E90 325i (3.0 N53) Strong Fuel Smell Inlet Side/Milky Oilcap

[mbwoy84]

Got a bit of an issue with a 2008 E90 325i with the 3.0 N53 engine.

There’s a strong smell of petrol, which I’d say is probably worse when it’s cold. You can smell it inside the car, and following my nose it’s coming from the inlet side of the engine. I would say specifically towards the front.

There are no fuel leaks, I’m pretty certain of that, so assuming the fuel smell is coming from vapours escaping from somewhere.

Additionally, when you take the oil cap off, it is VERY milky on the underside and around the oil filler. I would say worse than I’ve seen before from condensation from standing/short journeys etc. The car has been used daily and covers a reasonable mileage, but only generally one long journey a day week and several 5-10 mile journeys. From reading a few things it seems that milky oil caps in cold weather are not unusual on BMWs of this age.

Head gasket issues seems very rare on these engines and I’ve carried out a sniff test which doesn’t seem to show any issues. Not sure if it was just my eyes, but the liquid may have turned very slightly green, but not the bright green or yellow it usually goes upon head gasket failure.

I’ve read about PCV valve issues etc, but the car runs and drives spot on. No sign or rough idle, misfires or anything like that. Other than I’d say it was maybe a bit rattly/tappy, which again I’ve read might just be the fuel system doing its thing when it’s in stratified charge mode.

Any ideas would be welcomed!

[Court_S]

Can’t help re get fuel smell because my old experience of that has been split vent pipes but my wife’s N52 powered cars (previous 125i and current 330i) have both suffered with milky residue under the filler cap in the winter due to the shortish nature of her commute to work (c. 6 miles). It’s never there in the summer.

Might be worth taking the car for a good Italian tune up after cleaning the residue off and seeing what it’s like then.

[helix402]

As mentioned the fuel filler breather can spilt on these. A modified replacement with sleeve is available. Re mayo it’s common in winter on old petrol BMWs. Sometimes worse if the thermostat is weak.

[mbwoy84]

If you mean at the back end of the car, none of the smells are coming from that. It has a recent new electric thermostat, but yes I’ve seen the milky residue is common, but must be something that causes that. Something breather-ish makes sense.

Is it fair to say that if an Italian tune up does get rid of the residue then that would rule out any head gasket issues completely? As it wouldn’t go/would make it worse if there were any issues.

[mbwoy84]

Fingers crossed I think I've found the source of the fuel smell to a fuel pipe from the high pressure pump to the fuel rail. It is a liquid leak, but could barely see it is it was just dribbling a little where the join is covered by a union nut. I've taken it off and it's hard to say, but I think there may be a barely visible hairline crack in the end. It was definitely leaking anyway, so will try a new pipe and see what happens.