s54 rod vs main bearings

[Rombbb]

Hello,

The rod bearings apparently are a concern but how do you know if main bearings require replacement too ?

That's a much bigger job than only replacing the rod bearings it seems.

Internet is full of rod bearings. Nothing much on mains.

Were they somehow designed better and generally left ok or is it better while doing the job to replace everything in one go ?

 

[Smartbear]

They’re not going to suffer as much as the big ends in a relatively long stroke high rpm engine.
Rob

 

[griffnut]

Those main bearings in the photo ( not "M" bearings but a purely a representation of how worn bearings.) look quite worn, you would have to measure thickness of the bearing surface with a micrometer to determine the amount of wear over standard new bearings.

 

[srhutch]

You’ll get so many opinions on this. My bmw Indy suggests changing at 70k as piece of mind.

That will take me another 10 years or so at 2k per year. Also me and my oil is changed every 4K and never driven over 3k till fully worn so engine is treated sympathetically which should help.

 

[GuidoK]

Those main bearings in the photo look quite worn,

Are you sure these are s54 main bearings? (or even s54 bearings in general? :roll: )

 

[Mr Tidy]

When I was speaking to Ross (Bowser134) about them he said he'd seen more cases of head gasket failure than rod bearing failure on S54s.

So when mine had it's Inspection 2 done at 76K miles I asked him to get an oil sample analysed - time will tell!

But I hadn't heard anything about main bearing issues before. :?

 

[AndyBeech]

When I was speaking to Ross (Bowser134) about them he said he'd seen more cases of head gasket failure than rod bearing failure on S54s.

So when mine had it's Inspection 2 done at 76K miles I asked him to get an oil sample analysed - time will tell!

But I hadn't heard anything about main bearing issues before. :?

Can do a leak / compression test for the head gasket. Pretty straightforward to do. Just had mine tested and was fine at 90k miles.

Main bearings, not something I’ve come across tbh or been advised to do.

 

[GuidoK]

Main bearings are much less under load, and certainly due to high revs, especially because the I6 is also very much in balance.
High torque would be more of an issue I imagine, and that's not an s54 trait.
Also the I6 crankshaft has 7 mainbearings, which makes it a much stronger construction (every conrod is enclosed by 2 mainbearings) than say a v8 or v6 crank which has bearings enclosing 2 conrods.
(also a reason why I6 engines are usually way more popular in industrial applications where endurance is more of an issue than space or cost)

 

[bakes100]

Those main bearings in the photo look quite worn, you would have to measure thickness of the bearing surface with a micrometer to determine the amount of wear over standard new bearings.

The photo is not of S54 main bearings..

 

[Argenta]

Haha what a scam photo

 

[R60BBA]

Wouldn’t bother doing main bearings unless the engine is super high mileage, at which point you might as well take it to Redish and get a full rebuild for £4,000 all in.

https://www.redish-motorsport.com/BMWE46M3S54EngineRebuildRefresh.html

 

[Status]

If it ain’t broke

 

[XMetal]

If it ain’t broke

But if it did, it will go KABOOM

 

[Status]

But if it ain’t broke then it ain’t broke is it so leave it until it needs sorting

 

[mmm-five]

But if it ain’t broke then it ain’t broke is it so leave it until it needs sorting

Mine wasn’t broke, until it broke, on the way from the Ring (luckily not on the track) ...which meant a potential £5000 rebuild (went for a low mileage replacement engine instead) rather than £1000-ish preventative maintenance...plus a fight with the recovery company about repatriation.

Mine was at 160,000-ish miles.

 

[XMetal]

But if it ain’t broke then it ain’t broke is it so leave it until it needs sorting

How do you know when it needs sorting? By the time it makes noises, it's too late. If it doesn't make a hole in your block, then it's a potential £5000 rebuild as mmm-five saids or a new motor if it does make a hole in the block when it fails.

 

[Mr Tidy]

When my car had an Inspection 2 last month my Indy kept an oil sample so we could get it analysed to see if there was any trace of metal from the shells in it.

Hopefully there won't be, but if there is it'll be time for new shells.

 

[where.is.lee]

But if it ain’t broke then it ain’t broke is it so leave it until it needs sorting

Mine wasn’t broke, until it broke, on the way from the Ring (luckily not on the track) ...which meant a potential £5000 rebuild (went for a low mileage replacement engine instead) rather than £1000-ish preventative maintenance...plus a fight with the recovery company about repatriation.

Mine was at 160,000-ish miles.

guess it comes down to luck of the draw, how many track days prior to it going bang?

 

[PDJ]

My rod bearings replaced at 87000 as preventative maintenance

 

[Superzetti]

My rod bearings (on the S54 motor / Z4M) replaced at 89.500 km also as preventive maintenance.