Thread: TD5 BIG-END BEARING FAILURE

When the bolt loosens the corners of the flats get rounded and the sprocket then spins. I don't recall ever reading that a bolt has come out completely.

Graeme,
Thanks for coming in on this!
I can see what you're saying, and it just hit me that the noise I occasionally heard in the day or two before the bearing failure might have been made by the oil-pump drive sprocket partly riding over the outer end of the flat on the shaft, making a "B-R-R-R-R" noise as it did so.
But - another question!
Do you know what is the length of the flat section of the oil-pump drive shaft (outside the pump front cover), and the (front-to-back) length of flat section in the sprocket hub?
It seems to me that the bolt would have to unwind by about / almost the lesser of those two, in order to be able to do as you describe.
Seems like a retaining tab or split pin on the bolt would be a good idea.
Cheers, Andrew

I haven't seen a slipped TD5 oil pump sprocket/shaft and with having had 2 TD5 D2s I'm thankful that I didn't, although I replaced the bolt in the 2nd one very early when I became aware of the potential problem. However the bolt only needs to be loose enough for the sprocket to no longer be clamped for the wear to begin. If your sprocket was loose and has spun then it will be very obvious from the sprocket and shaft.

What year and how many km on the engine? This must be one of the last to fail...

Concerning the oil viscosity used: when I changed engine oil, I used Castrol Magnatec 10W-40. About 2 months later, I had the oil-cooler/warmer modified and the engine oil was replaced by the workshop, which told me that I should have used 5W-40. So I presume that at the time of the B-EB failure, and for the month before, the oil was 5W-40 (the workshop specified Penrite)

what about engine oil levels?
any chance it may seem to has risen slightly

Originally Posted by AndrewMilne

Hi Strangy,
I've thought a bit more about this and looked at pictures of the oil pump in my Haynes manual. The drive sprocket for the oil pump has a flat in the centre hole that engages with a flat on the oil-pump drive shaft. The drive sprocket is held onto the shaft by a bolt, and a chain drives the sprocket (not the timing chain as I first though it might be, but a separate one). It seems to me that the bolt would have to be very loose for the chain & sprocket not to turn the oil-pump, because that would mean that the flats on the sprocket and shaft would have to be no longer engaged. I guess that this lack of engagement could be for only part of the time (at first), so lack of oil flow could be intermittent.


I imagine that there would not be enough space between the head of the oil-pump bolt and the inside of the front of the sump for the bolt to come out completely. Is that right? Also, do you know which way the oil-pump turns? If it is clockwise when you look at it from the front, then wouldn't rotation of the drive sprocket tend to tighten the bolt holding it on? I appreciate your response - I am trying to understand just how this could have happened.



Cheers
Cheers, Andrew

Pretty much sums it up. The sprocket, like many other components(driveshafts, harmonic balancer as an example) rely on the clamping force applied by the bolt rather than the bolt itself (or in this case the flat)for drive.
The flat on the oil pump sprocket is essentially a secondary mechanism to ensure drive is maintained in addition to the bolt clamping force.
The small pump drive shaft and overall design/build of the pump and critical nature of the oil delivery sytem etc. make the drive flat and bolt clamping force combination a sensible design. Its just LR forgot to ensure the bolt was going to stay tight on a few hundred odd motors.


The oil pump bolt naturally wants to loosen on a clockwise rotating assembly.


My pump bolt was hanging on by a few threads and had marked/worn the inside of the sump.
I believe with a little more time (assuming the sprocket managed to stay engaged) the bolt could have come right out.
The sprocket, now relying soley on the locating flat had progressively worn the flat enough to allow the drive to disengage intermittently and then all together.
The sprocket flat will show signs of wear but mainly the bolt will show wear/damage where the sprocket has rotated on the bolt threads.


It took under 5 minutes to destroy number 1, 2 and 3 jounals at idle.
Number 3 journal had been damaged to more than 3mm oval/undersize with 2 suffering around 1 to 2 mm and number 1 around .5mm.

Hi Strangy, Thanks for further advice. Can you tell me which way the oil pump DOES actually rotate on the TD5 (say, when looking at it from the front)? If clockwise, then I see your point: a normally-threaded bolt would tend to unwind (I got that wrong before!)


isusurover: My engine number starts with "16P" , Compliance plate shows date "03/04". Odometer 183,000 km.


roverv8: I don't think the oil level had risen noticeably after the event. I could not see any water in the oil, or milkiness in colour. No oil in the coolant.


Thanks to all for input, Andrew

Originally Posted by AndrewMilne

Hi Strangy, Thanks for further advice. Can you tell me which way the oil pump DOES actually rotate on the TD5 (say, when looking at it from the front)? If clockwise, then I see your point: a normally-threaded bolt would tend to unwind (I got that wrong before!)....

Thanks to all for input, Andrew

Yes, the oil pump rotates clockwise.


Thanks for providing your engine number prefix.
Common opinion has the 16P unaffected by the oil pump bolt issue, while yours is still to be determined, its good info regardless.


I don't think the 10w-40 oil would have directly caused premature failure.