XSeries-forum

Hi guys,

I have a 2005 4.8is with 136k miles on the clock with only what I can describe as being a "medium-to-major" oil leak!

I took a 30 mile drive yesterday and when returning I parked it up in the garage with a folded out cardboard box and drop sheet underneath. I have attached a photo showing the amount of oil that dropped to the floor. The engine was directly above the cardboard box and the drop sheet runs to the middle of the car. Having done some Google/ChatGPT research this could most likely be the alternator seal leaking under pressure while driving and then the wind blowing the oil all the way down the bottom of the car towards the gearbox, and then dripping like this when stationary.

What would your thoughts be? Could it be something else, other areas to check?

How hard is it do replace the alternator seal as a DIY mechanic on axle stands?

Worth also having a look at the front crankshaft seal. Have a look from above and see if you can see what’s wet.

Can’t help with how possible repairs are with just axle stands as I’ve never tried it.

X5Sport wrote: Fri Jun 05, 2026 7:56 pm Worth also having a look at the front crankshaft seal. Have a look from above and see if you can see what’s wet.

Can’t help with how possible repairs are with just axle stands as I’ve never tried it.

Excellent, thanks for the additional input.
Going to get it jacked up at the weekend to take a closer look and take some more photos.

Front Crank seal most likely as said , alternators don't have any oil in them to leak out , changing it yourself on the drive will be a right pain and very challenging going by others experience on here

Leslie wrote: Sat Jun 06, 2026 10:56 am Front Crank seal most likely as said , alternators don't have any oil in them to leak out , changing it yourself on the drive will be a right pain and very challenging going by others experience on here

Apologies, I wasn't clear enough. It's not an alternator oil leak but rather an oil leak from a seal within the alternator bracket. There is a high pressure oil line/feed running through the alternator bracket that has a seal that is notorious for failing and leaking a lot of oil.

Here's a photo of what I'm referring to, courtesy of this outpost.com link:
https://xoutpost.com/bmw-sav-forums/x5- ... e_vignette

X5Sport wrote: Fri Jun 05, 2026 7:56 pm Worth also having a look at the front crankshaft seal. Have a look from above and see if you can see what’s wet.

Can’t help with how possible repairs are with just axle stands as I’ve never tried it.

Thanks for that. I've had a look from the top around the valve cover and crankshaft seal area and although it is greasy and moist it is not very wet, like under the alternator bracket where there is a Lot of oil (could just be gravity now while stationary).

I've attached some photos of what I am seeing but will degrease and clean all the areas in question, then drive 20-30 miles and look again as to where the majority oil is accumulating and leaking out. Hope that gives me a better idea.

This shows oil moisture and dirt/grease build up above the alternator. Another shot above the alternator. Could this be a oil pressure sensor seal leak too at the front of the camshaft cover? Photo from underneath showing a lot of oil moisture on the left side (UK passenger side) of the subframe etc. These two photos shows a lot of oil dripping off what looks like the alternator bracket area.

Last time i had oil every ware like that it turned out to be the oil filter leaking well the "O"ring on the cap to be precise.
With fresh oil we couldn't see it well at all and i had driven the car for 3 weeks before it started leaking.
Hope you find your leak soon.

Get it cleaned and see whats left , driving blows the oil all over so best to just let it idle a while and have a look. v8s would be scarse over due to fuel cost.

Alan Gunn wrote: Tue Jun 09, 2026 5:47 am Last time i had oil every ware like that it turned out to be the oil filter leaking well the "O"ring on the cap to be precise.
With fresh oil we couldn't see it well at all and i had driven the car for 3 weeks before it started leaking.
Hope you find your leak soon.

Great suggestion Alan, I'll take a look at the oil filter o-ring while I'm there.
It's starting to look like I've got multiple oil leaks rather than one....