On my 91' f250 I'm having an issue with the metal piston like thinks that insert into the wheel cylinder on the drum brakes. They are corroded and pitted. Resulting in a incomplete seal, non working brakes, and leaking. Does anyone know what these are called? or even if you can buy replacements? The wheel cylinders were replaced not to long ago and this issue started.

 

It is the piston. I think you can get a rebuild kit for wheel cylinders, but they arent expensive. You said they were replaced not too long ago so I dont know what else to tell you. Buy new or rebuild.

 

Called a slave or brake cylinder,



As suggested yea just replace it as a complete unit, only cost about 20 bucks, get fresh bleeders that way too!

Be sure a replace the brake shoes, shoes contaminated with brake fluid can not be cleaned, use brake cleaner on the drums to flush the fluid off them.

 

If you are talking about the rod that fits in the wheel cylinder and hooks to the brake shoe, that has nothing to do with leakage. If you pull back the w/cyl dust cover and brake fluid runs out the wheel cyl cup is leaking. If the piston itself is corroded you might as well get a new PAIR of wheel cylinders. They are cheap enough and you won't have to worry about broken bleeder screws.

 

what your talking about is the WHEEL CYLINDERS , if they where replaced then you got cheated as the ones you are describing are warn out ! WHAT YOU NED TO DO IS GET SOMEONE THAT YOU CAN TRUST AND WATCH THEM AS THEY REPLACE THEM , YOU MAKE SURE YOU ARE WITH THEM WHEN THEY ARE BOUGHT ! new one will fix your problem as the individual pieces are not available by them self's !!



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I replaced them myself, well me and my dad. NAPA parts about two months ago. I really think it is the metal inserts, i guess since no one knows what they are. I'll just grind them down so they are smooth. They have tons of scale on them and arn't even close to smooth. If that doesn't work i'll go ahead and do the disk brake conversion. Drums are a pain in the ***.

 

Yea I'd agree with that for sure, if you just paid someone not long ago to replace the wheel cylinders, take it back.

Tell em to do it right this time, actually install new cylinders.

Takes years for the pistons to corrode/develop pitting, not something that happens in a few months. Even with nasty brake fluid.
And if the fluid was that bad it should have been flushed after the cylinders where replaced. Not hard to do, fifteen extra minutes work if that at that point....if they took their time at it.

 

If you are talking about the little rods that go between the shoe and the wheel cylinder I would describe them a the brake shoe strut. However as already stated they have nothing to do with fluid leaks.

 

It could leak if they don't seal well and pull the seal on the cylinder off. I think thats what its doing. I have to change the brake fluid anyway as there is very little left. This was / is a plow truck so its a bit beat up. Lines are all brand new tho. Its in this drum.

 

The metal piston isn't what seals-it's the rubber cup BEHIND the piston. If the pistons are that bad, probably the bore in the cylinder is bad too, and that's why they're leaking. Return them & get some new ones.

 

the plunger has nothing to do with leakage from the cylinder, all it does is ride in a "dimple" on the end of the wheel cylinder piston....
if you have leakage, its cause of a pitted/wore bore, or piston in the cylinder....
i just totally rebuilt a posi rearend for my truck so i took a crash course in brakes and related parts...

the rubber dust cap that the plunger goes through is just that, a dust cap

sounds to me you need new wheel cylinders, but beware.....you WILL NOT get new plungers with new cylinders...

but you can get replacement plungers from advance....just take an old on in to match up the length.... about 6 bucks each for the plungers at advance, and i think 16 bucks each for new cylinders from oriellys, oriellys wont have the plungers, and no way to order them.... have to go to advance for them
if you do it yourself, will take about 1/2 hour per side if you take time and clean everything while in there.....new spring kits would be a good idea also, especially for a plow truck..... around 7 bucks per side for the new spring kits

 

Thank guys for the help and actually telling me what the part was. I probably damaged the new wheel cylinder on that side instead of saying bring it back to who ever put it in when i said i put them in.

 

I had to replace the plungers on one side when I got my pickup because the originals had gotten lost. Like said above, they don't seal anything. If you look at the rubber boots on the cylinder they just have a notch in the middle for the plungers to fit. I got mine from Napa.

At least the cylinders are easy to change out and pretty inexpensive.