Brake caliper question

37chief · Oct 7, 2017

I was looking for a couple calipers for my Ford 450. I decided it was cost effective to rebuild mine. Not too much to them. I ruined one using air to remove the pistons. I discovered 100 is too much air pressure. The piston shot out so fast it smashed the end. I ordered two more. I have one good one. The new pistons fall right into the hole, the other remaining good one goes in easy, but sticks slightly. My question is: do the pistons expand with age, and heat? I assume the piston should just fall into the bore, and come out easy, like the new ones. Any thoughts? stan

Arvin Haslem · Oct 7, 2017

If the new pistons fall in I have my doubts that they will seal. Measure the diameter of the new and old pistons.

da.bees · Oct 7, 2017

The sticking is likely caused by something that has stuck to both piston and inside bore. When contaminated ares come in contact with one another,it's enough to feel.

mite-help · Oct 7, 2017

yeah, I can see where a used piston with all the heat/cooling cycles plus varnish would feel different. without the rubber cups, as mentioned, measure

37chief · Oct 7, 2017

New pistons are .003 smaller. The bore has a rubber seal. In all my 60 years of twisting wrenches this is the first time I opened up a caliper. The reason I am dealing with them now is they are off my Ford E 450 motorhome chassis. Probably from not much use they stuck on. I thought my tranny was going out, as I was slowing down, no matter how much throttle I gave it. I stopped the brakes were smoking. after they cooled I was able to go again. Stan

JDEM · Oct 7, 2017

Metal pistons or plastic? Ford switched to plastic on many HD trucks back in the 90s, to keep brake fluid from boiling. Plastic pistons sometimes warp and get out of round.

37chief · Oct 7, 2017

Pistons are a plastic material. Stan

Mike M · Oct 7, 2017

Didn't you put a block of wood in there to catch the piston ? Make sure you hone the insides of the housing to clean it up.
Are those dual piston type ? Those are not easy to get apart. My F350 has those and after getting them apart the insides were too bad to reuse. Got remans from NAPA, I don't like those plastic pistons. pheolonic or something like that they call them. They seem to go bad faster than metal pistons ?

JDEM · Oct 7, 2017

The plastic pistons sometimes warp, get out of round, and stick. That might be why the new ones fit a little different then the old one. At one time, Dodge had big problems with the plastic pistons warping and sticking, and the "fix" at the time was to put in steel pistons. Ford went the other way. Ford trucks had trouble with the brake fluid boiling in front during hard braking. So the fix was to go to plastic that insulates better and transfers less heat from the brake pads.

Sean Feeney · Oct 7, 2017

replace rubber lines too

CKain(MI) · Oct 7, 2017

Seems to be a more common problem these days. I have repaired two 'family' vehicles recently, with sticking calipers.(and a bad hose).

olgentdc · Oct 7, 2017

GUYS , they just dont make them like they used to , my2000 lincoln had all the calipers replaced at least once ../BUT THIS IS THE TRUTH . last yr for the VERY 1st time since i owned my 69 Marquis convertible I changed the Front Disc Brake calipers,.. they were weeping brake fluid,,. still worked good , but i did not think there was any point in pushing my luck ,. i bought the Mercury used in 74 , drove it over 300,000 miles,. to over half the states in this wonderful USA ,. just a super sweet ride ..

37chief · Oct 7, 2017

After I smashed the first one into the caliper , I used blocks on the next one, but I will be replacing the pistons anyway. Stan

da.bees · Oct 8, 2017

" I thought my tranny was going out, as I was slowing down, no matter how much throttle I gave it. I stopped the brakes were smoking. after they cooled I was able to go again. Stan "

Old bugger might get a few more miles out of a gallon of gas without brakes dragging all the time.

504 · Oct 8, 2017

I am too lazy I guess,for $19.00 more than the seal kit, I can get loaded calipers and the hardware kit. Yea there would be freight on the cores, but still---

Hobo,NC · Oct 8, 2017

When you get them built stack wood clocks in the caliper apply air pressure to the caliper once you release the pressure it should also release the pressure on the block of wood. Stack it so you will have no more than 1/4 movement of the pistons. This also apply s to NEW/reman calipers if it sticks on the bench it will stick on the vehicle. Its not uncommon to find a reman sticking caliper I like to catch them now not later... Sometimes they will not completely release the pressure on the block it will be ok as long as you can remove the block without having to pry it out.

Its unbelievable the junk reman stuff that is out there. Even if all goes well check for excessive heat after a test drive and that the vehicle rolls free when you release the brakes. My Rockauto rant never again will I buy are install a part form them WHY who are you going to call if you have a issue its all email and takes days to resolve...

jimg.allentown · Oct 8, 2017

There is no reason to hone the insides of the housing. There is only one small sealing surface in the housing. Inside where the square cut o-ring goes, it seals on the back side of that bore. The rest of the housing is just a fluid chamber. The important part is the outside of the piston. That is the part that moves against the seal when brakes are applied or released.

GarryinNC · Oct 8, 2017

There is good chance that the rubber brake hoses are causing the problem. They seem to collapse where the clamp is that attaches hose to the A-Arm. When you apply brakes, the pressure is high enough to push fluid past the restriction, when you release brakes, the pressure is trapped between restriction and caliper. If you can crack bleeder screw and brakes releases, it is the hose, if no release, then caliper sticking.

Replaced hose last month on my 1990 1500 Chevy.

Garry

Hobo,NC · Oct 8, 2017

If you can afford a caliper you can afford a hose that's my story and I am sticking to it..

JML755 · Oct 9, 2017

(quoted from post at 22:09:27 10/08/17)
If you can afford a caliper you can afford a hose that's my story and I am sticking to it..

I agree but... be prepared for a longer repair job, especially on an older vehicle. Just did the brakes all around on my '04 F150. Pistons were cracked on 2 of the calipers, they were metal, not plastic. Bought rotors, pads, calipers and hoses. (Also replaced the parking brakes. One of them came off in pieces and the actuators were rusted up solid, wouldn't budge) Totaled about $600 or so. Did fronts a couple of weeks ago, did rears this weekend. The hoses came off pretty easy on the front. The rears were a different story. Couldn't break the hose fitting loose from steel brake line. Ended up taking the steel line off and working on it in a vise in my shop. PBBlastered the sucker, used heat, nothing. Started to round off the fittings so I just went and got a new $2 fitting for the steel brake line but what a pita. Ended up spending about 2 hrs extra messing with one side, so I left the hose on the other as I was running out of time with the missus looking out the door as we were supposed to go somewhere. Kept the new hose so some day when I've got some time, I'll replace it.

Brake caliper question

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