M54 oil leak

[Domsz4]

Are there common places where the m54 leaks oil from down at the bottom end of the engine.

I thought it might be the oil level sensor so dropped the oil, replaced the sensor (came with new seals), replaced the copper gasket on the sump plug and cleaned the bottom in every bit I could reach or jab a rag/brush into. Both the engine guard and the big bit of bracing down there were also cleaned.

Leak is still there as I did this 2 weeks ago and the bottom end is covered again.

I tend to park nose down on a slope so hard to see where it might be tracking from but it’s deffo up the block.

Thinking something further up like an oil scavenge or somewhere on the filter housing is leaking or blocked

[Steeler]

Originally Posted by Domsz4

Are there common places where the m54 leaks oil from down at the bottom end of the engine.

I thought it might be the oil level sensor so dropped the oil, replaced the sensor (came with new seals), replaced the copper gasket on the sump plug and cleaned the bottom in every bit I could reach or jab a rag/brush into. Both the engine guard and the big bit of bracing down there were also cleaned.

Leak is still there as I did this 2 weeks ago and the bottom end is covered again.

I tend to park nose down on a slope so hard to see where it might be tracking from but it’s deffo up the block.

Thinking something further up like an oil scavenge or somewhere on the filter housing is leaking or blocked

It's likely OFH gasket leak. Oil runs down casing and soaks bottom of motor.

Also could be, but less likely an oil pan gasket leak.

The other typical oil leak is the VCG. Symptoms of this is smoke from oil dripping on the exhaust manifolds.

[Clearancediver]

OFH… Oil filter housing…. Definitely a contender. Straight forward repair and well within the typical DIY mechanic’s ability. When it leaks, it leaks and drips down the side of the engine into the subframe pan under the engine.

VGH … Valve cover I’m presuming. On the M54 engine (I’m most familiar with that engine as I have it) the Vanos is bolted onto the front of the engine. It creates a transverse joint that the valve cover gasket seals against. TIS requires that a “dab” of RTV be placed on the transverse joint to provide a 100% seal at this point. You also need (TIS) to put dabs of RTV on the half moon joints of the engine where the gasket seals against the engine block… that 90 degree turn creates a potential leak point.

Once you have done those…. Use a high pressure sprayer to clean the engine bay/engine… along with brake cleaner to spray the places the high pressure sprayer can’t reach.

These two “fixes” are cheap to do and only require basic knowledge and skills. Make sure you get good gaskets (not a cheap knock offs)…

Also a potential leak point is the filter cap o-ring. Mine was always leaking for some reason (eventually figured it out)…. But I got a marine clamp (stainless steel) that was big enough to encircle the filter housing at the point where the oil cap was screwed down on. I very very lightly clamped it in place to ensure that the oil ring didn’t bulge out, creating a path for oil to leak. It may garner a sideways glance from a mechanic, but it works…. Never leaked from that day onwards and I never had to worry if the cap was torqued down correctly…..or the oil ring was a cheap counterfeit/poor material (as was the case with items bought online). As I’m older now I don’t do my own oil changes and use the local BMW dealership.

[T-Bears]

I have a M54 in my Z and I have had to deal with leaks all over the place when I first bought the Car. Your leak could be coming from the oil pan gasket. The oil housing gasket is another common place. It is best to replace all gaskets.

Glad I'm done with leaks as I've replaced every gasket excluding HG. Next project would probably be a top end refresh. I had the RMS done during the transmission rebuild glad I don't have to worry about that.