The question: Is it bad if the piston comes out of the caliper and leaks some fluid? I pushed it back in and it doesn't appear to be leaking at all. If this is bad, hwo bad is it? Are we talking catastrophic fiery explosion or slow leak?

The story:
Many years ago, around 60,000 miles, my passenger side caliper broke and had to be replaced. I went to the parts store and picked one up. When I got it home, it was the wrong side but the store was closed and I needed my truck the next morning.
To bleed it, I take it off and use part of an old rotor with the caliper right side up. Once I have them bled, I use a C-clamp to compress the pistons again and put it back on the rotor. I have changed my brakes many times using this method and have been driving on it for around 130,000 miles.

Tonight I went to change the brakes and I spaced out and forgot to put the old rotor in. Some fluid squirted out from the rubber skirt around the piston. I pushed it back in and bled it with the old rotor in it, then put it back on. The brakes seem to be working great and i see no signs of leakage. Driving around the block and braking heavily over and over, the fluid level in the reservoir did not drop at all.

So am I ok, or do I need to replace the caliper (with the correct one this time)?

 

you are probably OK, as long as you didn't scratch the OD of the piston and you didn't roll or cut the seal.

Chances are if you rolled or cut the seal it would leak immediately.

If you scratched the piston (did it fall out and bounce on the floor???) the leak might show up anytime. For instance if the scratch was on the rear of the piston it might not show up till your brake pads are more worn.

The fact that its working OK now is a good sign. Just keep an eye on it for slow leaks. Theres a good chance everything is OK

 

Yes, your caliper is f'd, any leakage is no good. As my rule of thumb, as many others, replace both at the same time. Expensive yes, but could be worse.

You are ok for the time being, don't delay the inevitable too long though!

 

What are you talking about BLUE20004X4??? He states that there is no leakage at all...

 

Wooaahh cowboy, easy now.

The question: Is it bad if the piston comes out of the caliper and leaks some fluid?

That is basically the question I answered. Seeing after that, my impression was that it had leaked and did not appear to be after pushing the pistons back.

Reading on, he then says this: Some fluid squirted out from the rubber skirt around the piston.

Which led me to believe there was a leak, no? Maybe the OP is missing a detail or 2 but it sounds like there is a leak, not major and wants to know how long he can hold off replacing. He said it squirted out from around the rubber seal, not supposed to happen. Just because he later says it appears not to be leaking once everything was back together doesn't mean it is not still leaking, over a while, then he'll notice. Just saying!!

 

BLUE20004X4, I think he meant he pushed it out to far with no rotor inbetween(sp?) the piston and the inside of the caliper and it went past the seal, If thats the case, reassembled the piston should never come out that far so it wont leak.

But BrianD i agree with mkosu04, i once let my brake pads go so far that when i left for the autoparts store the day i was going to change them, i stepped on the brakes and the pad slid out of the caliper and the piston popped out and got ****ed sideways and a tiny chip at the pad end. after i drove back home 2 miles, I put it back into the caliper with new pads and it was fine for the last 10,000 miles. I realy should replace the caliper but money is tight so if my complete catostrophic failure(from lack of maintenence) was fine im sure you will be

 

Thanks for all the responses. The piston came out while there was no rotor in place and the fluid squirted out. The piston did not come all the way out past the skirt, just enough for some fluid to leak out. It did not fall on the floor or anything like that and never came out past the rubber skirt. I immediately put it back in. It went back in part of the way smoothly. Once it started pushing the other piston out, I used a clamp to push them both at the same time all the way back in.

I have been driving it with no issues. I have checked for any signs of fluid around the caliper and wheel and I see nothing. The reservoir also is at the exact same level as when I filled it last week. The brakes are tight and feel good.