[Fitz335]

Fixing a oil pan leak and pulled off the oil pan today. Laying in the bottom of it was a broken bolt. Quickly discovered it was the bottom oil pump bolt. Looks like it snapped off near max depth.

Anyone with experience with this? What's the cause? There a solution so it doesn't happen again? Going to try and back the rest of the bolt out with a left handed drill, praying I don't have to take off the oil pump.

[feuer]

It does happen. Not the first case. It has been documented. Is not the debris but lack of oil pressure cause by loosed oil pump that is damaging the engine. Some bolts, the longest I think, require 180 degrees after you torque it and that is too much I think. You can feel the bolt twisting when you do it. Try without removing the pump but you might have too. All of those bolts are single use so you need to buy new.

[rbryantaz]

BUMP: This is an old thread but an important one!

While doing an oil pan gasket on my N54 (and the rod bearings while I was there) one of the 33mm oil pump bolts snapped in my N54 engine just like others have observed which was also mentioned in the DIY rod bearing video I was referencing...

First of all: +1 on not using an impact when removing these.

Mine was already broken and just loose in the pump where it hadn't vibrated out yet. Fortunately once the pump was removed I could just screwout the broken portion with a pick tool so it wasn't a big deal to get it out.

My concern is that when these break they could cause the oil pump to come loose which would cause the engine to lose oil pressure which needless to say would be very bad...

I upgraded my N54 to use steel alloy bolts for the oil pump bolt kit.

Alloy bolts CANNOT be used on the N52 engine (due to its magnesium engine shell)

Alloy bolts are an upgrade for the N54/N55 and are used on most BMW other BMW engines including the M54, M57, N62, N63, S63, S65, etc. BMW just made a common bolt kit for the N52/N54/N55 to avoid the possibility of someone putting alloy bolts in the N52 and causing a major corrosion issue between steel and magnesium alloys.

Here is a picture of the hardware I used. Thread lengths and bolt lengths were checked carefully with a set of calipers.


Bolt length and unthreaded lengths along with thread engagement were checked carefully

• The long m8 oil pump bolt specifically there was about 9mm of extra threads and I got 18mm+ of thread engagement. The original bolt clearly did not use most its threads.
  
• The short oil pump bolt is slightly longer but there are plenty of threads for it.
• The longer oil pickup bolt unthreaded portion is easily shorter than the distance from the pickup tube to where the thread start (6mm below the block)

For my RWD N54 (xdrive will have more bolts) from the top counter clockwise: Long M8 oil pump bolt, Short M8 oil pump bolt (2 needed), M6 windage tray bolt (6 needed), M6 oil pump chain guide bolt(2 needed), M6 Oil pickup bolt (3 needed).
Note: I did use the same M6 bolt for the chain guide and the windage tray.

I ordered black washers but they didn't arrive in time so I used some zinc ones that I had on hand. There is no rust concern inside of the engine so the black oxide bolts work great (rod bolts are generally black oxide).

These torque specs were taken from other BMW aluminum block engines that used 8.8 or 10.9 bolts for various internal engine bolts....

M6 10.9 into aluminum is 12-14Nm
M8 10.9 into aluminum is 22-24Nm. (The M8 bolts I used are actually 12.9 but I still used the 10.9 torque spec due to the aluminum threads really being the limiter not the bolt and this is already tighter than the factory aluminum bolt)

I also used a dab of blue loctite on them to make sure they don't loosen. Loctite is more risky on aluminum bolts that could snap when removed but not a concern for alloy bolts.


I have extra bolts if anyone else is interested in a kit.

I am looking at also changing out the oil pan bolts to zinc alloy bolts that are both reusable and won't break.

Steel bolts are a much better match for aluminum than stainless (stainless can cause galvanic corrosion in some cases). Zinc coating is only needed for bolts that are on the outside of the engine.

-Rich

[NZE90]

Originally Posted by rbryantaz

Alloy bolts CANNOT be used on the N52 engine (due to its magnesium engine shell)

Alloy bolts are an upgrade for the N54/N55 and are used on most BMW other BMW engines including the M54, M57, N62, N63, S63, S65, etc. BMW just made a common bolt kit for the N52/N54/N55 to avoid the possibility of someone putting alloy bolts in the N52 and causing a major corrosion issue between steel and magnesium alloys.

-Rich

FYI alloy bolts are used on the N52. Oil sump bolts, water pump bolts, early valve cover bolts etc are all alloy.

It's steel bolts that cannot be used on the N52 because of the magnesium.

[rbryantaz]

Originally Posted by NZE90

FYI alloy bolts are used on the N52. Oil sump bolts, water pump bolts, early valve cover bolts etc are all alloy.

It's steel bolts that cannot be used on the N52 because of the magnesium.

Thanks! Yes I agree, I should have said alloy steel not just alloy (almost all metals are alloys). I will fix it.

Note I was in a hurry last night and didn't want to wait for an order of bolts to arrive so I did install the oil pan with factory aluminum alloy bolts.

My torque wrench records the max torque during the angle turns. I was reaching only 17-18Nm on most of the bolts which is lower than what I would do for an alloy steel bolt.

The pan seems less critical than the oil pump bolts. If I have it off again I will use steel bolts with washers next time.

-Rich