Thrust bearing failure?
10-28-2015, 01:49 PM
#16
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This morning I pulled the plugs,timing covers and belt,Engine is froze will not turn at all oil pump turns fine, cams not froze.When I removed TT I noticed flex plate was pushed forward and when I replaced TT I adjusted to proper specs.engine ran good till it seized.Kevin who is Rich VM I am interested in engine for sale ,I thank everyone for there help! Rob.
10-28-2015, 02:40 PM
#17
Rennlist Member
Not a good idea to turn the cams with the belt removed on a 32 valve motor unless you want to add bent valves to your grief list- 32 valve motors are interference engines- i.e. if the crank and valve train are out of sync they will clatter valves on pistons. You can usually get away with a small amount of differential movement and of course it only takes a small movement to ascertain the cams are not seized.
How much movement did you see when the tension on the flexplate pinch bolt was removed? A couple of mm does not usually cause any harm but if you could see the flexplate was physically distorted then that would not be a good sign.
It is starting to sound as though some damage may have been done at that time. If you used the same flexplate to clamp the TT then the chances are it slipped once more and finished off the motor. It may already have been too late by then so do not beat yourself up over it but any flex plate that is slipping has to have the clamp modified to give more grip be it by a new Superclamp or by utilising one of the additional reinforcing measures generally recognised.
If you cannot get the cams back to where they were before you removed the timing belt I would remove the cams altogether to avoid the possibility of valve damage.
Rgds
Fred
How much movement did you see when the tension on the flexplate pinch bolt was removed? A couple of mm does not usually cause any harm but if you could see the flexplate was physically distorted then that would not be a good sign.
It is starting to sound as though some damage may have been done at that time. If you used the same flexplate to clamp the TT then the chances are it slipped once more and finished off the motor. It may already have been too late by then so do not beat yourself up over it but any flex plate that is slipping has to have the clamp modified to give more grip be it by a new Superclamp or by utilising one of the additional reinforcing measures generally recognised.
If you cannot get the cams back to where they were before you removed the timing belt I would remove the cams altogether to avoid the possibility of valve damage.
Rgds
Fred
10-28-2015, 02:46 PM
#18
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Jeff,
I think I would have to respectfully disagree with yourself and SMT on this one- the cases of TBF I have been involved with suggest one of the first indicators for those not too knowledgeable of the problem is when an engine does in fact seize up - happened to my PO and a couple of other chaps over here a few years ago.
That there were potential indicators often goes amiss but owners quite often are not aware of the degradation going on [nothing has changed in the combustion process] but there is more braking resistance on the crank that sad to say is not noticed or acted upon - so it comes as something of a surprise when one day "motor no crank" but coincidentally we often read of the term "running a bit rough". To get the original motor from my current 928 to spin the local agents had to be massively brutal to break the seized white metal. The motor ran but when I got hold of it it felt as "rough as a badger's ***" [that's pretty rough!].
Of course I knew what the problem was [as did the local agents] and within a few minutes of getting the car on a lift I did not even need the dial gauge to tell me the motor was toast- which it was with 1.3mm of crank end float.
Before jumping to all kinds of conclusions though perhaps the OP can confirm his model is an automatic. Not sure if the problem was endemic in the 86 auto but maybe it is an early 87 S4?
The metal in the oil and the seized crank scream TBF but the OP needs to positively confirm such- drop the cover at the front bell housing and see if there are obvious signs of migration of the clamp along the shaft by undoing the pinch bolt as see if goes "boing".
Rgds
Fred
I think I would have to respectfully disagree with yourself and SMT on this one- the cases of TBF I have been involved with suggest one of the first indicators for those not too knowledgeable of the problem is when an engine does in fact seize up - happened to my PO and a couple of other chaps over here a few years ago.
That there were potential indicators often goes amiss but owners quite often are not aware of the degradation going on [nothing has changed in the combustion process] but there is more braking resistance on the crank that sad to say is not noticed or acted upon - so it comes as something of a surprise when one day "motor no crank" but coincidentally we often read of the term "running a bit rough". To get the original motor from my current 928 to spin the local agents had to be massively brutal to break the seized white metal. The motor ran but when I got hold of it it felt as "rough as a badger's ***" [that's pretty rough!].
Of course I knew what the problem was [as did the local agents] and within a few minutes of getting the car on a lift I did not even need the dial gauge to tell me the motor was toast- which it was with 1.3mm of crank end float.
Before jumping to all kinds of conclusions though perhaps the OP can confirm his model is an automatic. Not sure if the problem was endemic in the 86 auto but maybe it is an early 87 S4?
The metal in the oil and the seized crank scream TBF but the OP needs to positively confirm such- drop the cover at the front bell housing and see if there are obvious signs of migration of the clamp along the shaft by undoing the pinch bolt as see if goes "boing".
Rgds
Fred
As I was under the impression this is an S4 Auto issue that utilized the turned down Drive shaft.
Thanks,
Dave
10-28-2015, 03:18 PM
#19
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This morning I pulled the plugs,timing covers and belt,Engine is froze will not turn at all oil pump turns fine, cams not froze.When I removed TT I noticed flex plate was pushed forward and when I replaced TT I adjusted to proper specs.engine ran good till it seized.Kevin who is Rich VM I am interested in engine for sale ,I thank everyone for there help! Rob.
Richard Van Meeteren 770-309-5203.
10-28-2015, 05:03 PM
#20
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The build date is 11-85. Also when I removed the front flex plate it was very bowed forward so I replaced it with another one.It is a auto trans.I wonder if its worth fixing or to purchase another one and use mine for parts?It takes me a while to do much with heart failure.
10-28-2015, 06:26 PM
#21
Rennlist Member
My TBF S4 never locked up. Very slow cranking was the most obvious sign of a problem. I never saw any metal on the dipstick, but cutting the oil filter open showed lots of fine aluminum powder. Maybe that's the next thing to check? Very simple and will confirm major internal issues.
I also didn't think TBF was a common issue for 86's.
I also didn't think TBF was a common issue for 86's.
10-28-2015, 06:45 PM
#22
Unfortunately TBF can hit all MY autos and has even been known to hit 5-speeds on rare occasions.
10-28-2015, 08:08 PM
#23
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10-28-2015, 11:39 PM
#24
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10-29-2015, 09:38 AM
#25
Instructor
Yeah what. Taking the insurance off. Season ended
10-29-2015, 10:59 AM
#26
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10-29-2015, 11:34 AM
#27
Instructor
I have an 86 vin WPOJB0925GS860428. I paid a grand for it with the intention of either parting it out or making it a project car. It has been on my lift for a couple of months. I am in Natchez MS. I will part with it for what I have in it or continue my snail like rehab. I have the engine almost out, maybe this weekend. It was not running when I got it but it was in the neighborhood so I rescued it. I drive my 84 but wanted to investigate a 32v. Holler if you are interested.
10-29-2015, 12:51 PM
#28
Rennlist Member
I do believe I read it somewhere in the Cars documentation too.
10-29-2015, 01:26 PM
#29
Team Owner
FWIW the reason to keep your foot off the clutch is so the engine can build oil pressure, before a load is placed on the thrust bearing.
otherwise the crank will be pressed onto the thrust bearing with no oil pressure and increase the amount of wear the bearing sees.
Reducing the drag on the starter is really a non issue compared to bearing wear
otherwise the crank will be pressed onto the thrust bearing with no oil pressure and increase the amount of wear the bearing sees.
Reducing the drag on the starter is really a non issue compared to bearing wear
Last edited by Mrmerlin; 10-30-2015 at 09:55 PM.
10-29-2015, 05:24 PM
#30
Rennlist Member
yep... and that plus a few other tricks make the 928 engine can clutch last a very long time! 
can you short out that protective system on newer cars??? maybe there is a push in the clutch limit switch that i can spoof with a manual switch in a secret location. no??
FWIW the reason to keep your foot off the clutch is so the engine can build oil pressure,
otherwise the crank will be pressed onto the thrust bearing with no oil pressure and increase the amount of wear the bearing sees.
Reducing the drag on the starter is really a non issue compared to bearing wear
otherwise the crank will be pressed onto the thrust bearing with no oil pressure and increase the amount of wear the bearing sees.
Reducing the drag on the starter is really a non issue compared to bearing wear