Brake Fluid from MC when compressing Pistons

Master Cylinder has overflowed and leaking fluid. I did the passenger side brake pads which no issues. The drivers side is a different story. I have changed brakes numerous times. Drivers side when i started compressing the pistons i noticed fluid dripping. Looked under the hood and the MC was topped off and fluid coming out. Has not done that to me before. Did i do something wrong? Any information will be very grateful.
Should i siphon some out the MC because it hasn’t gone down. I pumped the brakes and even went down the road

 

It sounds like you had too much fluid in the mc before you compressed the caliper pistons you lucked out with the first side, caught up with you on the other side the fluid had to go somewhere……….

 

So if the MC was normal when i checked before i started after about an hour ride home would it be too much in the system?

 

“Normal” does that mean full to the top? Depending on how far the pistons were extended, how worn were the pads? When you collapse the pistons the fluid is pushed back into the mc if there’s no room the fluid gets pushed out causing the leak. The fluid most likely came out the top and ran over. It’s happened to me before. Is the mc filled to the brim now? Others might chime in but I say put it all back together and clean it up remove some fluid if it is over flowing and test the pedal, do you have a good pedal, does it stay firm without drifting down? If you have a good pedal you are most likely good to go. Obviously test the brakes well before driving away.
Good luck

 

I was going to do a flush anyway so lil get it out tomorrow morning.
Had about an 1/8” of pads left and pedal feels normal and it’s still full to the top. I got nervous because that’s has never happened to me.

 

Topping off the fluid over the life of the pads to an 1/8” then collapsing the pistons with all that fluid behind them will do it. I think you’re gonna be ok but check the brakes before driving off.
Good luck

 

I will Thanks

 

Many vehicle brake reservoirs are actually designed in such a way that when the front and rear brakes are worn out the brake fluid level will be low enough to trigger the warning light although in most cases this doesn't occur because front and rear pads wear at different rates and they tend to get "topped off" during normal service.
With that said most likely your fluid was topped off when the pads were partially worn and when you compressed the calipers it overfilled the reservoir, once your new pads are installed correct the level to the full mark and leave it.

 

To the OP just to be clear it is not leaking form the actual master cylinder, it's leaking from the reservoir cap?

It's normal for fluid to come out when compressing the calipers for new breaks. I usually take the cap off, put a rag around the fluid reservoir and do the drivers side first. Normally you can get away with one side without removing some fluid. Also, the cap on the 3rd gen actually let's fluid out the top from that nipple, it has like a fluid release in case it builds to much pressure.