• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Stuck Piston in Brake Calipur

Share this page

L

LanceLyon

Jedi Hopeful
Offline
Seems like everything is frozen on this project! My newest challenge is getting the pistons out of the calipurs. After removing the calipurs and cleaning them up a bit, I applied some line pressure to push the pistons out. On both calipurs it took over 100PSI to get one of the two pistons moving. The second piston in both calipurs is now stuck. I've tried to pry gently, at first, on both sides of the piston at the groove for the rubber bellows. Solid. The pistons that came out show rusted patches and will need to be replaced, so I am assuming that the pistons that are still frozen are even more rusted.

Any ideas on how to get a grip on these things?
 
Mark,

You must be more wealthy than I am! I think new calipurs run about $400 each. Besides, it's all about the journey, isn't it?
 
LL,
The first step is to get the brake line loose and the bleeder out ,it sounds like you have.Next fill the caliper with Aerokroil(serious but also joking from a earlier post)Let it soak overnight.In the mean time make up a fitting to go from a porta power to your caliper(we will skip right by the air and the greese gun)Put a piece of flat stock between the pistons (adjust this so that the pistons come out even)I just reread your post, put the the piston you got out back in, I blocked the moving piston somehow but I cant recall right now how but it was not that hard to figure out, and pump away slowly,practice extreme caution.Be prepared to spend time hand cleaning grooves in the calipers.I had some very!!! rusty calipers that had sat outside for years, they are rebuilt and work fine.When you get them out repost for the next steps.
CDK

[ 01-15-2004: Message edited by: CDK ]</p>
 
CDK,
I'm not familiar with "porta power". I've ordered some of the Aerokroil per your earlier posting, and for now am soaking them in PJ Blaster while I consult you guys!
 
A "Porta Power" is a small hydrolic(sp) jack used to move very heavy things a small distance, body shops have them alot and constrution guys but basically the jack piston is connected to the pump with a hi pressure hose if you take the ☼☼☼☼☼☼☼☼ the hose and plumb it to your caliper you will have a very good pump however refer to previous warning of using caution.After you use it for awhile you will see why I like Kroil.Dont use it on just rusty stuff you will be amazed at how many ways this stuff can work for you.Its a little pricy but the can seems to last forever if its cold it looses it perpelent somewhat just get the can warm and it will work again.
CDK
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by LyonLance:
Mark,

You must be more wealthy than I am! I think new calipurs run about $400 each. Besides, it's all about the journey, isn't it?<hr></blockquote>

You must have cought my post in the 2 min it was up before I deleted it. I was thinking about wheel cylinders at first.

Disk brake calipers are on a whole different financial level than $35 wheel cylinders. If they are badly pitted inside, there isn't much to do about it other than replace them or have them professionally redone...

[ 01-16-2004: Message edited by: Mark Beiser ]</p>
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by CDK:
...take the ☼☼☼☼☼☼☼☼ the hose and plumb it to your caliper you will have a very good pump....
CDK<hr></blockquote>


Or you could fill the caliper with Aerokroil and hook it to the brake system, bleed the disk and use the car's master cylinder to push it out. When we were working on our project-Sprite and it has a stuck caliper, we temporarily swapped it with one on the racer and used the race car's hydraulic system to push the piston out. Brake systems can generate 1000 psi easily.
A friend of mine who does repairs has a master cylinder mounted on a bench setup for just this purpose. He has a single flex line coming out of the master cylinder and a home made lever to operate the cylinder.
 
Echoing CDK here...

I usually use hydraulic power to remove stuck pistons.

In the cases where one piston comes out and the other is hopelessly stuck, I've split the halves (as a last resort only) and bolted a flat plate that was drilled and tapped to accept the hose from the porta-power. The plate is then bolted across the caliper's internal fluid port (using an o-ring, as reqd.) a few strokes on the pump and the caliper piston is in your hand.
 
Aloha LL,

I had the same problem with brake calipers on my TR3A. I had removed the calipers and used an air compressor to push the pistons out, unfortunately only one piston came out. I cleaned the bore of the one that came out and that piston. After liberally using Liquid Wrench on the outside and filling the caliper I let it work overnight. The cleaned piston was put in the caliper and using a C-Clamp held in place. With air pressure I was able to get the stuck piston out. It may not come out on the first attempt, but if you get movement, you can work it in and out to totally free it. Be careful to not **** the piston in the bore. I used a C-Clamp to push it into the bore and keep spray the lubricant/rust cutter. Keep fingers out of the path of the piston, because it will come out with force. Also try and protect the opposite side of the caliper with a thin piece of wood, so the groove for the rubber seal is not damaged. Good luck.

Safety Fast,
Dave
 
This is one I can contribute, Don't want to do this again...All pistons were rusted on our BT-7.Pulled the Calibers and removed all lines. Soaked PB blaster for a couple of days. Then we pried the pistons up with two screw drivers opposing each other at the same time. Bends/tears up the dust cover ring but 75% of the time you'll need to replace the piston anyways.
As the piston slowly works up, take small vice grip pliers and clamp them opposing each other on the rim of the piston. Now you can pry between the base of the caliper and the top of the plier. Not pretty and not quick but works and just takes patience. Our pistons were rusty but the cylinders were shiny. Replaced pistons with Stainless Steel. It' been a year and no leaks!!!! We have another BT-7 and split the caliper on the left front. Hand surfaced the faces with sandpaper laid flat on a solid surface (Table Saw)replaced the little round gasket between the calibers (where the fluid runs) and torqued it all together and no leaks their either. Good luck, Shelly
 
I just spoke with a friend on the phone, who suggested soaking the entire caliper in muriatic acid for 10-15 minutes to disolve the rust. He claims that he has used this technique many times in the past and it works great. It's not compatible with aluminum parts, but I believe that the calipers are all steel.

Has anyone heard of or used this technique?
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by LyonLance:
Has anyone heard of or used this technique?<hr></blockquote>

Yes, but take the phone off the hook!

I one time put a pair of "duckbill pliers" (similar to "needle nosed pliers") in Muriatic Acid to disolve some rust they aquired from being left outside on a production platform in The Gulf of Mexico. I checked them after a few minutes and decided that they needed a little bit longer soak time. Then the phone rang...

When I remembered the poor pliers the next day and fished them out, the cutting jaws were about 1/4" from touching when the handles were closed! I threw them back in the now black solution and looked for them a day later. They were gone.

And here's another long forgotten tip:
You can use Muriatic Acid to sharpen a dull file. The acid will etch those teeth back to a point.

I made alot of money betting people $5.00 I could sharpen their old files!

"File" that one away with the wax trick!

[ 01-16-2004: Message edited by: Randy Forbes ]</p>
 
I used two metal bars and two C-clamps to hold the piston that came out just slightly inserted. After reconnecting to the brake line I used the brake petal and popped out the stuck caliper. I could pull the clamped caliper out easily. Did this successfully twice, first when I rebuilt the brakes re-using the old pistons and later when I got religion and replaced them with stainless steel.
 
I just went through this earlier this week. I ended up pulling the calipers apart and grabbing the stuck piston with my visegrips (I was replacing the pistons anyway). Twisted back and forth for a few minutes and walla it came out.

Just finished media blasting the calipers today getting ready for new paint, seals and pistons. They are going to look bitchin in bright glossy yellow through my wheels.
Rob
 
As an update to the project, I ended up soaking the stuck pistons in "BJ Blaster" for a couple of days to begin with. The free pistons were re-inserted into the calipurs and clamped into place with a "C" clamp, about half-way down. Padding was inserted between the stuck piston and the clamp, and then increasing air pressure was applied to the calipur until movement was detected. Once the pistons started to move, I used some gentle prying along with judicious use of air pressure to remove them. What a project, and thanks for all of the various bits of encouragement and advice!
 
Laugh if you want to but this works every time. Get a grease fitting and take the brake bleeder screw out of the caliper. Tig weld the grease fitting onto the bleeder fitting. Ok so you have to buy new bleeders so what 50 cents each. Replace the bleeder screws with the welded grease fittings on them back into the caliper and get a grease gun and pump them out. It has worked when air, screwdrivers, visegrips and all other methods have failed. Skip
 
I just had mine rebuilt by White Post Restorations with stainless steel pistons and brass sleeves for $320. It was worth the cost to me to know that they won't be stuck again! AL Bradley
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Randy Forbes:


And here's another long forgotten tip:
You can use Muriatic Acid to sharpen a dull file. The acid will etch those teeth back to a point.

<hr></blockquote>

Got to try that one. I was going to throw away all my old files. Now, where can I buy Muriatic acid?
 
Johnny: Muriatic acid is commonly used for heavy cleaning jobs, so look at places that stock contractor's supplies or swimming pool equipment and supplies. Both of these applications require the frequent use of muriatic acid. BE CAREFUL! AL Bradley
 
Back
Top