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@depami I agree with you. I'd think the dial shouldn't flex back. Either direction I pry, the gauge goes back to zero. With movement, the dial reading would remain static.
I have no issues digging deeper into the 928. I suppose best course of action would be to get the timing belt back on. Get the pinch bolts tightened down. Start-up again and see if the screeching has subsided. From there, drop the oil pan...
Is the dial showing movement or flex? If movement, shouldn't it stay at each extreme?
It's a lot of work, but, removing the oil pan would expose the thrust bearing.
That is a good point. The crank should be static at both extremes unless something else is causing a spring type reaction pushing the crank back. On the other hand the dial gauge is measuring a realistic movement.
Whatever is causing this to happen may well be the source of Jake's screeching problem.- buggered if I can suggest what it might be at the moment.
If you can’t detect a small amount of play back-and-forth without prying, very hard on the fly wheel then there’s a good chance that the thrust bearing has been damaged to the point that it’s taking up the clearance that should be there. A check of the dipstick oil would be prudent right now on some black cardboard and look in the sun. If the oils got a bunch of metal in it, then you know that your engines making metal.
@Mrmerlin I changed the oil and filter that was original to the vehicle before I started the engine- as it was low on the dipstick.
When I did check the pre-oil-change oil, I did look closely to see if there was any metal shavings (I couldn’t see any… that was also a reason why I went with this project 928). The old oil was used, but not dark black.
I’ve run the new oil for maybe less than 3 minutes and I do not see any glittery specs when held up to the sunlight on a dark square of paper.
I suppose we are all in agreement that the next logical step is to drop the oil pan?
is it hard to turn the engine over by hand?
can you compare it to another 928?
I would put it back together and run it for a while to see if its making metal,
at this point you dont have much to loose if it is
Although probably not of relevance I just noticed that the torque tube fitted is the later model 28mm tapered shaft with two bearings that was introduced on the late 87 S4 models there or therebouts..That suggests some drive line trauma and you say the car sat idle for many years - could there be a connection?
While you ran the engine with the accessory belts removed, were you able to check the bearing highlighted in the picture? Even if new, it can make quite a lot of high pitched noise if it is coming in contact with the timing belt. You will likely need to check this from beneath the car as it is difficult to see with the dampener installed.
I would be inclined to verify this before dropping the oil pan. Mr Merlin has mentioned metal in the oil and you have indicated there is none evident to which he suggests getting the engine running again. FredR has indicated that this type of noise is not generally associated with TBF. If you can at least get the car driveable for a while, you will be better able to identify and prioritize other jobs to be tackled.
@Mrmerlin Yes, this 928 is more difficult to turn by hand than my 944... but I wouldn't say doubly as hard. It takes effort, but not anything that would instantly alarm me. I appreciate your logic with getting the engine back together to see if metal is being made! No loss to me if the thrust bearing is indeed worn beyond spec.
@FredR - Thanks for this tip! This 928 is very original and complete. As far as I can tell, it was always serviced by someone who knew these vehicles well- all oem nuts, bolts, and hardware. I was surprised to find an exhaust bracket missing (see post #11 on this thread). The Carfax report is absent of service history records. While removing the interior rear seats, I did find glass- likely from a smashed rear passenger quarter panel window. The rear passenger quarter panel also has a small dent... but nothing significant. No other damage to report.
If you still have the old oil filter you might want to cut it open and have a look. You bought it as a non runner and it sat for 25 years. So the flex plate migration has loaded the crank for a long time. Who knows how long it had been driven in that condition. The crankshaft and thrust bearing could be so damaged it can't move.
I tried my hand at prying at the flywheel and I finally got it to loosen. I am now hearing the "thunk". I believe according to my dial gauge I'm getting a consistent reading of 0.05" or greater than 1.2mm of play!!! Here is a short video clip showing the reading as a pry.
07-15-2023, 08:51 AM
