Bonecrusher

i think i just experienced a flex plate issue

Bonecrusher

1988 Porsche 928 S4- the brakes were locking up --long story --but finally replaced the master cylinder and i think the brakes are fixed, but this resulted in driving the car with the brakes on and putting the drive line under great stress. Then the car was difficult to get to turn over and start but then would die after warmed up. now at the point where i can crank the engine only with a breaker bar and will not turn over with the starter. now i realize i think i have met the dreaded flexplate issue. i am going to release the TT this afternoon. is my engine dust is the question ??

davek9

You need to remove the lower Bell housing and disconnect the TT from the Engine, mark it so you can put it back in the same spot.

Before you unbolt the TT pinch bolt look and see if the Flex plate is con-caved towards the flywheel, mark the spline and measure it, before and after releasing the pressure if there is any.

Many write-ups here on the issue, with pic's.

Bonecrusher

thanks pass the popcorn

FredR

Are you sure your battery is ok? Is your ground strap at the battery in good condition?

If the engine had seized due to molten white metal you would not be able to crank the motor with anything.

If you know about TBF did you take any precautions to mitigate such? Have you previously checked for migration of the clamp and do you know what the crank end float is?

Things to do before releasing the clamp:

1. Take some photos and post them to show where the flex plate clamp sits.
2. Look at the flex plate blades and see if they look physically deformed [i.e. not straight].
3. Put some indexing marks with paint or tippex on the shaft where it enters/leaves the clamp.
4. Consider that flex plate issues can be caused by the rear clamp slipping as well as the front clamp so pulling the rear bolt, inspecting it and replacing it from time to time is also important.
5. If then undo the bolt on the front flex platemany examples will jump a couple of mm and whereas this is not what is wanted such is not usually harmful. If jumps a bunch more than you may well have issues.

Way too early to start speculating about whether the motor is damaged.

Mrmerlin

a quick test,
pull the dipstick out,
then put some lamp cord down the tube,
then pull it out,
drip the oil onto some black cardboard,
look at the oil in the sun.

if you see lots of metallic s then your engine is probably grinding to a halt on the thrust bearing
NOTE the reason not to use the dipstick for the oil sample is that,
every time it rides the tube, it shears off a small amount of metal,
and this could change the result

Imo000

Probably.

Mongo

Complete engine shopping at 928 International would be a good start right about now.

Bonecrusher

thanks for the responses
i just bought the 928 six weeks ago although i had a picture of one on my wall as a teenager.
i had never heard of the flex plate issue before but it is making me wish i stuck with the poster on the wall. the car only has 63k miles so i am asking myself what did i do wrong.?
at this point the engine turns over and wants to start when cold
i inspected the flex plate and it looks flexed.
i cannot detect any motion on the flywheel but i need the micrometer.
when i loosened the collar bolt, the tube seemed to back off a few millimeters. there were signs of some motion wear on the rusted splines see attahced picture
are there any other hidden gremlins in my new 928 ?
save it or sell it is the question now ????

Bonecrusher

"Way too early to start speculating about whether the motor is damaged."

tried to check the dip stick ---it seems fine
pulled plugs --they all seem fine
will drop oil on black cardboard
any other tests before Waterloo ??

FredR

I take it the photo is in the condition it was before you released the pinch bolt. You have the early type drive shaft [generally a good thing]- I understand it was fitted to the early S4 models. To my eye that shaft looks well down the splines [i.e. as in it has slipped] but whether that position is typical with the earlier shaft I do not really know.

On the photo you can see some polished surfaces along the splines suggesting slippage. Unfortunately you did not follow the advice to make some indexing mark so I cannot tell how far it will have moved.

When the bolt was released do the leaves of the flex plate appear to be perpendicular to the shaft axis or do they appear to be perrmanently bent? Either way your next step is to determine the crank end float- the centre main bearing of the crankshaft also contains an integral thrust bearing to control axial movement. The end float in a good engine will be about 0.2mm and according to Porsche replacement of the thrust bearing is required when end float is 0.4mm. To measure this you really need a dial gauge on the fly wheel and then pry the crank forwards/backwards to determine the state of play.

You have done nothing wrong at all. Way too many S4's/GTS automatics suffer from this phenomena and many owners have lost out big time as a result. There are several solutions to stop this problem but let's find out exactly where you stand. Mileage is not an indicator- indeed many examples start to have issues with very low miles on the clock. Some foks buy these car thinking that they cannot go wrong with a low mileage example, some buy them from previous owners who know there is something wrong and just want to get rid of them- hopefully not the case here but...? Ironically low mileage examples seem to suffer from more issues probably because the time based servicing required is not carried out so a good service history is everything with these cars. For instance the coolant needs changing every two years irrespective of whether used or not as does the brake fluid.

Mrmerlin

umm what does it mean you tried to check the dipstick?

what I was suggesting is to get some wire and slide it down the dipstick tube to get an oil sample ,
this is the easiest thing you can do to determine where to go next,
it involves no tools .

usually removing the preload from the engine will then permit it to run normally,
BUT lets get an oil sample first

Bonecrusher

riddle me this batman ........ i have tried to measure the end play and cannot get it to move more than .003 inch. does the thing not move after you have welded it into the block ?
here is the oil filter ----
and i did mark the flex plate .
if these are such great cars why am i losing sleep over this thing ?????

Bonecrusher

here is the flex plate and oil filter pics

Mrmerlin

Ok so you removed the pinch bolt,
what does the engine do now?
will it run?
In the picture of the oil filter just to confirm are all metal pieces?
did you put a dial gauge on the flywheel and pry it front to back?