Sunday 1 October 2023

Dre-XT-Stück - brakefluid sightglass swap

One could kick this post off with some sleazy remark how sightglasses are the vision ports into the brake-system's soul or some rubbish like that. But as a matter of fact, they are actually quite useful in checking the fluid level inside the reservoir and assuming they are clear enough allow you to avoid having your bike's brakefluid tested at the inspection, because it looks fresh after all.

This is not a clear sightglass or in other words, this is the one that has to be swapped out.

I drained all the brakefluid from the reservoir and stuffed it with a paper towel to avoid dirt and metal shavings to get into the actual brake pump.

In order to get the actual sightglass out, I decided to drill a hole ...

Put an M8 bolt through and used a slidehammer to yank it out.

Worked a treat, except the metal ring around the glass stayed in place.

This was less hassle than I anticipated though. I warmed up the housing with a hot air gun and with the lightest bit of prying it came out. (Thanks to the o-ring it's very easy to get behind it.) Using the O-ring as a guide it was also rather easy to avoid damaging the bore.

I bought the new sightglass "on that site" and it came in a bag of three. Don't woryy, they are standardized, so just check the diameter and order a bag of two or three. As I am pretty sure, if you don't, the one you're trying to push in will break.

Warmed up the housing once more with the hot air gun and with a bit of cardboard (to avoid scratching the plastic lens) on one side and a spacer on the inside it pushes in with reasonable force. I used some parallel pliers, but woodworking clamps or C-clamps will definitely work just as well.

Looks a lot better than before and the engineer at the inspection only glanced at it and didn't even remotely consider checking the actual boiling point. (Which would have been fine as I had to refill the reservoir anyway...)

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