Jump to content


Photo
- - - - -

Rear Main Bearing Seems To Have Failed


  • Please log in to reply
16 replies to this topic

#1 alpder

alpder

    Mini Mad

  • TMF+ Member
  • PipPipPipPip
  • 144 posts
  • Location: Pembrokeshire
  • Local Club: MCR

Posted 01 April 2024 - 09:50 PM

Clutch started slipping today.

Quick look underneath sees a drop of oil on the jiggle-pin on the housing.

So off with clutch cover. Expecting to find oil.

And indeed there was some in there. But more, errm, "interestingly"... when I rotated the engine by hand, I could hear a quiet, but very very wrong, grinding sound.

Which turned out to be the teeth on the flywheel just beginning to scrape on the bottom of the clutch housing.

So, the cause of the oil seal failure seems to be that the crankshaft has dropped at the clutch end. Which is, obviously, real bad Bruce.

 

I wonder how long it would have carried on running, and how big a bang it would have finally failed with, if the oil leak hadn't caused the clutch to slip and prompted an examination.

 

Out with the subframe tomorrow for a better look and a strip-down. But, clearly, it's going to be £ugly£. Only 600 miles on the engine, too. I must have c*cked-up the rebuild, somehow. Tomorrow we'll see how much is salvageable.

 

:-(

 



#2 Earwax

Earwax

    Speeding Along Now

  • TMF+ Member
  • PipPipPipPipPip
  • 424 posts
  • Location: Brisbane

Posted 02 April 2024 - 12:19 AM

I would not go totally wild on the strip down straight off.  Just thinking about possible other things causing noises ....... many of these are probably laughable or impossible etc , but just throwing out some ideas.

 

the flywheel creeping up the taper may alter clearances

the flywheel having popped off the taper but a burr is stopped it from freeing altogether

the starter not fully disengaging

the flywheel ring somehow

the backplate bolts are too long (just) 

incorrect transfer case gasket thickness???

 

This is probably worth a couple of sets of eyes looking over things with a beer in hand until you are very sure of what has transpired. Good luck and i hope it is not too ugly a fix



#3 DeadSquare

DeadSquare

    Up Into Fourth

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 2,743 posts
  • Location: Herefordshire
  • Local Club: Unipower GT Owners Club

Posted 02 April 2024 - 07:56 AM

Loose main bearing bolts or cracked rear main cap.



#4 sonscar

sonscar

    Up Into Fourth

  • Members
  • PipPipPipPipPipPipPipPipPip
  • 2,714 posts
  • Location: crowle
  • Local Club: none

Posted 02 April 2024 - 08:08 AM

Surely for it to move so far the crank must be bent or broken?or all three lower main ratings completely missing?Explore earwax offers closely first.Steve..

#5 KTS

KTS

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,250 posts
  • Location: Herts

Posted 02 April 2024 - 08:33 AM

..if there's any issues with the engine itself i would expect that to be evident when you drain the oil 



#6 alpder

alpder

    Mini Mad

  • TMF+ Member
  • PipPipPipPip
  • 144 posts
  • Location: Pembrokeshire
  • Local Club: MCR

Posted 02 April 2024 - 10:16 AM

..if there's any issues with the engine itself i would expect that to be evident when you drain the oil 

Yep. Splinters big enough to spike my finger, when I ran it along the sump plug magnet this morning.



#7 Cooperman

Cooperman

    Uncle Cooperman, Voted Mr TMF 2011

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPipPip
  • 23,029 posts
  • Location: Cambs.
  • Local Club: MCR, HAMOC, Chelmsford M.C.

Posted 02 April 2024 - 10:25 AM

Unlikely to be a main bearing issue.
First of all with the engine still in the car, remove the clutch and flywheel.
Then you can check for axial movement of the crankshaft end. If the crank end moves enough for the flywheel to hit the casing, I would suspect a snapped crankshaft.
Why would you take the sub-frame out to check the engine? That's a very hard way to do things. Just lift the engine and gearbox out from the sub-frame.

#8 KTS

KTS

    Up Into Fourth

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPip
  • 2,250 posts
  • Location: Herts

Posted 02 April 2024 - 10:33 AM

 

..if there's any issues with the engine itself i would expect that to be evident when you drain the oil 

Yep. Splinters big enough to spike my finger, when I ran it along the sump plug magnet this morning.

 

 

full teardown (including the gearbox) would seem the only sensible approach; good luck !



#9 Cooperman

Cooperman

    Uncle Cooperman, Voted Mr TMF 2011

  • TMF+ Member
  • PipPipPipPipPipPipPipPipPipPipPip
  • 23,029 posts
  • Location: Cambs.
  • Local Club: MCR, HAMOC, Chelmsford M.C.

Posted 02 April 2024 - 12:29 PM



..if there's any issues with the engine itself i would expect that to be evident when you drain the oil

Yep. Splinters big enough to spike my finger, when I ran it along the sump plug magnet this morning.

full teardown (including the gearbox) would seem the only sensible approach; good luck !

That would seem to be the only sending answer now.

#10 alpder

alpder

    Mini Mad

  • TMF+ Member
  • PipPipPipPip
  • 144 posts
  • Location: Pembrokeshire
  • Local Club: MCR

Posted 03 April 2024 - 04:43 PM

The source of the metal. Or, at least, a source of the metal...

 

Attached File  IMG_20240403_165343.jpg   120.86K   4 downloads

 

Attached File  IMG_20240403_165410.jpg   55.83K   1 downloads

 

The high-point on the timing cover is (was) a dimple pressed into the metal to clear the old SPI pickup. Fine for the original simplex chain. But just fouls a duplex.

 

Don't yet have the engine/gearbox split: waiting for MS delivery of the driveshaft removal tool. Despite being a newly built engine, those pot-joints are just not going to release with Haynes's "careful use of a pair of levers". I even experimented with careless use, but no joy.

 

Edit: Just found this description of a repro of this same cover on MiniSpares website: "Timing cover for single point injection cars only with bracket on. This has the flattened type breather canister for clearance also. If fitting with duplex timing gears the metal indent by the oil seal will need tapping out to stop fouling on the chain."

 


Edited by alpder, 03 April 2024 - 08:09 PM.


#11 Designer

Designer

    Speeding Along Now

  • TMF+ Member
  • PipPipPipPipPip
  • 328 posts
  • Location: Surrey
  • Local Club: LSMOC

Posted 04 April 2024 - 06:45 AM

Despite being a newly built engine, those pot-joints are just not going to release with Haynes's "careful use of a pair of levers". I even experimented with careless use, but no joy.

 

 

Are the pot-joints new ones. I replaced ours sometime back and I have never been able to remove them, even with the special tool. 

There is a post on here that I seem to remember says that due to a different groove machined the circlip ring on the end of the drive shaft will not slide out of the groove in the pot-joint. To get around this problem one has to turn the shaft a couple of degrees tap the shaft or pot-joint. Then try removing the joint if this does not work turn the shaft around another couple of degrees, and repeat until successful. The idea of this is to make sure that the circlip ring is positioned evenly around its groove and has not dropped to its lowest position. Once it is central they pot-joint should come off.

I have not done this as when I have needed to remove the engine since changing the pot-joints I have just separated them and fitted new large boot clips.



#12 Lplus

Lplus

    Super Mini Mad

  • Members
  • PipPipPipPipPipPip
  • 537 posts
  • Location: Hampshire

Posted 04 April 2024 - 10:50 AM

Despite being a newly built engine, those pot-joints are just not going to release with Haynes's "careful use of a pair of levers". I even experimented with careless use, but no joy.

 

 

Are the pot-joints new ones. I replaced ours sometime back and I have never been able to remove them, even with the special tool. 

There is a post on here that I seem to remember says that due to a different groove machined the circlip ring on the end of the drive shaft will not slide out of the groove in the pot-joint. To get around this problem one has to turn the shaft a couple of degrees tap the shaft or pot-joint. Then try removing the joint if this does not work turn the shaft around another couple of degrees, and repeat until successful. The idea of this is to make sure that the circlip ring is positioned evenly around its groove and has not dropped to its lowest position. Once it is central they pot-joint should come off.

I have not done this as when I have needed to remove the engine since changing the pot-joints I have just separated them and fitted new large boot clips.

I do recall the problem being mentioned in the past, but it may have been in a magazine.  I seem to recall the person had to cut the pot joint apart to get it off.  As you state, the groove inside the pot joint for the circlip to drop into was not shaped correctly so that the circlip would be compressed when the joint was pulled to remove it.

 

That was a few years ago though and the set of pot joints I bought in the last year or so were fine for removal.



#13 alpder

alpder

    Mini Mad

  • TMF+ Member
  • PipPipPipPip
  • 144 posts
  • Location: Pembrokeshire
  • Local Club: MCR

Posted 04 April 2024 - 10:54 AM

D'oh... should've thought to do it this way from the start. Two quick taps on a tang-thru screwdriver and the driveshafts are off...

 

Attached File  IMG_20240404_114507.jpg   43.23K   2 downloads



#14 alpder

alpder

    Mini Mad

  • TMF+ Member
  • PipPipPipPip
  • 144 posts
  • Location: Pembrokeshire
  • Local Club: MCR

Posted 04 April 2024 - 04:06 PM

Thanks to all for their input.

 

The findings so far:

 

There's oil on the clutch. And a little clean oil on the output-gear splines. So the source is probably in this area. No sign of oil running down the back of the tx case though, so doubtful that it's the clutch oil seal.

 

As others have predicted the main bearings seem fine. No discernible crankshaft movement or end-float. But there is a shiny new witness-mark on the tx-case where the flywheel has eroded it. I can't remember the order of disassembly... but if I loosened the pressure-plate from the flywheel and *then* turned the engine, that would account for it, and for the nasty noise. Maybe I did. Wish I could remember. I'm going with this theory (i.e. that I'm an idiot) for the time being.

 

The clutch oil-seal appears entirely undamaged.There is a mystery with this particular clutch oil-seal in that fitting guides say to sheath the output splines when fitting the seal, to prevent damaging the seal when it is passed over them. But the output splines are about 0.8mm smaller dia than the oil-seal - so they won't harm it anyway. Is this normal? The seal appears to be the correct one (70/55/10 in Viton), is nearly new, and has a direction arrow which matches the engine rotation. I'll change it anyway.

 

There is some slop (cheapie dial gauge says 0.12mm sideways movement - 5 thou) on the output-gear bushes. And that feels like a lot but I have no knowledge of what it should be. Maybe the oil is escaping that way - between bush and crank. OTOH the gear is a brand new (A+/A hybrid type) and the crank isn't significantly marked... so where has the slop come from? I'll start another thread about it, with measurements.

 

As for the metal shards... it does look like the magnet has gathered most of it. Certainly no visible lumps in the gearbox and all the bearings that have come apart so far have no sign of scoring. Bores are clean too. And the oil isn't sparkly. Worry-rating reduced from a "9.5" to a "7". For now :-)



#15 Spider

Spider

    Moved Into The Garage

  • Admin
  • PipPipPipPipPipPipPipPipPipPipPip
  • 13,873 posts
  • Location: NSW
  • Local Club: South Australian Moke Club

Posted 04 April 2024 - 05:12 PM

D'oh... should've thought to do it this way from the start. Two quick taps on a tang-thru screwdriver and the driveshafts are off...

 

 

For what ever it's worth, that's how I do them. Usually easy and clean :proud:

 

I've posted a reply in your primary gear thread.
 






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users