algie928s4

Not much of a mechanic myself, monkey see - monkey do is the best description, so a mate with a 928S4 shows me the maintanance procedures and I take it from there, today was checking the timing belt tension after replacing the water pump a 1000 miles or so ago, monkey didn't see he just did, cost me two, YES two radiators, a series of comical yet unfunny incidents that could only happen to this monkey.
Anyway we checked the flex plate today, 4.5 millimeters of movement when the pinch bolt was slackened, and from memory the Rennlist suggests this is when the problems will come to light after releasing the pressure, so the two questions are:-
1- How long will it take for any damage to come to light.?
2- Is this an unwanted record?
Oh and if the two radiators beggars belief, it's the THIRD radiator in less than a year!, the car had a leak when purchased!!!!!!

shaaark89

the movement of the flexplate is not what's critical as most of them will move a good amount when released. the issue is whether the pressure has caused any thrust bearing wear or worse yet wear into the block. this can be measured by measuring end play in the crank itself by prying the flywheel forward and back and measuring the travel with a dial indicator. don't remember offhand what the wear limit is, but hopefully someone will chime in there.
thrust bearing failure will manifest itself with difficulty cranking the engine especially when hot to the point where the engine will not turn. metal shavings in the oil is an ominous sign as well.

jserio

Algie, you are no record holder thats for sure. I had my flexplate checked last June ( do for another) and that bad boy sucked out over an inch and I have a witness. The thrust bearing was checked as Tom described. That was 15k miles ago with moderate to somewhat hard driving. Not saying this is or isn't damage to your engine but odds are there isn't. 4.5 mm is not much that I would worry about. Only if nothing was done about it but you took care of that. Major important that is was retorqued to spec.

Garth S

The crankshaft end float wear limit is 0.016" ( 0.4mm) IIRC.
My flex plate retreated 3.15mm when done - and by reading of other reported cases, that is close to the norm: 4.5mm is quite a bit - but as Tom says, the true indicator is the end float measure: if that is OK, pat yourself on the back for catching the flex plate when you did - and save those pennies for the next rad.

Joe, 1" (25.4mm)!! that's huge - I wouldn't think it could move that far without failing at the fingers or bolt holes ... look for signs of metal fatigue when next in there.

jserio

Greg from Precision was the one who checked it. He made a thorough inspection and said it was okay. I was so lucky to have it checked.

algie928s4

Never one not to ask a silly question, but when I re-tightened the pinch bolt I went for as as tight as possible, my logic was the tighter the better, in the hope of reducing any future movement, could this be dangerous?
From the top of my head I think the torque is 66, I went over.
Thanks for the replies!

crackerfeet

I believe I read hat porsche's reccomended torque fix for the problem was 10% over the original stated torque which if I recall correctly is 59 lbs so 66 is where you should be.

Garth S

Ah ... how far over? That is a fairly stout bolt, grade 8 or 11.3 - but if stretched (torqued) past the elastic limit, it becomes plastic = no residual torque. You are probably OK, but regardless on the torque applied, it would seem that the clamp design is deficient. Plan on revisiting this area yearly for a measure/release episode.

IcemanG17

This is one area on later automatic 928's that must be address on a frequent basis....a little bit of work once a year will save you some serious $$$ and heartache down the road! There is an improved clamp out there, but you need to pull the torque tube to install it!
Brian