Is it possible to overfill your Brake Fluid reservoir?

[SpencerPJ]

I'll just be honest.

 

Last year I topped off my Brake Fluid, all was fine. Recently I had noticed front brake pads, very thin, so today I changed them out. Prior to compressing the pistons, I tried to remove reservoir cap, and both screws are crap, I tried a hand impact, I'm too afraid I will break reservoir, and screws are crap.

 

I know I need to drill them and fix with some SS screws as Dingy has once posted. I also know I need JIS screwdrivers for future projects.

 

My question is? I loosened a bleeder screw and let little bit of the fluid out that way. I have all back together, brakes work great, but my sight glass does not show ANY air at the top. What would be the downside of an overfilled reservoir. Will 'heat' and expansion be an issue? I know I need to correctly fix, But I'd like to put off for a fall/winter project.

 

Any comments would be appreciated, thx

[Flyinfool]

Yes you can over fill. The result will be dragging brakes of to the point of locking the wheel. It is somewhat common to have the rear lock up after brake work when it is over filled.

 

What happens is the brakes drag slightly, maybe not even noticeable, but that creates heat. As the fluid gets hotter it expands, the only place to go is to push the pistons out of the caliper, this makes not heat more expansion......... You will first notice what seems like a loss of power untill the brakes finally lock the wheel. If you have a bleeder wrench with you, you can simply crack the bleeder to relieve the pressure and be back on your way.

 

Or just bleed a bit of fluid out until you are at the correct level and not worry about it until you get the screws fixed. But DO keep a wrench to fit the bleeder screws stored on the bike just in case.

[Patmac6075]

The downside is it sounds like you've unintentionally introduced too much air into the system. Seems unlikely, if you had a tiny air bubble in the sight glass before you bled some fluid off.....that now you would too much brake fluid in there?! Most likely is you cannot see any brake fluid in the glass now.

Remedy is to get those screws replaced, refill with clean brake fluid, and do a proper bleed.

[Vonwolf]

If he had to compress the caliper to get the new pads in it will fill the reservoir with more fluid, especially if there was fluid added over time to make up for the calipers pushing the thinner pads out. I go thru pads fast in my truck when I change them the reservoir look near empty, after the new pads it's full again

[SpencerPJ]

Ok, that's what I thought. Thanks Jeff, I'll let a bit more out and carry a wrench.

[Yammer Dan]

I wouldn't even let any out. Just check to see if it is getting warm. If it is then let a little out . There is a chance of getting it too low?? Just keep the wrench and some paper towels with you. You don't want any of that stuff on the plastic!!

[MiCarl]

The other thing you need to worry about is some of the fluid escaping from the reservoir lid and dripping on the plastic. It'll ruin ABS plastic almost instantly.

 

You need an impact screwdriver. Both Harbor Freight and Sears sell them for $20. The "Phillips" bits are JIS. A few sharp smacks with a plastic mallet should break them loose. That tool is a must have for your tool box.

[SpencerPJ]

Oh all places, I found the exact SS screws at Menards, and modified a screwdriver with the grinder, and got the screws out. AMEN