HA!  My 1990 Harley FX-S Lowrider came with DOT-5 too! AMF did that.  I still have it.

My idiot cousin had a Harley, he topped off with DOT-3 and the brake lines turned to goo.  What a mess THAT was... He let it sit for years and the gas turned to varnish.  What did he do?  Of course, he added new gas, opened the petcock, and tried to start it.  Carb was a mess after his buddies put the carb cables on wrong (and broke a few little parts).

So, two major problems.  Both soooo unnecessary.  Now, he hates Harley's.  Figures... he worked from GM.

Hey, y'know some guys put silicone fluids in EVERYTHING; tranny's, rear ends, you name it.  When they do, those components feel spongy too.  Silicone has its place, usually in racing because it can take heat.  IMHO, if you don't have temperature extremes, there is no advantage in using silicone (like buying premium gas for your lawnmower).

Rock Auto has Rabestos wheel cylinder rebuild kits for your car:
Front - $3.10
Rear - $3.54

I think they want ~$6/ea for the whole cylinder.  When I buy new ones, I always take them apart and inspect the iron.
One time in the '60s, I was doing brakes on a Pontiac.  I couldn't figure why the shoes didn't wear AT ALL on the back wheel after four years. I pulled the factory cylinder off.  Wouldn't you know, Bendix forgot to drill the oil hole throught the casting to the pistons.  That taught me a big lesson - use all your senses and check everything.

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

Thanks Dave,



New wheel cylinder cost me $12 at NAPA. At that price is seems silly to sand/hone & reuse leaky cups, especially since you have to take the shoes off to get to it. Old one really didn't look very corroded inside (I'm guessing...crappy chinese quality control).



Didn't realize 50s MC caps had a bladder valve (I thought that was just a baffle).



Most name brand DOT 3/DOT 4 on the shelves at discount stores say "synthetic" on the label.



My '90 1200 HARLEY SPORTSTER came with DOT 5. It's brakes were nothing to brag about. I think silicon gets spongy because it absorbs air.

6 VOLTS/POS. GRD. NW INDIANA

This might be why you're leaking:

Daniel, put a pan under your wheel cylinder, take the cups and pistons out, let it drain.  If the M/C cap is on, it won't drain much.  Use the discarded fluid to soak some 400-grit wet-or-dry sandpaper, and wrap a small strip around your finger.  Run it in and out of the leaky cylinder lightly.  Brake fluid on the sandpaper makes it cut better because the fluid prevents the little particles from loading the paper.  If you feel a ridge or obstruction, sand it out, wet-with brake fluid.  Inspect both piston cups carefully.  Don't be afraid to fold & distort them during inspection.  (Most of mine break at the flat part, around where the piston contacts.)  Also look at the edge for nicks or splits.  If the cups both look good, wash everything in fresh brake fluid, including the cylinder, and re-asssmble.  Bleed the system and test for an 'emergency stop'.  It should not leak.  You shouldn't need another flush for years.

DOT-3 and DOT-4 ARE compatable.  They are both the same viscosity and glycol-based, if you want to call that 'synthetic'.  Please consider why new cars come with DOT-3 (even expensive cars); it's still the best brake fluid, just maintain it every few years or so. You won't see any rust if you do (because it won't be saturated).

Other brake fluid types ARE NOT an option from the factory.  If DOT-5 was so great, and brakes are THE biggest safety issue, how come it doesn't come on luxury or any other car?  We're only talking a cup of fluid for the whole system.  DOT-5 is designed for extremely high heat racing applications, where DOT-3 would boil.  Being silicone-based, DOT-5 feels slightly 'spongy' because it compresses.

ALL M/C reservoir caps are vented.  They have a bladder inside, which separates atmosphere from the fluid.  Some look like bellows.  That gasket is very important.

DOT-5, silicone, doesn't absorb moisture.  Instead, moisture still enters around seals and pools in low places.  For this reason, ABS systems don't use it.

Hope this helps.  - Dave

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

Dave,



Still have original drum system. Finally have brakes broken-in/adjusted so car stops straight, so it figures replacing weepy wheel cylinder will likely upset everything.

Used synthetic DOT 4 last time. I wonder if synthetic brake fluid (like synthetic motor oil) more likely to leak?



Vented master cap makes weather rather moot. When original brake lines give up, I may consider DOT 5.



Went ahead and flushed/changed brake fluid to keep rust out of new cylinder, and will re-bleed after installation. Won't clamp the line, so no more crud can break loose (found a cork the right size for the brake hose). Will disassemble new cylinder and coat parts with brake fluid this time (may have installed last one dry).

6 VOLTS/POS. GRD. NW INDIANA

As Dave mentions, be sure to use only brake cleaner or alcohol to clean any brake fluid system related parts.  Any solvents that are used will be detrimental to rubber parts life.

 

As far as the moisture absorption that occurs with using Dot 3 fluid, I simply use Dot 5 fluids.  More pricey and does require some special care when switching over from Dot 3, but completely eliminates the sludge that occurs in the braking system over time due to moisture accumulation.

 

And here’s a link to a past discussion regarding Dot 5 brake fluid.

Silicone brake fluid 

Lorena, Texas (South of Waco)

Daniel, what swap?  Did you go from drum to disk?  Doesn't matter, both systems work exactly the same.  Believe it or not, ALL brake systems are open.  I'm going to start controversy here, but that's why DOT-3 sucks up water faster than Scotch Whiskey.  Every piston has seals that move, with air (full of water) on one side and DOT-3 brake fluid on the other.  They mix, but the fluid is 600-times more dense than air.

All brake fluid is clear when new, but after a few years in your system, old DOT-3 shows tell-tale red or brown color from rust.  How can it rust in a closed system?  It ain't that closed.  DOT-3 will saturate to a point, disbursing the moisture throughout the mix until it just can't hold any more water.  Saturated DOT-3 has a lower boiling point and a higher freezing point.  Both are bad.  Being in Indiana, you are familiar with high humidity and cold.  Imagine your brakes freezing!

Back in the day, owner's manuals never mentioned scheduled maintenance for brake fluid.  They certainly do now!  We're still using DOT-3 in new Fords because it is still the best (especially if your sytem is ABS), but now they want you to change it every 24,000 miles.  I do mine every few years just to make sure the bleeder valves work.  The whole system only takes about a cup of fluid.  Changing DOT-3 makes a lot of sense because it is glycol-based and it has rust inhibitors in it (like anti-freeze).

Leaky cylinders can just happen, usually when you first install them.  I have carefully sanded (honed) the ridge out of old cylinders using brake fluid, just to find three held like champs but one leaked.  Ok, I open the cylinder again and do exactly the same routine and it doesn't leak any more.  Whether it's your first or hundredth cylinder rebuild doesn't matter.  Usually if it doesn't leak at first, it won't later (provided you install new seals).

The biggest enemy is water, eating away inside the bores.  If pitting gets too bad, I just replace them.

Oh, a couple more things:
*  If it's raining out, I WILL NOT open my M/C reservoir lid.  That's how easily DOT-3 sucks up water.
*  Never use gasoline or oil anywhere near your brake parts.  Petroleum products bloat the seals.  When you put your brakes on, they won't retract and your wheels will be locked-up.
*  Never mix DOT-3 with DOT-5 brake fluids.  They turn to gel inside your lines, and most folks find it easier to replace all the lines, rather than try to clean them out.  The rule is, if your car came with DOT-3 stay with it.  The only advantage in using DOT-5 is if you are storing your classic car for many years.
Hope this helps.  - Dave

Royal Oak, Michigan (Four miles north of Detroit, and 12 miles NORTH of Windsor, Canada).  That's right, we're north of Canada.

Ford 292 Y-Block major overhaul by simplyconnected

The new front wheel cylinder I installed 2 years ago is weeping. Defective part (NAPA), or faulty installation procedure (first attempt)? Can anyone offer tips so I can be sure to do the next one right? Time to change fluid and bleed anyway. Aside from doing the swap in a bucket of brake fluid, what's the best way to keep air out of the system? I should likely change fluid & bleed entire system BEFORE the swap, to minimize any crud getting to the new cylinder?

6 VOLTS/POS. GRD. NW INDIANA