1B.DZ

Alright guys, I've been searching for some procedures and can only find talks of this. I need to flush my entire system, but don't know how to do it. I have an air compressor and can get a drier to keep the water out. I have S/S braided hoses and Quick bleeders to install. After searching and reading a few posters have put up different sequences to bleed the entire system with. Which one is right?

I get that for each caliper I bleed the bleeder closes to the hose first then the outer one, but not sure on which calipers to do in what order. First though, I need to know how to flush the entire sytem of brake fluid. I'm pretty sure mine is contaminated. Can I unscrew a brake line from my MC and hook up the air compressor with the bleeder screws open and then do the other line? I read something about a steel plate on top of the MC, but am not sure how that would work. Does anybody have any pictures or diagrahms I could possible carouse over? Thanks for all the help I have received on my brake system so far. I can only expect some good answers and discussion from this.

TIA

Josh

genuine1980

Here is how I got the old contaminated stuff out of my system... was a one man operation and seems to have done the job right.

I think you said you have the tool that you hook up to your air compressor, and it sucks the fluid from the bleeder screws... I also have this tool.

Open the master cyl and get all of the old fluid out of it... use a turkey bastor or something. Use a clean rag and wipe the inside to get any crap out. Now fill the master cyl with fresh brake fluid, and use you sucking tool on the caliper bleeder screws to suck the old fluid out of the lines and the new fluid from the master cyl into the lines. Careful not to run out of fluid in the master cyl as you will suck air into the lines. Repeat the process on each caliper until the fluid you are sucking appears the be the good new fluid and no old crap is coming out. This method also gets the old crap out of the caliper cylinders. I don't remember in which order you need to do the calipers, but I'm sure someone else will chime in.

DJ Dep

If you've searched as you say, then you've probably seen the posts about the Motive Pressurized brake bleeder. It's probably the easiest and best way to flush a brake system. No need to drain the master cylinder. Just clamp it on top and pump it up (hand pump is EASY) and it forces new brake fluid into the master and through the whole system as you bleed each wheel. Ask anyone who has one...they'll all say it's the best investment they ever made in brake tools

http://www.motiveproducts.com/index.html

Dep

1B.DZ

I may have to find that tool. The tool I was refering to apparently takes the water out of the compressed air. Somebody mentioned it in another brake thread of mine. Where can I find the tool you refer to? I'm replacing all hoses, so is it OK just to suck all the fluid out of the lines and calipers and then hook everything up and repeat process, but keeping the MC filled this time? It will basically be a one man operation, but my dad will try and help, he said he will check out my PS pump-it's leaking.

Josh

1B.DZ

I have seen those posts and haven't had any luck with power bleeders and what not. I bought the little vaccum pump one and it never worked. I'd hate to go and buy another tool when I can use my Air compressor.

Josh

GaryS

Well, perhaps you can call me old fashioned AND cheap! I take my wife's turkey baster (YEP!) and suck out all of the old fluid in the MC. PLEASE BE CAREFUL and cover your fender. If brake fluid touches the paint for even a second you will have damage. I then fill the MC with fresh, clean fluid and loosely place the cap on. I go to the right rear caliper and have a helper pump and hold the brakes. I then release one bleeder and then close it. I do this to both bleeders on the rear until the fluid comes out clean. I know that this line now has fresh braek fluid in it. I then go the LR followed by the RF and LF. After each bleeder is done, I refill the MC so that I don't have to worry about air getting into the system.

No special tools, no special techniques but it has worked for me for years. If you choose to use the Motive Power Bleeder, use their website to order the correct one:
http://www.motiveproducts.com/02bleeders.html
I have no personal history with this product but I have read good things about it.

Gary

1B.DZ

That makes sense to me. As far as installing the S/S braided lines go...Do I change both back or front lines at the same time or do I have to change both right side or left side at the same time? Or does it even matter?

Thanks,

Josh

KapsSA

I'll agree with using the Motive Pressure Bleeder. I have 4 Vettes and I flush 1 brake system each year. Couldn't be easier. If just flushing to remove contaminates, no air in the system, it doesn't matter the sequence you flush. I push about a pop can of fluid out each bleeder. With the Vette up and tires off takes maybe 15 minutes.
If in doubt, the correct bleeding sequence for Corvettes is...LR-inner, LR-outer, RR-inner, RR-outer, LF, RF. This IS contrary to bleeding order on most other cars(furthest from master first, nearest last) but IS correct for Corvettes.
Mike

S489

the only way to completely flush the system clean is to take it apart; this includes the MS and calipers. the only pressure bleeder that has worked for me was has been a diaphragm type. if using a pressure bleeder, you can use a tool to push each of the caliper pistons full back into their bore to eject as much residual fluid as possible. this will take a number of times on each piston. in the end, there will still be some "contamination", but will be as little as possible without dissasembly. unless you happen to be mixing incompatible fluids, this shouldn't be an issue, e.g., if mixing (swapping from) dot 3 to dot 5, the fluids are not "incompatible", they just don't mix. in this case, you don't want the dot 3 to find its way behind the piston seals. if using dot 3 or 4, the "contaminated" fluid left in the system will dilute itself throughout the system (this is good).

DJ Dep

good info!!!!

F4 Woozzo

I have to agree with the folks using the Motive pressure bleeder. I've used it on my C3, C5 (twice), and Subaru. When club members saw how easy it was, I loaned it out and it's done probably 4 other C3s in the past year. No tricks to using it - very easy, very quick, one person job.

Just make sure to get a good seal on the master by doing a dry pressure test first - pump it up to see if it holds pressure. If it does, release the pressure, add plenty of clean fluid, repress and you're off... Sequence listed above.

If you use clear tubing on the caliper bleed ports and a clear catch bottle you will see the cruddy fluid coming out. Brake fluid is cheap and with this method you can run enough through each caliper in very little time to be sure it's cleaned out. Nobody's leg gets tired pumping and holding the pedal, you're not constantly opening and closing the bleeder, and you don't screw up the sequence and suck air into the lines. Convinced?

DJ Dep

F4: I switched from using that chain gizmo to using two C-clamps. Much better seal with them!

1B.DZ

Thanks for the info guys. Hopefully I can get all I need done on Sunday without any hitches, which always come up when I work on this car.

Thanks,

Josh

Tom454

Here is some more info I have in a .doc

I used to own & operate my own 7 bay repair/machine shop (NJ) so I was able to try a lot of different techniques. I also had a shop in NY State before the 7 bay shop in NJ.

The C2/C3 brake system is not all that complicated relative to other designs.

Once you understand the "physics" of the system, the BS ends.

I actually enjoy doing C3 brakes.... it's so easy.

First, anyone who tells you the order is important doesn't understand hydraulics.

There is no difference in the order in which the calipers are bled... regardless of what they say. I did an experiment to prove this specifically for forum members a while back.
I repeatedly opened up lines on my own C3 and drained them, and re-bled the system in random order. There was absolutely no difference in system performance based on the order of bleed. So don't get hung up on order... it is irrelevant.

I knew the answer to this question before I even started the experiment due to the enormous quantity and variety of brake jobs I did in my shop.

For example, when doing NY State Vehicle inspections, in order to prevent shops from gouging people at inspection time, you are required by law to fix only things that are broken or are a safety issue. So, when a single wheel cylinder (or caliper) was leaking, you had to fix ONLY that one item.... not all four. Although bleeding all 4 is good practice, this meant you had to bleed only that one item if the rest were okay. This is what was done... and the cars brakes all worked fine after the work was complete.

C2/C3 Corvette calipers are composed of two halves. If you bleed the half FARTHEST away from the hose/line connection first, and then the half CLOSEST to the hose connection, then you can re-introduce air back into the caliper-half farthest from the hose connection. So when bleeding an individual caliper, it is important to bleed the caliper half closest to the hose/line (the inner half) connection first.

Remember this concept instead of left inner right outer right inner left outer right outer blah blah blah etc. It's much easier just to understand the principle as explained above, and you do not have to follow any memorized "order".

Recap…. M/C first, then any caliper, but inner half first.

The M/C (master cylinder) always has to be first because any air in or around the M/C is forced "downstream" where it causes problems.

The first objective is to remove all of the air in the M/C.

To (bench) bleed the M/C, you need fittings & tubes to route the fluid from the exit ports back into the reservoir on top. These used to come with a new/rebuilt M/C, but you can make your own by buying short pieces of brake line and bending it.
Install the tubes & press the M/C piston (pedal) until you get a solid, bubble free flow all around. The M/C is mounted at an angle in the car… air bubbles can get trapped in the highest point of the bore… so try to tilt it to “level” the playing field.
With DOT5, just go nice & slow & steady and you will not generate the tiny bubbles that DOT5 is famous for.

To test the M/C at this point, remove the tubes and replace them with inverted flare plugs, being careful not to allow more than a few drops of fluid to run out of the ports when you switch over to plugs from tubes.

The ports on the M/C are inverted flare, and you can either buy or make inverted flare plugs for them. To make your own, buy brake line with the correct inverted flare fitting, cut them off about 2 inches from the end, use a hammer to flatten the tubing for about 1 inch opposite the fitting end.


Again press the piston (pedal). The M/C should be hard as a rock.
If not, there is still air in the passages, or the internal seals are bad, or in some cases, the piston & seals assembly is put together wrong... I have seen this on new M/C’s.

Once the M/C is finished, it's time to bleed the lines & calipers.

If you have a brake switch (AKA proportion valve), it can cause problems at this point.
Some C2’s did not come with a switch/valve. I believe all C3’s did.

A good, properly functioning proportion valve (misnomer.. it's only a switch) will not allow you to bleed the brakes one line at a time. The principle of operation is such that when one line/caliper leaks (or is open for bleeding), hydraulic pressure (M/C-pedal pressure) will cause the valve's internal piston to slide to one side, activating the dash brake light, and closing off the opposite (front or rear) fluid circuit, rendering that closed off circuit un-bleedable. When this happens, the closed off half of the valve will not allow any fluid to be bled through that circuit (front or rear).

===> The trick in this case is to re-center the valve and to bleed one front & one rear caliper simultaneously.

Re-centering a poorly functioning valve can be difficult- I have used DRY compressed air forced backwards through the lines to the valve to force the piston back to its center position (dash light goes off), and I have used simple brake pedal pressure to re-center it. The method used depends on how bad the valve is sticking. You may have to rebuild or replace the valve (switch). The air MUST be dry, or you will be blowing water into the system along with the air.

I have disassembled several of these and documented their internal structure, again for the benefit of forum members.

If you can bleed a C3 brake system without dealing with this problem, then the brake switch is sticking and is not functioning properly… which I find on 9 out of 10 Vette’s.

Bleeding the bakes....

Any method that works for you is fine. Everyone has their preference.
Key essential point: never let the M/C run dry while bleeding. You must re-bench bleed the M/C and start the line bleeding process all over again if the fluid in the M/C drops to, or below the tiny orifices in reservoir.

Gravity
Pedal
Vacuum
Pressurized

Gravity-
You can bleed a -properly functioning- C3 with a small piece of rubber hose and a coffee cup... no special tools.
All you need is a tool to open/close the bleeders.
The rubber hose is attached to the bleeder, the bleeder is opened, fluid is allowed to flow via gravity until clear & bubble free, and the bleeder is then closed. Don’t expect a fire hose… it runs slow. If you’re in a hurry, then this method is not for you.

To avoid rounding off of the bleeder, use a small 6 point socket to initially crack the bleeders open, but use a box wrench to open/close them while bleeding. The wrench can remain on the bleeder while bleeding, a socket cannot due to your bleeder hose connection. Use a box wrench because it has less of a chance of rounding off the bleeder than an open-end wrench. Tubing wrenches are usually too fat to fit here... good for fittings, but not for bleeders.

You can gravity bleed all or one at a time... place the hose on the bleeder and set it up so that the hose is in the bottom of the coffee cup so no air can travel up the hose backwards once there is some fluid in the bottom of the cup. Open a bleeder(s). Let gravity do its thing. Close the bleeder(s).

Most of the time, fluid will not start to flow all by itself. If not, then a few slow pumps of the M/C with the bleeder(s) open should get it flowing. Remember.... the brake switch can foul things up here. Be aware of its principle of operation and take appropriate action if it gives you grief.

Gravity bleeding is essentially the exact same thing as pressure bleeding, except the pressure is much lower.... only induced by gravitational weight of the fluid.

Lisle (and other companies) sells a small plastic cup with hoses & fittings for brake bleeding for around $10. This is one of the cheapest, effective tools you can use.... similar to a hose & coffee cup. I use these exclusively.

This tool is intended for use with the “pedal” method, not on the "gravity" method.
I use it both ways.


Pedal-

Can be done with two people, or one person & check-valve bleeders.

Two person-
Bottom person opens a bleeder, top person presses pedal, bottom person closes bleeder BEFORE top person’s foot reaches the floor, top person lets pedal back up... repeat.
If the bleeder is closed AFTER the top person’s foot reaches the floor, then air can flow back into the caliper. The two people have to set up an agreed sequence of communication for this to work.

Check valve bleeders come in two varieties. One is the replacement bleeder with the check valve built in. The other is the separate check valve in line with a rubber hose, attached to the caliper bleeder.

Either one works if used properly.
You can buy a set of four and bleed all four calipers at once... but I have found this to be "iffy"… results unpredictable. It's better to do one front & one rear together, and then switch to the other pair. With check valve bleeders, you simply attach a hose/cup to the bleeder and open the bleeder(s) and pump the pedal.

Vacuum-

The "Mity-Vac" tool will work if used properly... but not many people can use it properly. It does have one primary flaw.... it sucks air past the bleeder threads and more importantly, past the internal piston o-ring seals instead of sucking fluid from the caliper. You can minimize this by putting pressure on the bleeder threads while drawing fluid, and by going "slow & easy" with the hand pump. Patience is the key here.


Pressure-

The current "DIY" tool for doing this does not seal properly on the C2/C3 M/C. You have to deal with that issue up front. People use all sorts of rigged up solutions (clamps etc) to make this tool work as promised. Professional pressure bleeders do not have this problem... only the $60 DIY version fails the test. This method is by far the fastest, but does not always allow time for trapped bubbles to escape like the slower gravity/pedal bleeding method does, so even after spending the money and using the tool, you may still have to gravity or pedal bleed to get a firm pedal. Brake fluid is thick (viscous) and trapped air bubbles move slowly... they need a little extra time to migrate to the bleeder orifice. Pressure bleeders tend to move the fluid faster, but the bubbles move at their own pace… they hang up on the caliper casting. I’ve seen this with some of the professional grade pressure bleeding systems with clear site glass… you can see the fluid move while a bubble stays in one spot.

If you use DOT5, then keep the pressure very low or you will introduce air bubbles into the fluid which are an issue with both DOT3 and DOT5.... but more so with DOT5.
One final note on pressure bleeders... since they use non-dry air, they can actually force water (from the air) into the fluid, which will eventually cause internal corrosion. Pressure bleeders should be used with dry air only.


Final thoughts-
In all cases, the angle of the calipers can slow down the bleeding process... air bubbles tend to float up.... not down. They look for a high spot. Just sit back and visualize the bleeder design and location and ask: "If I were a bubble, where would I go?"

Adjust your caliper angle as best you can. Calipers do not have to be mounted to be bled. You can place a piece of wood between the pistons of an un-mounted caliper to bleed it. The wood should keep the pistons all the way in their bores... or... if mounted... use jack stands accordingly to change the angle of the car… even a little bit helps. The key to this is knowing how the calipers are drilled internally... you have to take one apart to see the passages.


Fluid-

A lot of myths on the forum regarding fluid.
If you remove ALL water & water laden air from the system, DOT5 will last indefinitely.
If you disassemble a system at a later date and find water (or rust) in a DOT5 system, then either you did not remove all of the water on the first pass, or your rotors are out of spec and are pumping air & water into the calipers.

DOT5 can't be used for cars with ABS because the pulsing forms bubbles, but is fine for C3's. On my own C2, I converted to DOT5 in 1976. 20 years later (1996), I removed all of the fluid, ran it through a strainer to get chunks of rubber out (deteriorated seals) and then re-used it. There was absolutely no rust or water in the system after 20 years. It does not wear out. It does not melt paint like DOT3/4 does. So you can paint your parts and not worry about the fluid ruining all of your hard work.

Some people claim DOT5 is not good for racing because of its lower boiling point and compressibility... others use it for racing with no problems. It depends on the type and intensity of the racing.

For street, DOT5 has no issues.

DOT3 is cheaper, readily available, has a higher boiling point & is less compressible, but it absorbs water and must be changed regularly or your system will rot from the inside out... including the lines if they're not stainless. DOT3 works fine as long as you follow the rules associated with it... specifically, regular flushing.

Converting from one fluid to another:
Either way... disassemble the ENTIRE system and clean it out manually... do not rely on flushing. This includes the proportioning valve/switch. Flushing is at best 50% effective in removing the other fluid and contaminants... especially in the proportioning valve where fluid does not flow "through" the device. Don't waste your time with flushing... it will bite you later on. A manual disassembly and cleaning is mandatory.

This is just some of the info I have gained over the years... since I work on all cars, not just Corvettes.

Hope it helps.

Tom

FeedVaal

And now I do too. Thanks Tom.

DJ Dep

Some side notes....I HAVE seen C3 calipers where there is only ONE brake bleeder screw. So it's not always possible to bleed BOTH halves.

The use of C-Clamps and a wide, flat piece of metal on top of the Motive seal top makes the Motive Brake bleeder 100% leakproof. This is what I've used with NO problems. I will grant that the clamp down chains they provide are pretty crappy. As far as bubbles escaping, I had MUCH better success getting bubbles out with a pressure bleeder than any Mickey Mouse gravity system. And the pressure system forces ALL the bubbles out no matter where they are in the lines. The gravity system may work fine if you are on the planet Jupiter where gravity is a lot more than Earth, but for this planet, pressure is your best way to go.

Dep

Jud Chapin

Great post...Thanks!