Wilwood master cylinder sight glass

For a while I have been trying different ideas to keep tabs on the brake fluid level in my Wilwood master cylinder. Every time you want to check the level you have to remove the top which is fixed with four small Allen wrench screws. One of my ideas was to add a float level that I connected to my brake light switch. For this I got a new Wilwood cap and gasket. Drilled a hole, connected a float level, completed wiring, etc. It worked well except that it allowed fluid to sip between the gasket and cap, which them leaked through the screws and vent hole. The source of the issue is that I couldn't seal the hole between the gasket and float rod. After many tries and different fixes I gave up and went back to no float. Now I wonder if one could drill the wall of the master and installed an NPT threaded sight glasses. There are a few options out there. However, this will require drilling of the actual master so it doesn't work it is not as cheap as a new master cap. In any case, I wanted to post here and see if anyone has come up with a good idea.

To some it may sound like a waste of time. I know I know I can leave without it and just rely on unbolting the cap but a part of me thinks there should be a better way. I still would like to have a warning light so if the sight glass idea worked I wonder if there is some kind of electronic switch that can be activated through the sight glass.

PS: first post, long time reader. I have a heavily modified 1971 Mustang that I drive on the street, take to 8-10 autocross and 3-5 track day events throughout the year.

You're talking about installing something along the lines of this? (Maybe a different size, thats whatever)

There's minimal pressure in the actual reservoir, I think it could work.

https://a.co/d/jfYWIV5

Personally, since the top is less expensive to replace, I'd look at drilling it and installing a solid piece of clear acrylic (or some other material that isnt damaged by the brake fluid) deep enough to reach to the "minimum" line.

Shine a light on the acrylic, if it is in contact with fluid it will have a different color than if the fluid is lower than it.

The problem is that under the top you have the gasket and once you drill the gasket the fluid starts leaking that's the issue I had when I tried the float. Thanks.

This is one of the Wilwood masters with the cast aluminum integral reservoir? Lots of options for sight glasses there, ones that are designed to seal. Same with level switches. It'll be easier to seal against a rigid aluminum body than try to maintain the integrity of the gasket on top with a float - all you'll need will be an O-ring. I'd rather do a sensor than a sight glass, as then you'll have constant information instead of relying on occasional manual checks. 

You could also swap in one of the remote master cylinders, which use clear reservoirs.

Is there enough room to replace the Allen key screws with thumb screws?  If you don't have to bust out a tool, but could just remove it with your hand, that might solve the problem without more invasive modifications.

All the thumb screws you could ever want:

https://www.mcmaster.com/products/thumb-screws/thumb-screws~/

In reply to BA5 :

I tried that idea as well but opted for keeping a small Allen wrench attache to a magnet by my shock tower bar.