PDJ said:sharif said:Why did the bearings need doing so early?
From what I have found out about this issue is,
BMW when designing the S54 engine started with a 3.0ltr and bored it out to 3.2ltr so the pistons became larger in diameter, to make the rotating mass less they reduced the width of the connecting rod bearings narrower.
So the pressure on the rod bearing has now increased bigger area pressing on a smaller area.
They also used a bearing material that was not up to the job in the early S54’s fitted the the M3’s this was sorted with a recall later S54 engines in the Z4’s had the new rod bearing material
They also upped the weight of the oil to help with the issue now 10/60 this brings it’s own issues as it is too thick at start up and you have very high oil pressure for a few mins so hence the careful warm up phase of driving these cars.
Also sometimes the first owner does not have the mechanical sympathy as it is under warranty and only plans to keep for a couple of years so under their ownership everything is ok.
Time or distance between oil service is too long as the general public like new cars that don't need to a keep popping back to the garage so long service intervals became the norm
Also once the car is over the threshold to be an approved used BMW it is no longer sold by a BMW dealership and the subsequent owners are sort of on there own, so it is unlikely BMW will spend any time or money on out of “approved BMW” BMW only want to sell cars that maintain the brand
So as this issue becomes more understood the best way to avoid an engine rebuild is to replace the rod bearings and check the oil pump and relief valve before a failure
Just my thoughts/findings
Thanks PDJ.
Before purchasing my MC, I did a lot of research regarding common problems and the rod bearings seem to be discussed frequently.
The car was a 3 owner car, however, I did not know how it had been driven before purchasing it and thought it would be best to get it done as a preventative maintenance measure. The cost of having the bearings replaced as opposed to the cost for an engine rebuild is low. I went with genuine BMW bearings and bolts.
Unfortunately, I've had some bad luck with cars in the past (i.e. engines failing a month after purchase), so for me it was peace of mind to just get them done!
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![IMG_2013[1].JPG IMG_2013[1].JPG](https://z4-forum.com/data/attachments/64/64395-948fd30f3d0fc25b75785be3c30c2f2a.jpg?hash=rdF294xpPn)
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so new water pump and thermostat fitted by Joni and the team at glasgowbmwminispecialists.co.uk



