sticking front brakes

[Ken Talbot]

When I have used air, the pistons popped out with probably no more that 10 pounds, but my pistons were not seized like it sounds your are. I would try twisting each piston with a large plier like TC says just to break them loose. Then a puff of air should do the trick.

[AlanB]

Hi Guys,

Take care with the air; I shifted a seized piston that way a few years ago. It took 155 psi and managed to send the piston out through an asbestos roof. Unfortunately, it took a chunk of the bone from my thumb-joint with it............

It is much safer to use something non-compressable. Grease is bad for the rubber; the easiest and best is just to leave it all connected and pump the piston out with the master cylinder.

That way, there is nothing in contact apart from brake-fluid; And no exploding pistons!

AlanB

[John]

Grease

The grease I have access to is molybdenum, and I haven't had any adverse affect with contact with the square ring in the caliper. I don't leave the grease in the caliper very long. and I take care to clean the ring, caliper and piston very well. sometimes the M/C are so worn that they cannot generate enough pressure to force the piston out of the caliper. I have had more problems with the rubber pieces deforming/swelling from the use of Brake Clean, than with the use of grease.

[HobbyMan]

Here is the deal, If you can get it to move out a little bit, you can tap it back in. You keep pushing it out with air as far as it will go with reasonable air and push it back in. Eventually it will come out without endangering you. I still suggest putting a rag in fron of the piston to absorb the shock and residual brake fluid. I don't like wasting grease, though that may work.

[KJK]

I had successes removing the piston with a few of your ideas.

The right side required penetrating oil, time, large pliers to twist it just a little, a heat gun (wife’s hair dryer), and 50 ponds of compressed air. I had a shop rag stuffed in to catch the piston, and do not recommend more pressure than that.

The left side received the above action, but could not get it out. Reattached the master cylinder and moved a hose to it. After a little air bleeding, the piston began to move out very slowly. This does take a long time but is very effective on corroded calipers as these are.

The “square o-ring” makes sense now. One of them has dried fluid on it, and I’m wondering if they are resilient enough to clean and reuse? They seem to be very stout.

The pistons are easy to clean but the calipers are a little more time consuming. I think some fluid and a green scrubby should help knock off the dried up fluid from the caliper.

The hoses look to be in good shape, but I should clean out the inside because of what I seen above and below them. Any ideas on how to make sure I don’t have any jelled or bad fluid in them?

I started this brake project because the front master cylinder was leaking at the plunger as well as an occasional sticky front brake. Very glad I pulled the calipers apart also.

STEPPENWOLF, You can do it!!

Kevin

[HobbyMan]

Take your air gun and blow out the lines with compressed air. That is what I usually do. I have a rubber tip on my air gun that I push in one side of the brake fitting and I squeze my thumb over the other end. Just use your imaginaion. Most everything will come out

[TopCatGr58]

Congrats KJK,

Now, for the brake lines, I used several strands of wire wound together, but still small enough to fit inside the hole of the hose, and fed it thru the hose, pulled it out the other end, but had it long enough to stick out both ends, then I could twist it around to act like a roto rooter snake to scrub the inside of the hose. I used (again in my ignorant youth) some spray carb cleaner, but perhaps brake clean cleaner would be better? Squirted inside the hose, scrubbed, squirted again, and then removed the wire, and squirted in again, then swung it around to clear it out, but compressed air would be better!

The square O-ring is pretty strong, just clean with your fingernail to scrape of the crud, inspect the edges for rounding off or such. Also clean out the channel it sits in, I used a dull knife edge, or a straight screwdriver edge, etc. on the channel!
T.C.

[prometheus578]

I use the compressed air method, as I've done it for years. Yes, it is quicker, but extremely tricky... As mentioned earlier, there is the potential, when the piston finally pops, to really go flyin'. I'm not serious on this site too often, but about this, I am. If done carelessly...you'll never want to do it again... (and maybe won't have the fingers left to try)
Pumping it out using the master is a far safer way. Just keep refilling the resevoir.
Before removing the bolt at the banjo fitting, have two thin peices of wood, and a "pre-adjusted" visegrips at the ready.
Remove the bolt, sandwich the hose fitting between the pieces of wood, and clamp the thing with the visegrips. This stops the brake fluid from the resevoir from draining out the hose while you work.

[papanovember]

I rebuilt my brakes earlier this month. I used compressed air to pop the pistons out. I filled a five gallon bucket with old rags, placed the caliper in there and popped it out. It will not fly through your garage wall and the rags soak any brake fluid left in there.

[STEPPENWOLF]

I have not had the time to dig into this project like I thought I would. What little time I had, I spent on the bike trying to correct the slow turn signals. Today I just rode the bike,brakes were free since I cleaned the spooge hole,every thing felt good:-)I still want to do the calipers tho. Per another thread..I put Seafoam in the tank..........after the smoking...as stated...tune up in a can!!!! something that really works!!!!27 year old carbs are acting like a 18 year old on his first date:-)Head out on the highway!!!!!!!!!!!!Wheeelie time.....

[adleeman]

Update-2/09

the hair dryer trick works very well