Big end bearing shells

[Hawklord]

Whilst trawling the web for oil pressure information for a 300TDI I quite often came across posts saying that the big end bearing shells should be changed at 300,000 km. My Defender has done well over that mileage and the bearings have never been changed, is this something that is worth doing and may improve may oil pressure. 

[joe1]

If they've never been changed they'll be down to the copper now. Mains too! Are you sure they've never been changed?

[joe1]

Thing is once you tear the engine down you'll find loads that need doing....😱

[fmmv]

Is it possible to change the mains in situ? 

[toenden]

No worries. I have had quite some opened at 300k+ km and they have had Signs of use, but only some in real need of a change. In fact one of them, which I positively know have run witout oil for atleast 20 seconds, run without a working clutch for over a year (dont ask....) so it was turner on/off and atarted in gear everytime it needed to change direction and was running well beyond normal boost and diesel amounts was worn but absolutely fine when I gave it new shells. They (main and bigends) can be done from below and the worst part is getting the old gasket of the oilpan 🙂

/mads

[Bowie69]

I wouldn't be tearing it apart just because the manual says so. 

If you have the sump off then by all means check, but don't assume they are bad, especially with how good modern oils are these days. 

[Stellaghost]

This ^^^^^^^^^

If it's not broke...don't fix it.........

Regards Stephen

[miketomcat]

I had an oil pressure issue caused by a new Ali radiator. Once warm the oil goes through the radiator oil cooler straight after the pump, so if the cooler is restricted as mine was you get low oil pressure when warm. I opened up the restriction and the pressure vastly improved.

Mike

[Hawklord]

Thanks for your replies.

They definitely haven't ever been replaced as I bought it 22 years ago with 50k miles on the clock and it has now done 213k miles (343k km).

I have only ever used mineral oil not modern synthetic changed at every 3-4k miles.

It's not broke but hot idle oil pressure is only just over 1 bar and I have read that worn bearing shells can be a possible cause for this.

As the only way to know if they are down to the copper would be to take the sump off and remove the shells to inspect and in my mind having gone that far I may as well replace them anyway, are there any negatives in doing this.

I didn't think that you could replace the mains just by taking the sump off.

I am hoping to get another 5 or 6 years out of the old girl before I get too old and decrepit to be able to maintain her myself and the engine is the only part of the vehicle that has never had anything done to it.

[Hawklord]

Mike, where was the restriction and how to you open it up.

As stated in another of my posts my engine is the one which the longer it is left standing the longer it takes for the oil pressure light to go out (or gauge to move). If started daily it goes out after about 3 seconds but if left for 2 days it takes around 6 seconds, 3 days 9 seconds etc. It has done this for many many years and I have never found out why. The oil seems to somehow drain back to the sump.

[Bowie69]

When I said modern oils, I  didn't restrict that to sytheics, even mineral have much better formulation and additives. 

Just over 1 bar is well within spec and absolutely nothing to be concerned about. Not one bit. 

What filters are you using and do they have a non return valve in there? 

[Peaklander]

9 hours ago, Hawklord said:

Mike, where was the restriction and how did you open it up?

@miketomcat, I was going to ask the same question.

[miketomcat]

The restriction was in the badly made radiator.

(For some reason the photo is upside down but you get the picture)

I opened the hole in the middle up to around 10mm, not nice to do but if you're careful it can be done.

This only seems to be a problem on fully Ali radiators anything with brass or plastic ends is made differently so no issue.

The oil pressure taking longer to build after standing is not a suprise. As all the oil will run back to the sump. Where as some will be left around the system when only a short break. I suspect it's less noticeable on engines where the oil isn't changed as often and those that don't have a guage.

Mike

Edited 4 hours ago by miketomcat

[Snagger]

15 hours ago, fmmv said:

Is it possible to change the mains in situ? 

The big ends are simple to replace in situ.  The mains can all be done except for the aft, just because you need to separate the bearing cap from the flywheel housing on the 200 and the rear crank seal on the 300.  That doesn’t mean you can’t replace all other eight mains shells.

[Sigi_H]

I'd never ever change them on assumption. If they are worn by mileage, a lot else is worn out.