustment. How does going 1/4 of a turn on the tensioner bolt sound, then run the engine through 2 complete turns, then measure again?
While I say that 60,000 miles is "my limit" for belt use, in looking closely at your pictures (from what I can see), your belt seems to be in nice condition.
And the amount of time since you replaced it is certainly in your favor.
The downside is that I never expect to have to re-adjust a factory timing belt, after the first 30,000 miles. They seem to stretch and then stop stretching.
(Truthfully, I have zero experience with other than factory belts, so I can not judge how much aftermarket belts continue to stretch, if that is what you used.)
Additionally, the amount that you needed to tighten the belt, to get it adjusted, does not seem all that extreme.
What have you got to loose?
At 132,000 miles, the exhaust valve guides are toast and the stem seals are cooked.
And after 35 years, the head gaskets are probably trash, from soaking in coolant.
If the belt breaks, it's not the end of the world....
Just an opportunity to "freshen" more stuff.
11-26-2020, 04:21 PM
*UG* Timing belt light came on, great.....
