I recently noticed this today on the driver's side rear wheel. It goes all around the arch, but seems to be collecting more on the rear.

It's gooey/greasy/oily. My sinuses prevent me from smelling it. I think it's gas leaking from the fill tube because it doesn't show up anywhere else. What else could it be?

thanks.

 

Fuel is not oily and it also evaporates. Gear oil or brake fluid can make a mess like that. Have you experienced any problem with your brakes or checked thd fluid? Gear oil will be much heavier and have the oily appearance.

 

Good call, doc.

I looked at it from underneath, and there was a lot of it all over the back plate. I'm ruling out brake fluid because they've been working fine, and I haven't lost any fluid. I'll check the axle fluid level in the morning. Maybe a bad oil seal on that side.

 

i'd still pull the wheel and drum(if so equipped) and check the cylinders anyway. it still could be leaking but hasn't leaked enough to need to add fluid. this will also allow u to check the rear seal.

 

update:

The brake cylinders and the lines going to them are good. I took out the axle fill plug and was able to get the tip of my finger covered in oil, that's good, but the level has gone down a bit. The mess has gone all over the back of the wheel too, and from there I think it's been shooting around inside

 

The rear wheel seal is bad.

 

^I agree with the doc.