Thread: Why do 2.7 cranks break?

Originally Posted by 101RRS

After now 100 posts to this thread and lots of other similar threads - lots of theories but still nothing definitive.

It’s up there with Who Killed JFK but at least this thread is a one stop conspiracy theory shop

Originally Posted by 101RRS

After now 100 posts to this thread and lots of other similar threads - lots of theories but still nothing definitive.

The reality is you will never get a definitive answer as there are multi-cause failure modes at play with multiple contributing actions and conditions which all prey on the inherent weakness of a 60 degree V6.

What you will get though is theories on how you can mitigate this risk. No single action will prevent failure (short of never driving the car), but there are many things you can do to minimise the risk.

If there was a single definitive answer it would have been addressed by Ford many many years ago.

Originally Posted by DiscoDB

If there was a single definitive answer it would have been addressed by Ford many many years ago.

They would know what the issue is.They design and build engines at many different plants around the globe.

No doubt it’s an engineering or design issue,which cannot be rectified without redesigning the engine,or doing major changes,so they just left it as it was.

And copped a small percentage of failures.
Not ideal,but that is what is happening,with LR caught up in the issue as well.

Originally Posted by DiscoDB

If there was a single definitive answer it would have been addressed by Ford many many years ago.

It was when the Powerstroke 3.0 TDV6 was developed.

I think in the crank subject it’s clear that in some cars bearing shells wear out as Act 1, Scene 1. From there a number of failure modes emerge including a broken crank in some scenarios.

Tangs or no tangs on bearing shells make no difference but for sure lubrication, oil pressure and cranking times have roles to play.

A completely different failure is the belt tensioner on pre 08 cars.

Originally Posted by PerthDisco

I think in the crank subject it’s clear that in some cars bearing shells wear out as Act 1, Scene 1. From there a number of failure modes emerge including a broken crank in some scenarios.

Tangs or no tangs on bearing shells make no difference but for sure lubrication, oil pressure and cranking times have roles to play.

A completely different failure is the belt tensioner on pre 08 cars.

The Powerstroke engine has the same basic system and does not suffer these failures so unlikely.

Originally Posted by 101RRS

The Powerstroke engine has the same basic system and does not suffer these failures so unlikely.

From what is known they did redesign the crank and bearings, and changed the oil spec. But they may have potentially also made other changes to the lubrication system and even the crankshaft damper/balancing to mitigate the weaknesses of the 2.7/3.0.

So most, if not all, of the contributing factors sound like they should have been addressed. Would be good to see the full details on the design changes made. I bet it is a long list.

Good news is the 3.0 Powerstroke has been confirmed for the new Ranger so we may yet find out more on what Ford did to improve the reliability of the engine. Ford will still need to explain more to address any reliability concerns given the same engine was discontinued for the F-150 after only 3 years.

Originally Posted by DiscoDB

From what is known they did redesign the crank and bearings, and changed the oil spec. But they may have potentially also made other changes to the lubrication system and even the crankshaft damper/balancing to mitigate the weaknesses of the 2.7/3.0.

So most, if not all, of the contributing factors sound like they should have been addressed. Would be good to see the full details on the design changes made. I bet it is a long list.

Good news is the 3.0 Powerstroke has been confirmed for the new Ranger so we may yet find out more on what Ford did to improve the reliability of the engine. Ford will still need to explain more to address any reliability concerns given the same engine was discontinued for the F-150 after only 3 years.

Correct a simple non return valve in the oil feed above the pump could be added as per the German’s theory.

That clackety clack sound on startup is your hydraulic cam chain tensioner waiting to get oil pressure.