26 replies to this topic

[Covert]

In my eyes using grease is the easy safe option , ive seen many a piston fired across the workshop when some has used compressed air , thus damaging the piston in the process , might be a little messy on clean up but by far the easiest way

[dklawson]

 

This is a new one on me, in all the years of working on cars I've never heard of/seen someone using a grease gun to do this. It seems like such a bad idea, getting the grease out of the callipers must be a nightmare to the point I'd want to just chuck them in for refurb units!

 

 

It's actually a pretty old DIY method used when other tools are not available.  If you have the calipers off the car and the pistons are stuck, using grease to pump the pistons out is safer than compressed air and not a particularly bad idea.  The intention here is to get the pistons out with the least amount of damage with the understanding you will be rebuilding the calipers anyway.  You waste a lot of grease but after that it's only a question of effort cleaning up everything.  The bulk is removed by scooping and wiping it out of the caliper bores, the remainder is blown through with compressed air followed by normal washing, finishing up with spray brake cleaner.  

I cannot afford to throw away items like brake calipers. 

[Ben_O]

The other option is to weld a piece of thick rod across the inside faces of the piston and then clamp a pair of mole grips onto the rod and then you can twist/pull to get it out

[AlexMozza]

I usualy put an air line up the fluid in, and gently pulse air though it, pops the pistons out :)

[Lincsminbin]

Being a biker on the side, I've spent an alarming amount of my life stripping calipers, they seem to pick up all the rubbish off the road and seize every 5 minutes.

I've seen the grease method used, but never done it myself, it looks like a nice controlled way of removing a stuck piston without damage. I've also seen air lines used, which (everytime I've seen it) is 100% effective and mind numbingly dangerous

I tend to pump them out as far as I can whilst on the car and then work them out with some piston pliers. I also use silicone grease for reassembly, it's safe on seals like rubber grease, but not as sticky.

If you do split the calipers be careful not to over tighten when reassembling, I don't know if it's a problem on minis, but the calipers are generally far softer than the bolt and the thread can be stripped reasonably easily.

[Spider]

I know most workshop manuals say to use compressed air, but as they other guys have said, I think this would be potentially quite dangerous and possibly mess. I don't know for sure, as I've always felt it too dangerous to even give it a try.

 

I've not done the grease gun method either though heard of it done several times now (seems a waste of grease but if that's all one has,,,,)

 

On nealy all, I've managed to pull the pistons by either gripping them on the ID (many have a groove for this) or using Vice Grips (of course, replacing the piston after).

 

There was one though that wouldn't budge, I ended up welding a nut in to it and using a slide hammer.

 

What ever method, I really think Compressed Air should be avoided at all costs.

[FlyingScot]

I just use a track pump (for road racing bike) with a modified brake hose. Much safer than compressed air and it always shifted them enough to grab the piston lip with mole grips and once done removed the hose and pushed piston through the hole for one side.

FS

[Fast Ivan]

I've used compressed air, nice and gentle on the throttle, no problem. I can see them flying across the workshop though if you go to mad, or if they're a bit seized and then give suddenly being an issue

[joet999]

When using compressed air I put the calliper inside a pillow case or tee shirt that way if it comes out at 100psi it doesn't fly off like a loose cannon.

[Daniel_moody25]

Hi guys, starting to rebuild now and having trouble getting the wiper retainers in, any tips to get them is cause they looks pretty fragile and I tried with the ones that came out first and I just kept bending them ones

[Spider]

I think I may have hinted at that in an earlier post. I've found it best to get them started 'flat' ie, not get one side in and work around, as they just expand out and you'll never get that last bit in. They can be a ripe pain and yes, I have damaged a couple. (note to self, must make a internally tapered tool)

[Stu1961]

Recently split a surplus to requirements pair of 8.4" calliper's, thought I would refurb them just in case I ever fit 12" wheels Pushed one piston out with a pin punch inserted through the brake pipe connection. The other one I got out by placing a nut and bolt inside the pistons recess and turning the nut until it tightened then pulled out with a pair of pliers. Worked well.