D3 spun bearings video

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Originally Posted by Discodicky

Yes, but you mention a slight taper which is totally different to the crankshaft bearing/shells simply placed into the block and 'hope' they won't spin. I firmly have always felt that not having the locator tabs is the principal reason of the failures.

As you'd be aware large drill bits are tapered and that taper is the only thing that prevents turning whilst drilling the hole.

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In with Shane, the bearings aren't simply pushed in, they are measured for bearing crush first,
The bearing shells will have Larger outside diameter then the block and cap inside diameter. The difference is the crush. They are crush held in place.
The tabs don't do much they are tiny and weak. They are an alignment tool.
Sure I agree they do something. But a bearing with correct crush and no tab won't spin. A bearing with incorrect crush and a tab, will spin.
That being said. I also agree they should be there, just like coolant should be bright green and bond is a man

+1 Josh.

Plus the 140 NM per main cap bolt, then a 90 deg turn ensures proper crush fit of the main bearing. This then points to incorrect sized main bearing shells, plus the top halves are different to the bottom halves as perhaps one of the main contributors to spun bearings.

The argument made in the video is this has been caused by Fabian having to crank to start for a long time due to a failing HPFP. Previous videos have followed the diagnosis and eventual replacement (twice) of the HPFP. Progressive damage caused by the oil starvation (it is alleged) was done to the bearing surface over time till it finally failed.

It also states that broken cranks follow the bearing failure and eventual seizing. This is depends on the time taken in milliseconds to minutes of the shell rotating to block oil and heat up causing the seize up varies depending on each car and what it’s doing at the time. Most seem to get caught at the death rattle stage.

This concurs with Dazza’s observations of relatively few snapped cranks when things go to poop.

Good news is that the top end is in like new condition so if oversized bearing shells are available there’s a good option

Looking forward to next video.