Easy Brake Caliper Piston Removal - Contraptioneering #1

We have all been there ... or will be soon. A stuck piston in a disk brake caliper. I have seen this described on this site as "the worst job I ever had to do on my XJ". Popular methods include compressed air, and when that won't work, a grease gun (very messy).

They don't come more stuck than the calipers on my 900 that hasn't been ridden for 15 years. During a recent brake overhaul on the 750 I raided the 900 for some pistons. Be darned if they would come out, even with the grease gun !! So I came up with the following bits and bobs to make getting compressed air in there a whole lot easier, and at full compressor pressure of 125psi.

The blanking plate is very simple and made from a single block of 20mm thick UHMW PE with three holes drilled in it. One of these is tapped 1/4 inch NPT for a quick connector and the other two are through drilled at 10.5mm on 96mm centres. The block can be any size as long as it is big enough to cover the mounting and port holes.

The spacers are made from 25 x 10 flat bar with a hole in the centre for the caliper bolt and another hole in just one to match the port. For those interested the offset is 2.5mm on the centre line and 17.5mm perpendicular. You may have to vary the dimensions to match your calipers if thy are different.

On the caliper halves that do not have o-ring seals in them, you will need to assemble the spacers and blanking plate using a little silicone gasket sealant or it will leak.

If you make the plate so it is symmetrical you can turn the spacers around to blank the ports if needed. This makes the device applicalbe to both caliper halves. (you never know which side is going to get stuck first).

The other part of the system is a simple adapter hose and valve made from an old brake line and a quck connector. Between these two gadgets you can put the air into either the main brake line port or the transfer ports on the matching faces.

Finally ... the most important thing !!

If the compressed air won't dislodge the piston, simply pour boiling water over the back of the caliper body with the air pressure applied. The heat quickly transfers through the aluminum body and softens the rubber seals. They just pop out (watch your fingers !!)

 

Nice elegant solution! well done

 

Now that is some straight up 'not going to let this thing beat me' engineering! I love it. Did you sleep on it any whilst you built your caliper rescue or was that an all-nighter?

 

Well it nearly did actually, the first time I tried it nothing happened, the piston was so stuck that full 125 psi air wouldn't move it. The boiling water is what really made the difference, as soon as the caliper heats up the piston just comes straight out.

One point I forgot to add was the spacers move the block out to allow the piston to come all the way out. Once free of the caliper they fire out with tremendous force. I put a rag in there to absorb the impact. You would not want to have a finger in there.

I won't need it again for two years, but it's nice to know it will be a no brainer getting them out next time. Anyone in Oz is welcome to borrow it for the cost of round trip postage, just PM me.

 

that is an awesome solution, very nicely done. I'm going to bookmark this, just in case i ever need to refer back to it.

I'm tempted to just build one for the toolbox... hmm..

 

Every time I've had pistons that 125PSI of air wouldn't pop out, (often) I've used the "grease gun trick" successfully.

I wonder if your grease gun is just "tired."

 

Pour boiling water over the back of the caliper while keeping the air applied and the piston will pop right out.

No grease = no mess.

 

Ohfercryinoutloud. It's my garage. In my garage, grease is not a "messy" thing; it's a part of life. That's what shop towels are for.

Boiling water, on the other hand, is something not readily available in garage-land, so I've never tried it. Not saying it won't work; just never tried it. I like how grease safely accomplishes the task in "slow-mo."

 

The Grease Gun Method won't scald you and cleans up real fast if you are prepared.

Preparation:
Next time you are at the Doctors Office, ... help yourself to some Exam Gloves!

Grease Gun Adapters:
Get yourself the Kit of Grease Gun Adapters that will allow you to place a Zirk Fitting where the Banjo Bolt attaches.

http://www.snydersantiqueauto.com/2522

 

iandmac, when you get one that your hot water and measly 125 psi won't get out, i'll tell you how the adventurous do it

 

Hint the answer is in Polock's ceiling.

 

I think he patched the hole.

You don't need a zirk adapter for the banjo bolt hole; you PLUG the banjo bolt hole.

The stock bleeder screw "end" will engage with a grease gun just like a zirk fitting. Nothing special except a solid bolt required. Plug the banjo bolt hole, open the bleed screw, attach grease gun and pump. Easy.

I do way too much work in the garage to support it by "borrowing" exam gloves. You can buy a box of 100 latex-free, solvent proof blue rubber GARAGE gloves for about $9 at the auto parts.

 

how about some used exam gloves, washed of course..........yuck, i grossed myself out

 

theres plenty of free gloves in the dumpster in back of the red cross....

 

We have electric kettles in Australia, and running water too ...

 

"Measly 125psi" LOL The pistons are 1.685 inches in diameter. That's 2.23 square inches. At 125psi that is 278 lbs force or about the weight of a six cylinder cast iron engine block. When you see how even the most stubborn ones submit to the hot water under that sort of load you'll see what I mean, they have no choice but to come out, and with gusto.

You have me intrigued though ... just how do "the adventurous" do this ... a stick of gellignite or a few grams of C4 perhaps? Or do you fill it with gunpowder and chuck a match in there ?

 

Before I tell you I'll give you some hints, it involves high pressure and hot water but my water was hotter than yours and there was less of it

 

Awww too easy ... you filled it with water, plugged the hole and hit it with a propane torch, right? James Watt would have been proud to see steam pressure still at work 150 years later Good trick, I like it.

Applying heat to soften the seals is the key.

All that's holding that piston in is two tiny rubber seals that have gone hard with age and have crud built up behind them. The piston cannot chemically bond with the caliper body so it isn't siezed.

Hydraulic or steam pressures are not necessary, 20 psi will pop that piston once the seals are warm and squishy.

 

Not really fill it just about a half a shot glass. Warm and squishy is good but I liked the explosion part best

 

So, adopting the Zen "Beginner's Mind" for a minute ... what have we learned and how would we approach this again?

Here's my suggested method:

1. Don't split the caliper, just put a screwdriver down the middle to ensure both pistons come out an equal amount.

2. Get some pressure in there by whatever means (the adapter hose and valve using the end of an old brake line is just one solution, pumping it full of grease with a grease gun is another).

3. Warm it up by whatever means (boiling water or a gentle flame are possible alternatives).

4. Dismantle the caliper and pull the pistons out the last couple of millimeters, re-warming as necessary. A vice with aluminium soft jaws would be ideal for this last step.

 

Is how I intend to approach it the next time... maybe add some gentle heat too.

 

So the jury remains "out" on the best way to apply pressure. So far we have steam, air, hydraulics and Polock's explosives. I'm sure they will all do the same job. Regardless of how the pressure is applied, a first timer will want to do it with the easiest set up possible. Some won't own a grease gun, others won't own an air compressor, others will be nervous about explosives

The awkward bit with this job is not how to get the pressure in, but how to get the second piston out. Once the first one is all the way out there is no way to seal the first bore to get pressure behind the second.

If you get to this situation, and it is easy to do the first time you try this, there's really no alternative but to split the caliper and seal the ports off with some kind of blanking device because it's impossible to get the piston back in without removing the seals, a catch 22 because once the seals are out you can't get any decent pressure into the caliper to pop the second piston.

If you are starting from scratch and take the precaution of putting a bar or similar down the centre it's possible to bring them both almost to the middle, split the caliper then manually pull the pistons the rest of the way out.

 

Polock was only using water; just using it explosively.

Just a little basic physics; elegant in its simplicity.

 

how about put the whole thing in a pot and boil it, let the seals get squishy and soft then put some air to them, when you see one move, block that one and let the pressure build till the other moves

 

add some onions and chives, a couple of parsnips ... brake caliper soup

 

Now we're back in the kitchen again. I still like your "steam cannon" idea.

Honestly, it never occurred to me to pass a propane torch over them before applying air; they likely would just pop out at about 20PSI.

But what fun is that?

 

I didn't mean to give the impression that I object to the boiling of motorcycle parts:



(XJ Valve Cover, poached in Lime Juice with a delicate hint of CLR)

 

So you do have a way to produce boiling water?

 

Oh, ha ha. Not big on water. Fish F*** in it.

 

Ok, this is now well and truly off-topic so lets leave it shall we?

In summary:

Gentle pressure plus heat will dislodge the pistons. Newcomers can sift through the above waffle and decide how best to achieve this.

 

So what's the lime juice to CLR ratio and how long was the missus away ??

And really, citric acid is the working ingredient in either lemon or lime juice, but once you apply heat, lots of heat, why not just burn the rubber at, say 600*F controlled, then clean the carbon ?? (just asking, don't know).

 

Just completed this exercise in removing a seized brake piston using a grease gun. Didn't have a standard bolt to plug the inlet port so fished around the kitchen drawer and found a bamboo skewer. That skewer was not quite big enough to fit into the end of the banjo bolt (at least I think that's what is called) so found some good old duct tape. Once I found the right number of times to wrap in duct tape, I carefully twisted a 1 inch length of the ducted-up bamboo into the end of the banjo bolt. Re-installed the bolt and commenced pumping the brake caliper full of grease. She came out at a measured pace that matched the number of grease gun pumps. Grease clean up was very straightforward, if you've ever used grease before, then you know how to clean it up. I am going to try and attach photos (need to re-size them for the site) for those XJers, like me, who learn by watching, then reading, then doing.

Just another way around the barn.

 

Here are some photos.....not sure they will upload in order but you get the idea.

 

Single sided caliper.

Any means of pressure will get the piston out. Apply heat if really stuck. Was there a large build up of solid gunk behind the seals? I'm talking a millimetre deep here.

But can you show me how to get the second piston out of a double sided caliper with a grease gun (or anything else) after the first one is already out? That's what my device is for.

My 750 and 900 both have 3 double sided calipers, hence my interest in blanking the ports, which is what this post was really about. And I was dismantling two sets, that's six double sided calipers, or twelve pistons. Kind of worth the hour it took to make the parts.

It's a pity this post got hijacked into a sideline discussion about how to apply the pressure as the real message about applying heat to soften the seals and blanking ports on one side was completely drowned out. (I acknowledged grease as a poplular method in the opening two sentences).

Thank you for your feedback, good pics.

 

While on the subject of calipers ... want a great tool for cleaning out those pesky grooves? And dirt cheap too ...

 

plumbers use things called internal pipe wrenches they might get the piston broke loose or a tail pipe expander might grip it tight enough to turn it

 

What a great idea !

I'd say the pistons are cast steel, hard chromed and ground by the look of the flaking near the pit marks. A file won't touch the surface so they have to be at least 60 Rockwell. The problem might be getting a decent bite on the inside because it has been hard chromed as well, just not ground and polished and the jaws on pipe wrenches need to bite a softer material to be effective.

You know if you could just get them to turn a little after applying some heat it might be enough to just pull them out mechanically. It would save a lot of drama. Any sort of expanding plug in the hole should do the trick once those seals are mushy.

Here's another option your steam cannon method inspired ....

Instead of using water, why not use a 25% solution of houshold ammonia that boils at 37 deg C. Just put a good charge into the caliper as you do with water, plug the hole and put the whole caliper in a hot pot and bring it to the boil, slowly.

The ammonia will turn to gas and increase the pressure at 37 deg C and when the seals are hot enough to get squishy the piston will pop out. This might happen at 60 or 70 deg C depending on how set up they are.

Any takers for a trial?

 

I am definitely interested in giving this a shot, but after researching this for 30 minutes, I found no sources describing the temperatures you are refering to - can you find any substantive sources that will reassure me about the temperature needed for ammonia to turn into gas?

Alternatively, I'm thinking of filling the caliper with water, and putting it in the freezer.

 

Awesome job...

Now that I have collected my 5th XJ I have a few sets of calipers I need to pull apart so I might take you up on that offer of borrowing your special tool.
Cheers Andrew B

 

On particularly stubborn Stuck Caliper Pistons; we knew the Rubber Seals were going to be replaced, ... so we'd "Soften" them.

Actually, ... this process turns the seal into Goo, ...
Releasing the tight grip on the Piston.

Wipe the Side of the Caliper Piston with a Q-Tip saturated in Gasoline.
Let some Gas seep down between the Piston and Caliper Bore; where it reaches the Caliper Seal and dissolves it and transform it into the consistency of over-chewed bubble-gum.

 

Rick, I tired carb cleaner on one of mine overnight and it didn't really do much, probably needed to hit it from the inside as well. I think it will work fine whatever you do to soften the seals. The real problem with the double sided caliper is what to do when one piston is all the way out and the other is still stuck in there.

ol_750 pm me your address and I'll post the tool to you ... let's see ... six pack per week sound like a fair rental? LOLs

splazoid ... if you go here:

http://en.wikipedia.org/wiki/Ammonium_hydroxide

there's a table on the right hand side showing two boiling points for the different concentrations of 25 and 32 percent solution. It should say it on the bottle what the concentration is. The cheaper the brand the more water it will have in it and the higher will be the boiling point so I guess Home Brand is the go, probably 10% or something. Let us know how you get on with it.

I would caution against freezing the caliper ... aluminium expands (and contracts) at roughly three times the rate of steel, if you freeze it the caliper may seize on the piston and nullify the pressure effect. Also the idea of heating it up is to make the seal turn into goo because it is the seal that's holding it in there and if you chill it it will just get harder.

 

Hi Iandmac,
Is the offer for your special tool for brake piston removal still on the table.
I have a few calipers to get pistons out of.
I'm up to 2 x 750RL's & 4 x 900's (33F)

Cheers ol_750
Andrew B

 

I personally used the boiler method on my single piston calipers: Tighten the bleeder screw, fill with water, plug the brake line inlet, point away from you, heat with a blow torch until it comes out unexpectedly making you jump three feet sideways. Also, not sure if this is the case for all XJs, but I found that the bolts used to mount my calipers were the same size as the banjo bolts, so I used one of those with a few wraps of teflon tape to plug the inlet before heating. I also tefloned the bleeder screw just for good measure.

 

grease gun worked like a charm for me.

 

Thank you all for this information! It's great that these old threads can be referred back to. Last night I was able to plug the brake line hole and install a zerk into the bleeder hole. I boiled the caliper for about 15 minutes then began the process of pumping grease into the caliper. Shazam! The piston began to slowly move out. Then I ran out of grease! Ran to the store bought more and it was still warm enough to push the piston all the way out.

Great idea!!!

Thanks again,

Todd