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Frozen Caliper Piston

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RJS

RJS

Jedi Warrior
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Hi

Had my right front caliper off today and discovered the outside caliper piston was stuck. The brake pad on that side was was worn about 1/8" inch more than all the others. Thus, explains the excessive brake dust I've been experiencing on that one wheel.

I was finally able to push it back in using a flat metal bar and a C-clamp (only after removing the caliper to get access). It required considerably more effort than a normally functioning caliper would required. I wasn't really able to diagnose what happened. Curious on opinions, what are the chances this is the end of my troubles (i.e. it simply jammed)? Or, is it more likely my troubles are deeper?

If deeper, I would most likely not rebuild myself. So, options would include sending out to be rebuilt or I see that one of the big three has new calipers for an extremely good price (slightly less than the cost of a rebuild!). Also I see stainless steel caliper pistons on the market. Any opinions on any of these options?

Last question, I will almost certainly install new brake pads. Car is used for gentle weekend cruises and low dust would be high on my list. Does anyone have experience with the Moss Premium Ceramic Pads by Classic Gold? They are pitched as "nearly dust free".

Thanks

Bob
 
Hey Bob,

If the caliper is that tight, it will need to be rebuilt. Once it all comes apart you will be able to tell what you are dealing with. With luck...it's just new seals. If there is corrosion and pitting in the caliper and/or piston, then it will take more work...and money in parts.

If you just jam a binding piston back in, it will not work properly. It has to be able to "float" in the bore or it will drag on one side of the brake disc...adding to your dust problem.

John
 
I ran into this with a MK3 Spitfire years ago. Both calipers were "frozen" from disuse. The car was not driven for a few years. In typical parsimonious fashion I stripped the calipers out. The bores responded to a liberal application of crocus cloth and I replaced the corroded pistons. New seals and pads and I was good to go. Never had another problem during 10 years of SCCA racing. Bob
 
The frozen caliper is a result of a corrosive reaction from the piston to the cylinder, caused by old/contaminated brake fluid. Probably water. After you unfreeze it, you are probably left with a ring of deposits inside the cylinder. That will surely contribute to rapid waring out the seals (rubber cups in the cylinder) very quickly. A complete rebuild is required and not that hard to do but replacement of the calipers is normally cheap enough to make it worth the added expense, unless you want the experience of DIY. I just replaced the calipers on the front of the XJS and happy with the result. I also had a frozen piston and the replacement calipers were only about $100 for the set. You should completely flush all the fluid from the system, including rear cylinders. Brake fluid is highly hydrophylic (water attractive), so use new, unopened brake fluid.
 
Personally, I'd be tempted to try working it back and forth a few times, to see if it loosens up once you get some fluid worked in between the cylinder and piston. If you were able to move it with just a C-clamp, it may not be corroded at all, just stuck. But if it doesn't free up, or starts to weep, then it's got to come apart (or be replaced).

On the TR calipers, the seal (just a square O-ring) rides on the piston, so corrosion in the caliper bore is usually not an issue. As long as you can get the piston and bleed valve out without actually breaking the casting, they are pretty much infinitely rebuildable.

Sorry, no experience with either new or having someone else rebuild them. And since I switched to DOT 5 fluid over 20 years ago, I've not had to rebuild my own.

PS, IMO the SS pistons are a waste of money. If you want good brakes, you have to either switch to DOT 5, or change the fluid regularly (like every 3 years whether the car is driven or not). If you do either of those things, the pistons won't corrode.
 
you are probable going to have to hook the caliper back up to the brake line, use a c clamp on the oposing piston to hold it in and pump the brakes to push the stuck piston out. Plan on doing that, you will never get it out otherwise. then see how bad the piston looks but probably a new seal kit and new piston

Hondo
 
Thanks,

PO rebuilt the calipers about 11 years ago just before I purchased car. New seals and pistons. Car has been driven about 9K miles since then. I had a garage bleed the brakes every 2 years before I took that over myself a few years ago. Perhaps they didn't actually bleed them...(?) I have noticed since I started bleeding my own the fluid is consistently clear!

Anyway, I'm thinking/hoping the piston was simply stuck. So, will try working it in and out several times and install a set of new ceramic pads.

After that, if I still have issues, I think I will opt to send them for rebuild. While I think I can handle a rebuild myself, there are two issues. 1) I have only a precious couple of hours in the garage per week, and 2) I don't want to mess around with brakes - I want to know it's been done and done right. Plus, parts to rebuild are about $55 per caliper and a rebuild costs about $115 each.

Thanks,

Bob
PS: still looking for any tips on dustless brake pads
 
RJS said:
<snip>
Bob
PS: still looking for any tips on dustless brake pads
Click to expand...

I have been using ceramic pads for about a year (Centric Posi-quiet; PN 105.033 for the TR6 or 105.00020 for TR4). No squealing, no dust and less than $30 for a two-wheel set. About the same stopping performance as traditional organic pads. I switched to ceramic after getting some alloy wheels and have yet to find any visible brake dust on my wheels.

Scott
 
I would strongly advise either rebuilding or replacing both calipers based on my personal experience.

My car ( Toyota) had a stuck piston in one caliper. I removed the caliper and used a C clamp to free the piston. The brakes worked fine for several weeks and sudddenly when the brake was applied the caliper locked and forced the car into the other lane. Steering control was lost as it veered into the other lane. I immediately replaced both calipers.


Please replace the calipers!!!!!!

Gerry
 
Excellent, thanks,

On the ceramic pads, I just realized the shop recently put Akebono ceramic pads on my '98 BMW M3 and ZERO dust. REALLY pleased and, no doubt, I am going for ceramics on the TR4A.

Thanks for the idea on the Toyota 4 pot calipers. If I drove the car more aggressively I would seriously consider. But, since I am watching the budget here, I'll wait on those. Very interesting to note I found NAPA Online has remanufactured calipers for $62 each, no core charge! "Protective coating, all mounting hardware, rubber parts coated with liquid preservative, precise lubrication, 100% pressure tested and guaranteed, castings heat cleaned and shot blasted..limited lifetime warranty."

I will say I have always been very impressed with the quality of NAPA parts (consistently very high) and I am very tempted here. I can barely rebuild my own for that price. Who knows, I might even go for the Brembo rotors they sell for $65 each.

Bob
 
Gerry,

Got it, thanks. I don't want to mess around.

One other thought, can you believe the local British garage wanted to charge me $225 per rebuilt caliper two years ago!!

Bob
 
Gerry's anecdote sounds frighteningly similar to my experience. Any recommendations as to a good rebuilder? Thanks
 
I'm not surprised at all about that quote from a specialist garage. Most will charge time and materials. Rebuilding the calipers is more time intensive than just R&Ring and some shops, especially if they are a restoration shop and do more than just a mechanical rebuild, they may also be cosmetically cleaning them up. If they have corrosion in the bores they could also be quoting you a price for splitting them open, completely cleaning them, installing new pistons and seals and don't forget the cost for brake fluid and labor for bleeding the system once the rebuilt calipers are back on.

Removing and replacing with new OEM style calipers and bleeding the system could be done in an hour or just over. Removing, splitting, cleaning, rebuilding, reinstalling and bleeding could easily exceed four hours for the pair, plus materials. Included in that level of rebuild should also be new bleed screws as well as a good cleaning of that area while apart.

Shops in my area range from $85-$100 an hour for general labor and that is for the British Specialists (they usually lower the rate for long term restoration work). Dealers and general mechanic shops can range higher (especially dealers). With those rates, and time involved that quote is not all that out of line. But you bring up a good point about if you have the ability to do it yourself, you can certainly save some money.
 
You'll need a bead blasting cabinet ,compressed air and a can of aerosol brake cleaner to do the job properly. Splitting the calipers , cleaning and re assembling : at least one hour. Two new pistons, new seals and bleed screw and you have $52 in parts alone. Just how well do you think the $62 calipers are rebuilt? $225 is probably on the high side. I would think $125 a piece could get them rebuilt properly, $62 can't. Depends on how much faith you need to have on your brakes !
 
So, three of the original brake pads had about 1/4" material left. The fourth had 1/8". This was after ~8,500 miles. No doubt, the one caliper piston was sticking.

I cycled that one piston back and forth several time successfully. It appears to move rather freely again. I installed Moss Ceramic pads this morning and bed them in properly. After a cool down drive, I immediately took the temp of both brake discs after pulling into the garage with an infrared. Both discs were 95 degrees F. I was pleased to find both discs exactly the same temp and the temp was (what I felt) reasonable (considering outside temp was 72 degrees). I jacked the font of the car and both front wheels spun freely with only a slight metallic "hissing" sound (I believe this is normal, correct?). So, given the disc temps and free wheeling, I am satisfied the one piston is no longer sticking.

I plan to monitor the disc temp and free-wheeling very closely over the next few drives. I may have solved the issue but, still considering purchase of rebuilt or remanufactured calipers soon. They are cheap and the stakes are too high not to.

Bob
PS: looking forward to clean wire wheels now with the ceramic pads!
 
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