Water in Left Boot and Behind Seat – Feels Oily, Not Just Water

[detch]

I’ve run into a weird issue on my E85 Z4 and could use some insight.

After washing the car with a pressure washer (I sprayed the roof seams, third brake light, trunk edges—basically all over), I noticed quite a bit of water pooling on the left-hand side of the boot, as well as in the left behind the seat storage compartment. The second place was especially worrying because when I took it out - i poured like a cup of liquid on the ground.

Now here’s the strange part:
The water isn’t just plain water—it feels a bit slimy or oily, has no smell, and maybe a slight yellowish tint. It’s definitely not washer fluid or coolant (no blue or green), and it’s not hydraulic fluid either—my roof works fine, the pump is dry and full.
And when I touched it - I felt my paper cuts sting a bit.

I think the water may be seeping in from the top of the left wheel arch, possibly working its way into both the boot and the storage compartment. I’m not 100 percent sure where it starts.

I’ve already:
– Replaced the cracked third brake light
– Cleaned the roof drain pipes - the left one was REALLY clogged.
– I sealed the left tail light metal bracket with silicone.

And now I'm waiting for the rain or next trip to the pressure washer.
I am however mostly puzzled, why is the liquid "oily". Is it maybe the "juice" out of the old BMW sound deadening?
Maybe it's related to the loosely thrown bags of moisture absorbers. They were all hard as rock... maybe after a while they "let go" of the water or something?

Has anyone seen something like this?

 

[bigwinn]

Are you sure that the fluid isn’t roof motor oil…

If your drain points are full (like you noted) and they fill up and overflow you’ll see the water accumulate there- and if the pockets are blocked causing the hydraulic pipes to rust you can get pinhole leaks of the fluid under pressure.

Worth a check

Assume the motor is in the boot area now?

 

[detch]

Ah yes, I moved my pump to the boot. I also inspected it and the reservoir looks near full. Everything around the pump is absolutely dry.
I didn't check the whole loop though.

I fought with my previous convertible MK1 Audi TT pump and I know the symptoms of a leaking system. How the roof becomes slower and slower, the squirting sounds in the back etc.
And that's why I also know the feeling of a spilled hydraulic fluid because I have absolute vietnam flashbacks.

However when I poured out the liquid from the rear cubby on a white paper towel - it definitely wasn't blue/greenish like the liquid in the pump.

 

[bigwinn]

I can’t think of anywhere else oily residue water would come from

The common water ingress points are blocked drain where the motor sits, door membranes and the seals around the cabin filter.