How to remove pistons from front brake wheel cylinders

[shadetree 5,543]

Ah yes, those dreaded wheel cylinders on front brakes !. we all know, or have been there ?, how they seize up over time, and now you dont have front brakes !. well, I am tearing this '88 trx350D foreman 4x4 down, and currently going through the front brakes, there was none !..lol. brake shoes did not look like they have ever been changed/serviced ?, so here is a nice little break down, step by step on how to free the wheel cylinders , free the star wheels up, and clean the bore out of the wheel cylinders.

 

Mind you, this is for old school front drum brakes !. first picture is the front brake backing plate, as you can see, the shoes are done !. remove the brake line from the wheel cylinder, takes a 12mm wrench, remove both sides. inside the shoe area are 4 bolts, these are 12mm as well, remove them. carefully , with a rubber mallet, hammer the backing plate off the knuckle. take the backing plate over to a good work area. I am listing pictures as I go, I used a 1/4 fine thread zerk ( grease fitting ) in one hole, while using a bolt ( metric ) in the other hole to plug the wheel cylinder up, so my grease gun can press the piston out of the bore, make sure to pry the rubber boots up off the lip, so they wont tear when the piston starts to move out of the bore.

 

once the piston is out, I carefully use my bench grinder that has a fine wire wheel to polish the grime off the pistons. then I use my Dremel with the cupped wire wheel to polish the inside of the wheel cylinder bore to remove all that built up gunk. I then take the star wheels to my bench vise, as you can see in the picture how I clamped the vise grips over/around the brake shoe slot , DO NOT USE THE VISE GRIPS AROUND THE TALL SIDES !!!, or you will snap them off, and then they are junk. 

 

NOTE: these star wheels have left hand threads, and right hand threads !!!, make sure you notice which side has what ?, and do not get them mixed up !. also the wheel cylinders ( if you clean then up ! ) has markings on them, L and R, right hand side uses left hand threaded star wheels, left hand side uses right hand threaded star wheels.

 

 

Edited January 20, 2020 by retro
Exported back to thread

[bcsman 1,345]

Man that's some ugly looking parts before cleaing up...

 

Thanks for the post I'm sure it will help out some here including me when I get around to this..

[shadetree 5,543]

4 minutes ago, bcsman said:

Man that's some ugly looking parts before cleaing up...

 

Thanks for the post I'm sure it will help out some here including me when I get around to this..

yeah, they were a tad nasty !..lol.

[Mac102004 424]

This is how I do it too, unless I can find cheap complete wheel cylinders in good shape. The rebuild kits for them are pretty expensive, to the point it can be hardly worth the trouble.

[toodeep 1,732]

I use to have an old master cylinder rigged up to force them out using brake fluid.  The grease would work a lot better when the seals are out. 

 

 

[shadetree 5,543]

48 minutes ago, toodeep said:

I use to have an old master cylinder rigged up to force them out using brake fluid.  The grease would work a lot better when the seals are out. 

 

 

I've tried it with brake pressure, for some reason brake fluid does not have enough psi compared to grease psi when your dealing with old seized stuck wheel cylinder pistons that have never been serviced. grease seems tp work very well for me.

[retro 3,870]

Boiling the wheel cylinders in water before pumping the pistons out helps too.

[Fishfiles 19,670]

A good grease gun will put out 10,000 psi ------ try soaking them in vinegar first , amazing how well it dissolves rust 

[Mac102004 424]

That’s because the pressure you can exert with a grease gun is enormous in comparison to what the master cylinder can out out. Now I’ll admit that I do not know what kind of pressure the master cylinder IS capable of, but last I checked a grease gun has the potential to exert 5000-10,000 PSI. I think if it takes anywhere near that much though you should think about chucking the wheel cylinders in the trash haha

[Fishfiles 19,670]

I think the trash is the best place for any condition wheel cylinder , cause if it don't look bad at the moment , it is soon gonna ----disc conversion when available is the way to go 

[TBRider 1,391]

I'd toss em out too, I can get new ones for 10-15 bucks a piece for my old king quad.

[toodeep 1,732]

I agree, disk brakes are way better. If they are not mud machines the drums can work good. I have some that come in that look like new yet on the inside and they are 20 years old. I just worked on a 84 trx200 and the brakes still had the shine on the inside, the outer of the machine not so much.

[Mac102004 424]

11 hours ago, TBRider said:

I'd toss em out too, I can get new ones for 10-15 bucks a piece for my old king quad.

 

You should price them for a Honda lol 🤮

[Mac102004 424]

10 hours ago, toodeep said:

I agree, disk brakes are way better. If they are not mud machines the drums can work good. I have some that come in that look like new yet on the inside and they are 20 years old. I just worked on a 84 trx200 and the brakes still had the shine on the inside, the outer of the machine not so much.

 

It's true, I've never replaced the pads on my 350 Rancher and they still work, I need to adjust them again, or maybe check the pads....lol 16,000+km on it now. Not a mud machine, just an old farm quad.

[TBRider 1,391]

23 minutes ago, Mac102004 said:

 

You should price them for a Honda lol 🤮

I priced mine for the kq at the local dealer and they told me they were $127.00 each. But I managed to cross reference the same part to a suzuki swift and a geo tracker, same part on both but the car part was 15 bucks...lol

[Mac102004 424]

31 minutes ago, TBRider said:

I priced mine for the kq at the local dealer and they told me they were $127.00 each. But I managed to cross reference the same part to a suzuki swift and a geo tracker, same part on both but the car part was 15 bucks...lol

 

LOL. Got lucky there man.

[Howols 11]

Another tip is that a Dorman 351556 wheel cylinder kit (cups and dust boots) fits pretty much every TRX350-650, 86 and up that uses drum brakes. Can be had for about $3.99 per wheel. Works perfect.

[retro 3,870]

6 hours ago, Howols said:

Dorman 351556 wheel cylinder kit

 

Thanks for the tip! Got 4 of 'em on the way from rockauto cheap!

[Mac102004 424]

Yes good to know, I've used the brake panels and all from the larger models on the 300's as well, so swapping the whole thing to get the cheap brake parts shouldn't be an issue.

[TBRider 1,391]

The front cylinder for the 99 kq is a Dorman #W37850