To cut a long story short, whilst cleaning up the pistons on a LX disc brake I pumped it out a bit far an lost the oil. The piston remained in the caliper but leaked oil from beneath the piston. The nice folks on Singletrack gave lots of encouragement and I pushed the piston back in, bled the brake and everything seemed fine.

I mentioned it to a mechanic at a LBS today and he seemed pretty adamant that the caliper needed rebuilding with new seals as it would continue to leak, folk on here seem to think it would be fine. So, am I safe to go or not?

I tend to get a bit anal about having things 'safe' and just right; too much so. I don't want to spend cash replacing perfectly good kit but the front brake is pretty critical in safety terms. The bottom line is that despite pumping the brake hard I can see no evidence of leakage. I've ridden the bike today and it functions as before, stopping the bike nicely. I removed the pads and the backs are dry and I can see no leakage; lever travel hasn't increased or gone spongey.

Any thoughts (hope a second thread is ok r!)

Should be fine, happened to me with some formulas, when I was trying to fix a sticky piston. Re-bleed and is fine, I didn't change the seals.

LBS in talking sh1te shocker 🙂

the LBS are just trying to take you money

as i said yesterday just ride it but be a bit cautious with it until your confident with it again

LBS is wrong, I feel.

Absolutely no need to rebuild the caliper, or replace seals.

When cleaning, replacing or upgrading (older Hope metal to new phenolic for example) pistons, you can simply pump them out and slide them in again – as long seals are lubed with brake fluid and they go in straight, and there is no debris/mud/crud.

Hope that reassures : )

when a piston comes out of the caliper and is replaced it is very easy to damage the seals. However seals ae either damagedand leaking or not. clean the caliper up and check for brake fluid. if not any leaks now then its fineto use

Yeah, sounds as if the shop is looking to get some work from you! Hold the lever back and pump it at the end of its travel and look for any evidence of leaking and see if the lever gradually works its way back to the bars. If it all feels solid then it's fine!

It seems fairly solid at the moment. I guess I was worried that there was a weakness that might suddenly give out. The piston didn't actually come out of the caliper, but it did lose all it's oil pretty rapidly. I think it worked out at a bit of an angle, so maybe just came out of the seal at the bottom. It did take a fair push to get it back in though.

On the plus side, it seems to have got me over my 'fear' of messing with hydraulics and when I initially opened the resevoir before the leak there didn't seem to be a lot oil in there, so maybe they needed topping up anyway (it was a pre-bled set).

I'll keep an eye out for any leakage, I assume that if fluid was leaking out, air would be getting in that the lever would feel spongey and travel farther.

And it will make the most amazing noise as leaking fluid wreaks your pads. 😉

It wont die straight away though – even if its totally wrecked you will get enough notice and should even be able to finish the rides. If your mates can take the noise!

can you get shimano spare seals? I thought you couldn't.

unless you did a very bad job of putting the piston back , bearing in mind the rear of a shimano piston is beveled and designed to help locate into the seal i doubt it will have torn it , lack of sharp edges n all

unless the mechanic showed me the seal weaping id be inclined to leave it , sounds to me like he is pulling a fast one. (and thats from a fellow mechanic …)

paulsoxo you cant get "shimano" spares but extract them and buy some out of an RS catalogue type place , our local bearing place does seals . The shimanos are a standard componant that you can replace with a like for like item out of a catalogue in there …. we just take in the seals we need and they supply the correct item back.

well it sounds like I'm okay. Thanks to everyone for the reassurance. I will keep an eye on things for a while though and if the worst comes to the worst I've seen some replacement calipers for around £20. I think that a caliper rebuild might be a bit beyond me.