UK-POLOS.NET - THE VW Polo Forum

hello

when doing a brake fluid change on a polo 9n with fs 3 calipers , i noticed that when putting the cap back on the bleed nipple, brake fluid seeped out. i know that i did everything right because after driving for 10 minutes brake fluid did not seep out anymore. what had caused the fluid to seep out when i put the cap on? does fluid remain around the threads?

to confirm i did everything right , i sent 10 psi down the MC, i saw nothing seeping out around the threads. what causes the small amounts of fluid to seep out? does fluid COLLECT around the threads?

Fluid can collect around the threads

If its not dripping now its nothing to worry about

I have been changing brake fluid on cars I've owned for years and until recently, had never ever seen this happening. When it first happened to me I was also a bit confused, so just to play safe I replaced the bleed valves as they are softer than the calliper and if they get overtightened they can end up with a stepped area to seal on instead of a point on the taper. That seemed to stop the weeping of fluid, though like in your case, I was convinced that fluid was not being lost from the system, it was only fluid that had ended up being forced up around the threaded area during bleeding. I seem to remember even spraying the area with brake cleaner to make sure that no more or very little was still being forced out or trapped fluid being expanded due to heat in the callipers.

I'm sure that I've seen some sort of grease etc used on the bleed valve threads of newer cars, there is a bit of logic there as any compatible grease used on these threads would stop moisture and dirt getting into the threaded area and so avoid any corrosion forming that would make removing the bleed valves difficult - and would also stop the fluid running up the thread.