Yellow fluid leaking

[z4notop]

Hello I am a new BMW owner and new to this Forum. I have 2003 Z4 2.5. I bought this vehicle recently and have found yellow fluid leaking under the engine. It has a slight oily feel. I have checked the antifreeze fluid (not yellow). Would appreciate any assistance. I tried a search on this forum but could not find an answer. Thanks in advance.

[silverfishZ4M]

Nm you have a non M

[Jstic]

Most likely brake fluid. The DOT4 fluid I use has a yellow/golden color.

[GuidoK]

If it aint coolant, it can be motor oil (only yellow when extremely fresh), transmission fluid (yellow-brown for manual fluid, red/brown for ATF), diff fluid (yellow-brown), windscreen wiper fluid (any color but not oily) or brake fluid (mostly yellow and 'rough' oily feeling).
Those are the liquids in your z4.

In case of leaking brake fluid it's obviously not recommended that you drive a singe yard in your car as your brake system is not reliable anymore

[swifttiga]

Had the same thing on 08 Z4 coupe They did not find any thing. It was in line with the hinge for the front door went away and everything still works so I continue driving. Does the motor mounts have fluid fill?

[StickMon]

Originally Posted by swifttiga

... Does the motor mounts have fluid fill?

Let's poke one and find out.
Yep, but it doesn't look to be yellow.

[z4notop]

Thanks everyone I have put paper under the vehicle and guess what.......... not another single drop. I have driven the car another 100 miles and nothing. Will continue to watch. Thanks again for your assistance.

[Finnegan]

Very crazy idea here. Rodent urine? Doubt it would be oily, but still. If small patched.

Like I said crazy idea.

[msh441]

BMW has used... I'm not sure if it's an adhesive, or some kind of assembly lube... During the production of its cars. I saw quite a bit of it on my old MINI and see it here and there under the hood of my BMW.

It's yellowish-brown in color. Most of what I've seen is dry/solid, but I remember some of it being a little tacky when the MINI was brand new.

If it's collected around body panel seams could be your culprit. I never had enough to leak to the ground outside the car, though.

[Finnegan]

^ Interesting. Hmm.

[Westersund]

Originally Posted by msh441

BMW has used... I'm not sure if it's an adhesive, or some kind of assembly lube... During the production of its cars. I saw quite a bit of it on my old MINI and see it here and there under the hood of my BMW.

It's yellowish-brown in color. Most of what I've seen is dry/solid, but I remember some of it being a little tacky when the MINI was brand new.

If it's collected around body panel seams could be your culprit. I never had enough to leak to the ground outside the car, though.

That yellow/brown stuff can be some sort of wax that may or may not be used for vehicle assembly. My dad's M535i -87 still has it under the hood, maybe even under the car (haven't checked).

[silverfishZ4M]

my old VW has that yellow wax, but it only appears during very warm weather. They use it to fill the inside of the doors for rust protection. During the summer, it leaks out and looks like bees wax all over the bottom of the door. Not liquid though.