Oil pump replacement/ rebuild consensus

[sapote]

At least you should remove and check the condition of the oil pump pressure regulator piston/cylinder/spring - worn or dirty can lead to low pressure or too high pressure if piston jammed.

[BL92]

Are the rumors true, that the Pierburg is the OE BMW pump with the BMW logo ground off

[WestBankM4]

Is there any detriment of having the DLC coating on the piston without the rest of the components being coated?

I'm putting together my parts for my rod bearing change, didn't even know this existed. I was planning on just taking it apart and cleaning it but I like this item which is surely overkill.

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[JakeM346]

Is there any detriment of having the DLC coating on the piston without the rest of the components being coated?

I'm putting together my parts for my rod bearing change, didn't even know this existed. I was planning on just taking it apart and cleaning it but I like this item which is surely overkill.

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You don't need it. DLC normally works good in combination with aluminium but what people tend to forget is that these aftermarket dlc coating are often not the best quality and therefore you're gonna run into problems with the ZDDP with your oil.
The Pierburg pumps actually come with a coated piston and are in general the best way to go. + you don't have to clean the old part

[BL92]

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SIB110203

[JakeM346]

Are the rumors true, that the Pierburg is the OE BMW pump with the BMW logo ground off

^yes

[ac427]

There is also a coated replacement piston from bmw available for something like 60€. Posted the measurements somewhere some time ago here. But often when the piston is heavily worn/scored the pump is beyond repairable. Price of a pierburg unit is around 400€. At this price, it's not worth playing with the risk of a new crank in my opinion.

Do you have a part number for this replacement piston?