Q. Brake fluid leak after changing front pads?

[jaydee]

Hey all,
Just a home mechanic and I have done heaps of pad changes on various cars over the years.
Something new today, CX5.
First I did the right front pad change.
After compressing the piston the new pads went straight in no probs.
Did the left side and pushed the piston back in, put in the pads no worries.
Started the car, got the pedal to come back after a few pumps.
Then I noticed a fluid leak on the garage floor, checked I hadn't split a hose, no, checked under the bonnet.
Could see fluid had run down the booster, and I thought maybe the master cylinder was gone, but on closer inspection it looked like it might have come back through the cap, run down the master cylinder to the booster and dripped down.
I've never had this happen and I didn't have to compress the pistons much.

So could fluid have been forced back into the MC forcing it to come out of the cap?

[simon varley]

yes. that's why you don't top up the reservoir if it drops

[Fatbob103]

It was obviously at full level with the old pads and pushed back when you compressed the pistons.

[aussiblue]

yes. that's why you don't top up the reservoir if it drops

Or leave the cap on while pushing the pistons in; something has to give under that hydraulic pressure.

[jaydee]

OK, thanks everyone for the responses, that is what I assumed had happened.
But as I said, never happened before.
I'll know for next time.

[Citroënbender]

It’s a good time to suck the reservoir dry with syringe or pump, wipe with a clean cloth (if accessible inside) and then top up with fresh fluid once pads are all in.