The Achilles heel of the m5x is its oil pump nut. It’s somewhat common that any m5x engine when driven on track or beat mercilessly on the street will likely run into this issue. To be very blunt, this issue being that oil pump nut backing off or shaft failure.
There’s a handful of solutions to dealing with this.
- wire tie
- welding
- tensioners
- using new parts
- shaft upgrades
- wire tied pump
parkin pump and audi tensioner
It’s not uncommon to see a combination of these to more seriously combat failure.
Welding to the shaft or even adding too much heat too close to the shaft can end in failure. But done correctly, it’s a very effective solution.
Wire has been linked with some failures, but for the most part, people who use it report back success. Wire tie technique is a factor.
With a tightened stock nut, there’s often a bit of play, does that play help prevent the shaft from failure if the chain jumps? We don’t know. Do tensioners that retract actually help? They’re often used in tandem with other solutions, so it’s hard to say under which conditions it helps and under which it doesn’t. It doesn’t hurt.
GSR originally developed the 4 bolt pump solution and is still the most widely regarded m52tu/m54 solution. The Parkin solution is very similar, but uses less hardware and has seen failure. If the watermark left anything to the imagination, it can be found at bimmerworld.
Achilles and VAC offer a single bolt shaft upgrade that is objectively decent, but probably the most work for the end user to instal, requiring pressing the impeller onto the shaft. Achilles has added wire tie to their solution. When I experimented with the VAC solution a decade ago, they recommended loctite to go with this reverse-thread solution.
As these parts have become up to thirty years old, at time of writing, chains are prone to stretch and pretty much all the hardware that comes in contact is prone to wear. During a deeper rebuild, where the timing cover comes off, it makes sense to replace the chains, the crank hub, tensioners and guides. This effectively prevents a lot of issues regarding pump drive failure.
It’s important to remember that these pumps are not all directly interchangeable. Single vanos pumps use a smaller pulley and a different oil outlet hole location on the block than double vanos nonm pumps.
s54 pumps have been retrofitted to work in both setups, though they are more directly interchangeable with with single vanos pumps. Single vanos pumps are usually the s54 choice when going to a sump setup away from stock.
