Thread: Why do 2.7 cranks break?

Originally Posted by 350RRC

I have no doubt that's true!

Was just a play on Dazza's comment about a D4 being 'one of the best 4x4s on the road'.

cheers, DL

Some of the junior lurkers may not have understood the intent of your words of wisdom, so thought it might be worth commenting on/clarifying. We all know they are unbeatable off road, plus of course LR is responsible for much of the old and recent technology, which is then taken up and utilised by other marques.

Originally Posted by V8Ian

It certainly appears to be a minimalist design, possibly taken too far.

Happy to be corrected on any or all of what I'm about to write.

When my 3.0Ltr Twin Turbo failed i couldn't understand why, so I researched the bejesus out of it and spoke to many engine rebuilders and to an engineer. What I (and I alone) have concluded is that the crankshaft momentarily twists. Not bends! When something is twisted it takes on a helix shape and in doing so, then it will try to bend and effectively shorten. Being wedged in by hefty main bearings the crankshaft (in this case) can't really move that much but it will move enough to bind against the (in most cases the No.2) main bearing and rotate it slightly, it may only rotate the main bearing a little or a lot, either restricting the the oil journal or completely block it. As with mine, the bearing was only rotated slightly restricting oil flow as I got another 5,000 Km after a slight bearing noise was evident. So slight, that I was the only one who noticed a difference in engine sound at around 1800-2200 RPM. My reasoning for the 2.7 having less failures is simply the less power they have, but occasionally there is a "perfect storm" where the 2.7 will also fail. Knowing when mine first made the new engine noise, I was decelerating and suddenly needed to accelerate, it came on boost early (I'm guessing) and put extreme pressure on one or two cylinders.
This is the reason I went for a billet crank over standard

As i said, this is my interpretation only and I'm happy to stand corrected, but to me sounds very logical.

Please don't rip into me if I'm completely wrong.

Originally Posted by Eetab

Happy to be corrected on any or all of what I'm about to write.

When my 3.0Ltr Twin Turbo failed i couldn't understand why, so I researched the bejesus out of it and spoke to many engine rebuilders and to an engineer. What I (and I alone) have concluded is that the crankshaft momentarily twists. Not bends! When something is twisted it takes on a helix shape and in doing so, then it will try to bend and effectively shorten. Being wedged in by hefty main bearings the crankshaft (in this case) can't really move that much but it will move enough to bind against the (in most cases the No.2) main bearing and rotate it slightly, it may only rotate the main bearing a little or a lot, either restricting the the oil journal or completely block it. As with mine, the bearing was only rotated slightly restricting oil flow as I got another 5,000 Km after a slight bearing noise was evident. So slight, that I was the only one who noticed a difference in engine sound at around 1800-2200 RPM. My reasoning for the 2.7 having less failures is simply the less power they have, but occasionally there is a "perfect storm" where the 2.7 will also fail. Knowing when mine first made the new engine noise, I was decelerating and suddenly needed to accelerate, it came on boost early (I'm guessing) and put extreme pressure on one or two cylinders.
This is the reason I went for a billet crank over standard

As i said, this is my interpretation only and I'm happy to stand corrected, but to me sounds very logical.

Please don't rip into me if I'm completely wrong.

You can never be completely wrong, if no one knows what is completely right!

I've been gonna post this for a few years, but didn't due to the unprovable nature of the info..but anyway, here we go..

Old school diesel tech says this:

Very few companies have built ultra reliable V configuration diesels in the past, particularly if they are relatively high output for size.

The crankshaft has just over half the length for a given number of cylinders compared to straight, so less meat and strength.

There were reports years ago of some V8 diesel crank cases twisting when under extreme load, which would damage the crank, but would keep running for a little while before realised, leading people to believe the failure happened randomly.

A local LR indie has seen more failed engines on these than most have, and I was informed the first part of the failure is a spun bearing, but of course if you don't hear that, crank next.

That's mainly on the 2.7.

Lack of oil changes will cause worn bearings, if an engine has failed due to crank or bearing, the OTHER bearings that are intact could be assessed for wear which would tell the story a bit.

A possibility could be a momentary failure or prolonged partial failure of the relief valve in the oil pump.

More likely would be crank end float out of spec, faulty conrods/bolts etc.

And as it's related..

The oil pump tensioner housing only ever seems to fail AFTER a belt change, this is unlikely to be caused by an over tensioned
Belt, unless it was maxed out.

Some I've changed have had the bolt extremely tight, and loctited in, the pressure used to undo it was considerable, in fact I think I damaged the thread doing it, but that's ok as I was replacing the pump anyway , this could be a partial cause...but of course fatigue will play a major part.


In fact, I'm suffering from that right now.

Cheers
James

People say that no one knows why the 2.7 and later the 3.0 engine break their cranks - well that is not correct. The maker of these engines (Ford) know exactly what the cause is - for sure some engines may fail due to rotated bearings, worn bearings, poor maintenance etc but in the main I think it just happens because the crank is just not strong enough to handle the forces when as mentioned loads on the crank all come at once. (may break at a later time after being stressed) - afterall some have failed with only 40,000km on them and others have failed with 400,00km.

My thoughts as follows are not based on anything mechanical but based on Ford's marketing.

In the US we all know that they have Lemon Laws that can be very costly to manufacturers if they have a stuff up and produce a lemon. Now Ford wanted to introduce the 3.0 TDV6 into the Ford F150 but of course using a short engine which is basically the same as LR with all its faults would be a recipe for disaster.

As we know Ford's (PSA) 3.0L diesel engines have serious problems with bursting crankshafts and quick wear on crankshaft bearings. There are several possible causes - a design mistake, insufficient oil pump performance, improper oil, untimely and incomplete oil change. The reason is most likely a complex of the above factors. For the 3.0 Powerstroke Ford did a lot of work on the old engine and developed a revised crankshaft and bearings.

I did see a comparison chart of the crankshaft journal sizes of the PSA Lion 3.0 and the Powerstroke 3.0 but cannot find it now. However, the crankshaft journals are approx 4mm larger in the F150 over the old crankshaft (approx 69.9mm vs 65.9mm).

While there may have been failures of the Powerstroke, there does not seem to be any record of systemic crank failures. So to me the base cause is simply the old crank was not big enough and this fault has been corrected in the Powestroke.

Garry

why does the terry motor not break cracks like the landy motor ?

Originally Posted by incisor

why does the terry motor not break cracks like the landy motor ?

The Ford badge screwed to the rocker cover provides superior reinforcement than the Land Rover badge…

Originally Posted by incisor

why does the terry motor not break cracks like the landy motor ?

The cynic says Ford determined which engines went to which customer.

The truth is probably more like the Territory is lighter, has an easier life (soccer mum duties), and does less kms than the Discovery.

The Territory also got the later version of the 2.7 like the D4 - and by all accounts the D4 with the 2.7 also has less failures - supporting that improvements were made over time.

Originally Posted by DiscoDB

The Territory also got the later version of the 2.7 like the D4 - and by all accounts the D4 with the 2.7 also has less failures - supporting that improvements were made over time.

The improvements,if any, seem to be a mystery?