Thread: Why do 2.7 cranks break?

Don’t make up stats

Originally Posted by 101RRS

I cannot see this line of discussion having anything to do with 2.7 cranks braking

It's as credible a line of discussion as any other discussion on TDV6 cranks breaking. Wild speculation is all we have, so don't go trying to be the fun police now.

Anyway, we learned a few things about the oil cooler and flow that we didn't know before, so it's not entirely a waste of electrons.

I believe lubrication issues are at the core of why bearings spin and this leads to breaking the crank. Seems to be more prevalent with the 2.7 than the 3.0 but I don’t have any stats on this.

I also believe that a large % of these failures are related to undiagnosed symptoms that if acted on early could have lead to a different outcome.

So putting aside pure crank failure (without a spun bearing), or original assembly issues (which should have failed by now), at present the leading candidates for why these fail are:

1. Oil specification.
2. Oil life.
3. Oil starvation.
4. Oil contamination.

Land Rover I believe took an easy way out to just blame oil spec without acknowledging there is more to this story, but they may be 100% correct and in which case the solution is as simple as use 5W-30 oil to Ford spec wss-m2c913b and follow the LR schedule and procedure for oil changes and you are 98.7% likely to not have a snapped crank.

I think with some good insight though we can do better than that and bump it up to 99.9% (yes I made up these stats).

Originally Posted by BradC

It's as credible a line of discussion as any other discussion on TDV6 cranks breaking. Wild speculation is all we have, so don't go trying to be the fun police now.

Anyway, we learned a few things about the oil cooler and flow that we didn't know before, so it's not entirely a waste of electrons.

I think it’s a super important Aulro discovery (pardon pun) as literally the whole world is pointing to the oil filter on top as the worst possible design as all oil flows back to sump on shutdown and the pump needs to fill it all up again especially after a long shutdown. We’ve shown that not to be the case as long as the NRV works. Maybe that’s a fail point maybe not.

Originally Posted by PerthDisco

I think it’s a super important Aulro discovery (pardon pun) as literally the whole world is pointing to the oil filter on top as the worst possible design as all oil flows back to sump on shutdown and the pump needs to fill it all up again especially after a long shutdown. We’ve shown that not to be the case as long as the NRV works. Maybe that’s a fail point maybe not.

An interesting test will be timing the oil light after a change, vs after a cold sit.
Mine is pretty consistent in the morning at about 3 seconds from turn of key (not fire up) after sitting all night. Next time I do a change I'll have to remember to time it accurately. When I want to get precise I use a video camera and count frames. Tacho needle moving to oil light out would be a good metric.

There are oil galleries to the cams, crank and lifters. I do wonder how much (if any) oil weeps back to the sump via the mains when the engine is off but hot. Given the mass of oil in the heads, there'd be a bit of pressure under gravity for that to weep back. The lifters are going to drain also. So despite there being good flow after sitting, there's always going to be low pressure until the galleries and lifters are filled.

I honestly think this is jumping at shadows. Unless the bearings are dead dry, rotational movement actually sucks oil from the gallery to fill the space left by the hydrodynamic wedge as the journal rotates. If it was such a problem, the mis-placed filter would cause instant engine death before it was backed out of the driveway. The usual report is "it sounded a bit funny and died a fair way down the road". It'd go a fair way on just the oil in the galleries before it started to scrape up.

Originally Posted by PerthDisco

We’ve shown that not to be the case as long as the NRV works. Maybe that’s a fail point maybe not.

I have followed a lot of threads on this topic from all over the world and no one seems to discuss - what if the oil filter assembly has a fault, let alone talk about why the NRV does not always work.

There is a great thread on LR-Club.com that got close, but then the discussion just stopped after almost 800 posts. I won’t link to it because they swear a lot.

Ford/PSA/JLR don’t even state that there is a NRV, let alone the role of the filter spigot. Instead they just talk about a full flow bypass that should never be needed (but don’t define where it is).

Any day you learn something new is a good day. Plus more fun than discussing COVID.

Just side track a bit on the topic of how long you can run an engine with no oil.

In my youth I may have been involved in several attempts to kill an engine through oil starvation. On one occasion, we gave up (we possibly ran out of beers). This mighty little Toyota engine refused to die despite being revved flat stick for hours and hours. No oil, no water, it just ran and ran. The RSPCA (A for Auto) would have laid charged against us.

So I agree 3-4 seconds even on every start should not be a problem……but you are knocking off little bits of bearing with time and if it grabs it spins.

This is where the thinner / low friction oil theory has a lot of merit to not put too much drag on the bearing shell when the oil is cold.

The counter argument is it is under hot conditions that you spin the bearing when the oil is at its thinnest and hence the thicker / wear protection oil theory comes into play.

Originally Posted by Tombie

Don’t make up stats

Well prove it is not so .