Gelled brake fluid in caliper - looking for rebuild kits

[Guest]

Just bled the 29 year old fluid out of my front brake this weekend and it looked like coffee, with grounds and everything. I have gotten a replacement master cylinder/brake line, and want to rebuild the caliper. Does anyone have a good source for piston seals/boots for a caliper rebuild? I have gotten a quote for factory replacements of about 20 bucks for a boot and seal, but thought i'd ask around before buying. anybody dealt with gelled fluid in a caliper? was it a pain to repair? anything i should be wary of?

1980 GS450L with factory single caliper on the left front.

thanks
mike

[Nessism]

Z1 sells inferior K&L brake parts. OEM Suzuki seals are far better quality. There are a bazillon threads in the archives on where to purchase OEM parts so I'll skip that part.

[chuck hahn]

Some things to be warry of.

1...The psiton isnt gonna come out easily. Remove the caliper, close down the bleeder valve, keep your finger AWAY from the front of the piston, stick an air hose TIGHT against the banjo bolt hole and watch to see if the piston is moving. May be very slow. If not moving at all, then apply a little heat to the piston to warm up the seals rubber, a good dose of PB Blaster and retry.

2.. The groove the seal fits in will most limkely be full of chalky grey scale...this must all be removed and as clean as you can get it.

3..Lube the seal with brake fluid before installation and run your finger around it a few times to kinda settle it into the groove decently.

4..To clean the bleeder and get it as rust free in the lassages, heat it up real good with a propane torch and plunge it in water..repeat a few times. The heat / quench cycles will breakm up any rust and scale inside. Spray it out with some carb spray and then fry it well with air.

5..The splitter valve ( if equipped with ) will neeed cleaned out as well.

6..Use new crush washers at all joints.

[BentRod]

Agree with most of the above, but I would skip the heat to clean passages. The calipers are aluminum, and while they are great conductors, the thickness makes thermal shocking a little of the risky side. Not that it shouldn't work, it's just.. well.. a 29 year old caliper. It will be rust or other oxides inside the passages, so a good soaking in any acidic fluid will work, such as white vinegar or CLR type product. Don't go over board and use strong acids as they will attack the aluminum caliper itself. If you must scrape or poke at it to clean it, use plastic tools, or soft tin. do not use brass or copper.

Seals and boots. I used the OEM parts, but most kits should be ok. Just ask and make sure they are ok for use with the brake fluid you intend on using. Most DOT4 fluid parts are fine with DOT3 fluid, but not all.

Things to be wary of. Any moisture what so ever during the rebuild will cause problems down the line, so rinse and blow dry with gentle heat. I recommend generously covering all the interior surfaces with blake fluid before you start assembly. You can wipe off excess from the body with a clean rag, but do not bother wiping anywhere on the interior. I also recommend completely flushing the system a few weeks after the rebuild, to get any moisture that may have made it in and mixed with the fluid out of there.

Be mindful of the cylinder walls. The aluminum in calipers is on the tough side, NOT the hard side of the alloy family. It will take a lot of abuse to break it, but not too much to scratch up the cylinder.

Other than that, as already said, use new parts including new crush washers, and it should be an easy rebuild.

you don't have an anti dive system do you?

[chuck hahn]

Not the caliper bodies Bro....take the bleeders OUT and heat and quench just them...it works better and easier than anything Ive ver done before.

[chuck hahn]

I dont think he wamnts to wait a week by using vinegar or CLR to clean the scale out of the groove. And as far as your brass or copper brushing goes..I use the little wire wheel in the dremel and of the hundreds of calipers ive rebuilt not a single one has ever leaked as much as 1 drop. If he isnt worried about the paint and plans on repainting the bodies, then an overnight in the Berrymans will do the trick also and faster as far as a chemical approach goes.

[Nessism]

Seals and boots. I used the OEM parts, but most kits should be ok. Just ask and make sure they are ok for use with the brake fluid you intend on using. Most DOT4 fluid parts are fine with DOT3 fluid, but not all.

I also recommend completely flushing the system a few weeks after the rebuild, to get any moisture that may have made it in and mixed with the fluid out of there.

Aftermarket brake system parts suck. I've had two bad experiences with K&L parts, and others here have too. They are no cheaper than OEM parts anyway so why bother?

As for asking whether or not aftermarket parts are compatible with your brake fluid of choice, who do you suggest asking? The retailer? I doubt their is any risk there regardless, just questioning your suggestion.

And who has ever flushed out their rebuilt system after a few weeks? I don't. OEM car and motorcycle companies don't either. Unless you are rebuilding the system in a driving rain storm there is no risk there either.

[MOC]

Just ordered some OEM replacements from a local shop for 10 bucks. regarding the fluid type, I'm assuming that OEM replacements will tolerate the stock DOT3/4 fluid that i've got.

as far as removing the cylinder, i don't have an air compressor, so what would be the best way to do it? I've got plenty of brake fluid, so perhaps just keep pumping on the brake handle until that sucker pops out? might dislodge some of the crap in the process

i've managed to free up the piston by bleeding and flushing with fresh fluid 3 times, so i'm not worried about it sticking. I also have no problem sticking the calipers in a solvent bath for a few days before rebuilding, as the bike isn't on the road yet. i DO plan on repainting the bodies. they have peeled over their 30+ year lifetime, and I picked up some of that high temp engine block paint from autozone for when all is said and done.

thanks as usual for the feedback. this is my first bike, and it's a lot less daunting with your help.

[chuck hahn]

Only thing the 3 or 4 means is its heat applicable rating ( brake heat created when applied friction form the pads is tranfered to the fluid). Either 3 or 4 will be more than youll need unless your drag racing it all day long at the track.

[chuck hahn]

Some have put a regular bolt in the bajo bolt hole and pumped grease into the bleeder nipple with a grease gun. Pumping the handle will work on single disc setups, but soon as one or the other comes out youll still need to deal with caliper number two somehow.

[Nessism]

Just use brake fluid pressure to push the piston out. A little messy but no big deal.

[MOC]

I figured as much, it's a single disc, so i should be ok. thanks for the help fellas.

Some have put a regular bolt in the bajo bolt hole and pumped grease into the bleeder nipple with a grease gun. Pumping the handle will work on single disc setups, but soon as one or the other comes out youll still need to deal with caliper number two somehow.

[BentRod]

I agree with OEM parts. It's all I really trust for the extra cost.

As to the brushes and chemical dipping, I will stand by my advice, although I recognize that it is absolutly possible to do the same job with a brass brush, it just really comes down to who is using it. this is espcially true given that the seal is actualy provided by the rubber o-ring and the piston wall, and not the aluminum body of the caliper. Still, gentle acidic baths tend to be easier for a first time restoration, and the o-ring groove is where you are most likely to need to do some brushing, so I advise caution. Same deal on bleeding the system. Yes, it is normally not done, and it will probably achieve very little. I do it anyways... may be it's just superstition

two note for future reference:

1) if you have to get a second piston out, when the first one is almost out, brace it so it cannot come otu any more. You can do this with a correctly sized C-clamp.

2) Dot 4 fluid is really not good for DOT 3 components. Particularly they tend to soften the rubber walls in brake lines.

[Nessism]

2) Dot 4 fluid is really not good for DOT 3 components. Particularly they tend to soften the rubber walls in brake lines.

Sorry to be a jerk and all but this is not true. Dot 3 and 4 are almost identical fluid, only 4 has a higher boiling point. 4 has all but obsoleted 3 in the US, other than some auto parts stores stock the 3 as discount fluid under obscure brand names or even house brands.

[spyug]

I don't see it mentioned, but about 80% of the time, IMHE, the pistons are damaged by cracks or pits in the chrome on the piston skirt. This can be dangerous as it can allow moisture over time to form rust causing the piston to jam in the bore. I've had 2 rear calipers that were jammed due to this.

If you find the piston like this, it should be replaced for safety sake.

With brakes you can't fart around, you life can depend on them.

Good luck,
Spyug