TD5 BIG-END BEARING FAILURE

**AndrewMilne** · 15th August 2014, 12:59 PM

Originally Posted by Tank

Andrew, I still believe that #3 con rod is out of whack, those bearings have been spinning in the big end of the rod, there are no locating tangs left on the bearings.
This is caused by a number of defects, 1 the cap bolts were not torqued correctly or have stretched, 2 big end bore not round or oval shaped, or 3 twisted rod, Regards Frank.

Hi Frank,
I agree with you that the bearing shells look as if they have been spinning. As I understand it, TD5 big-end bearing shells don't actually have locating tangs - they are essentially held in place by the "crush" of the bearing cap.
Interesting that DiscoMuppet mentioned an incorrectly-functioning fuel injector. Because when I was at the workshop the day before yesterday, asking whether they could say what was the actual cause of the failure, the mechanic suggested the same thing. I don't know if he knew that was the cause, or was just hypothesizing. I had added the recommended amount of injector cleaner to the fuel for the previous 4 fill-ups, including the last one before the failure. That was on the recommendation of the workshop about a month earlier. Again - in hindsight, I wonder if they already suspected an issue there.
Am I right in thinking that an injector can easily be replaced by taking the cam-cover off?
Regards, Andrew

**Disco Muppet** · 15th August 2014, 01:03 PM

Hi Andrew.
I was simply musing about the injector based on the fact you mentioned the workshop had said it could possibly be a problem, trying to find a link between Frank's suggestions and what the workshop had said.

Yes, rocker cover off, camshaft off, fairly easy to remove an injector.
Info here...

www.discovery2.co.uk / TD5 Engine - Injector Seal Replacement

**Tank** · 15th August 2014, 09:18 PM

If a Faulty injector was firing prematurely it could flog the upper half of the big end bearing causing excess clearance allowing the bearing shells to spin.
It should have shown up as excessive diesel knock and loss of power.
Injectors can be replaced easily though they are numbered and their position is recorded in the engines' computer, someone more familiar with TD5 electronics should be able to advise you how it is done.
If these bearings don't have locating tangs then big end roundness and alignment is even more critical, so I wouldn't rule a damaged rod out, Regards Frank.

**AndrewMilne** · 15th August 2014, 11:52 PM

Originally Posted by Tank

If a Faulty injector was firing prematurely it could flog the upper half of the big end bearing causing excess clearance allowing the bearing shells to spin.
It should have shown up as excessive diesel knock and loss of power.
Injectors can be replaced easily though they are numbered and their position is recorded in the engines' computer, someone more familiar with TD5 electronics should be able to advise you how it is done.
If these bearings don't have locating tangs then big end roundness and alignment is even more critical, so I wouldn't rule a damaged rod out, Regards Frank.

Hi Frank,
What if an injector was not firing at all? Like if it was blocked.
This is what was suggested to me.
I know that some larger diesel engines actually shut down one or more cylinders in the firing sequence to reduce fuel consumption, under certain conditions.
However, what do you think the effect would be in an engine with only 5 cylinders and a fairly small overall capacity of 2.5 litres?
I'd be interested in your thoughts,
Cheers, Andrew

**Disco Muppet** · 16th August 2014, 01:01 PM

It should have been immediately noticeable if it had dropped a cylinder.
They run on 4 and sometimes 3 when you get an oily loom, or in my case it ran on three for about 5 seconds when starting in extreme cold.
It would sound different, run different, etc. Any workshop should have picked up on that though.

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