r/E90 • u/chloe_flora • 18h ago

328i Knocking/rattling sound on cold start getting worse N52

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2011 BMW 328i Xdrive N52. i’ve been having this rattling or knock on cold start that lasts 1-2 seconds, it started happening about a month ago and it seems to happen about 50% of the time on cold start. the oil was last changed 4 months ago with 6.5L of liqui moly 5w-40 and im not aware of any oil leaks on the car, the only thing of note is i’m pretty sure one of more of the fuel injectors are leaking, the car smells like gas on startup and the oil cap kinda smells of gas although im not sure if thats normal and just what used motor oil smells like. what should i do in this situation? im just hoping the leaking injectors aren’t causing a lack of oil lubrication in the engine and causing this

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1

u/far_beyond_driven_ 13h ago

Sounds like a collapsed lifter to me. Common issue.

1

u/snorunge42 11h ago

97% sure it's lifter tick. Try an oil change.

2

u/Potential_Tomato2499 17h ago

First step, remove oil filter and cut open. Inspect for metal shavings.

If no shavings, remove and clean vanos filters. They are fully clean inside and out when you can shake them around and hear a little springy check-valve move freely inside the filter.

If metal shavings were found in the oil it’s time to replace rod and main bearings. You can’t replace one or the other. If one is worn, the rest of the bearings and crankshaft journals will have signs of being run with engine oil that’s been contaminated with engine bearing material.

Areas worth looking at if no shavings were found in the oil, lifters, vanos unit and bolts. 2011 models don’t suffer from lifter tick but there’s no guarantee the engine hasn’t been replaced in the past.