I have never been able to see anything worthwhile in either of the two brake reservoir sight glasses. If I try looking in the sight glass and pump the brake a bit, maybe I can see a bubble or two. Then again, that might be my imagination. Also, perhaps my vision is not great. Nevertheless, those little "windows" seem about worthless to me. However, it sure would be nice not to have to crack the tops of the reservoirs just to check the fluid level.

Please let me know what any of you with pilot's vision see, if anything, when you look. And if so, do you use any technique that makes the fluid level readily apparent. Thanks.

 

A flashlight and a wiggle of the bike in the garage is usually all I need. No need for the flashlight in daylight/outdoor inspections.

 

If you are low on brake fluid you might see drops on the floor (indicating a leak) beneath the bike or you will notice it when you push on the rear brake lever. A low level of fluid or maybe worn out pads would translate into a longer travel than normal on your brake lever. I never look at the level in the sight glass. I guess if you had to initially charge your brakes it might be handy, but not necessary.

 

That's normal, I can't see mine either however, it was designed like that. If the fluid was low, you would see a lighter color in the sight glass which would indicate low fluid. When the sight glass is dark, then your reservoir is full. Harley put the sight glass in the reservoir so you don't have to take the lid off to see if it's full. Brake fluid will eat the paint away if you spill it on the paint. Good Luck.........don't spill

 

Mine works just fine. Small air bubble with the bard hard over to the right while on the side stand.

 

I had the same thought too. This past wknd i finally cracked them open to check. Sure enough was low, once i brought the level up, the sight glass went solid black. Before filling them the glass looked clear, similar to the bubble in the pic posted in a reply before mine.

 

Here's a note from my '07 service manual (sight glass on the top cover)

"The sight glass allows a visual check of the brake fluid level without having to remove the master cylinder reservoir cover. The sight glass is dark when the reservoir is full, and lightens as the fluid level drops."

So if it looks black or very dark, the level is good. It's dark even with new fluid as long as it's full.

 

If you didn't have a leak that caused you to add brake fluid:

Be careful when you change brake pads. If you push the pistons back in without opening the bleeder screw you'll overflow the the master cylinder and the gasket under the lid won't hold it. If it didn't leak out, it's down in the caliper(s) because the pads are thinner.

As a rule, I always crack the bleeder screw when pushing brake pistons back in. It makes it easier and it gets dirty fluid from behind the pistons out that might not otherwise be flushed out with new fluid. The fluid behind the pistons has had the hottest duty cycle. Then I add new fluid to the master cylinder.

This process should be done when bleeding a DOT 5 system as well. DOT 5 is silicon based and is not hygroscopic (meaning it doesn't attract and hold water) like DOT 3, 4 and 5.1. When moisture/water enters a DOT 5 system (braking systems are not truly closed to moisture) it will be at the lowest point (the calipers) and should be removed by the aforementioned bleeding procedure.

DOT 5 will not harm paint as it's silicon based, while glycol based 3, 4 and 5.1 will. DOT 5 is not recommended for ABS systems due to the potential for aeration (bubbles). While DOT 5 is more expensive; because it isn't hygroscopic it doesn't need to be changed as often. And when you do change it, a spill isn't a big deal. I use it in our non ABS Harleys and DOT4 in the one that does have ABS.

One last note: When gylcol based brake fluid has attracted moisture it becomes dark. The darker the fluid the more moisture content there is. Moisture in a braking system will compress when fluid temperatures reach the point where water boils (212F). At that point the water/moisture turns into a gas and will cause the lever or pedal to go soft or even bottom out without providing leverage to the pads. This is known as brake fade and can happen with a few repeated applications of the brakes at high speed or on curvy roads. It's all dependent on how much moisture is in the system (lowering the effective heat resistance) and how hard and often the brakes are applied.

Way more than you asked, sorry about that.

 

Good information, thanks. Some people go many years without changing brake fluid. I've decided to just change it every third year. Some would say that's not enough but I haven't had a problem yet.

 

I bet the brake fluid change gets skipped a lot. On my last bike I changed the fluid at maybe the 5 year mark, old fluid looked fine. I'll probably change the fluid on the Limited as scheduled. I ended up getting one of those vacuum gun things, makes the job a bit easier.