Changing brake fluid

[Stinson]

Hello,
I have just installed a new brake system on my car with SS lines, shoes, springs, and etc. Must I put the hubs on prior to bleeding the lines with new DOT 3?
Many thanks,
Ty Stinson 

[35-709]

Absolutely!  Sometimes, with some vehicles, it is possible to gravity bleed (if you have the time) and the drums are not needed, but otherwise if you do not put the drums on you are almost certain to blow the ends out of the brake cylinders with fluid pressure.
Geoff N.

[TJ Hopland]

Yep if you put any pressure in the system without the drums to hold things together you will at the very least be cleaning up a mess of fluid and putting the piston back in the cylinder.  If you did not have the shoes in you will be cleaning up a big mess and looking for the piston(s) because it shot out.

On a big project I use a tool like this to get things started but then do the final the old way with the wife or kids pushing on the pedal.


$20 from harbor freight
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92474

Many other auto related uses for the tool also, at that price no reason not to have one in the tool box.  Many parts stores now have 'import' tools also that work just fine for the back yard mechanic.

[Stinson]

Thank you, thank you to Geoff and Hopland.

Dumb question: How does that tool work to start things. Does it press fluid through a brake cylinder to the master cylinder (with or without the filler cap off) and then through to another wheel cylinder at the far end with a bleeder open, and then require normal bleeding procedures by pumping fluid from the master cylinder to each of the other brake cylinders?
Thank you,
Ty Stinson

[TJ Hopland]

The dumb part is not to ask the question if you dont know the answer.

That tool is a vacuum pump and gauge (also handy for working on other parts of the car).
You plumb that canister inline between the pump and the open bleeder screw on the caliper or wheel cylinder.  You then operate the pump.  This applies vacuum to the open bleeder screw and should then suck air and hopefully eventually fluid from the MC.  When the fluid reaches the canister it collects there rather than getting sucked into the pump.  The problem I have with these types of tools that suck on the bleeder screws or the hose/ check vavle in the fluid method is the bleeder screw is not designed to seal around the threads so with the check valve or hose in the fluid method you could suck air past the threads of the open bleeder screw and you are right back where you started with air in the system.   At least with the vac tools you are not releasing the pedal and sucking air/ fluid back so its less of a problem.   With a fresh system like you have it will take forever pumping the pedal to get fluid into the lines.  Thats where I use the vac tool to get things flowing then I finish off with the good old reliable 2 person method.  Getting things close by gravity or a vac tool helps this process because the pedal pusher only has to push the pedal say 10 times rather than say 100. I find that the wife or kids are only good for about 10 presses before the complaints start coming, your results may vary.  Dont forget to keep the reservoir full or you will be starting all over again.

The gravity method is simple.   Fill the reservoir leave the cover off.  Go open one (or all) of the bleed screws.  The pressure of the fluid (assuming the MC is higher than the bleed screws) will push the fluid through the system.  Keep the res topped off.  When you start to get fluid out the bleeds close em up and then get your assistant to finish them off. This method works well with between 12-24 ounces of your favorite beverage.  A good show (or 2) on your shop tv or several good tunes on the radio also helps.  A nice comfy chair is mandatory. 

I have a tool that mounts to the top of the MC and then forces fluid into the system.   It was expensive and messy and did not solve the problem I had with the car I bought it for.  I had air trapped in the system in a place I was not looking or bleeding from so it did not help.  Its been collecting dust on my shelf for 3 years now and I have done several brake jobs since then.  I tried to use it on by boat trailer but could not get it to seal on the MC.  Ended up getting the wife to lean on a piece of pipe hooked to the coupler and it worked fine. 

[Ty]

Thank you Mr. Hopland.
I had some special wheels made and had to send a front and rear hub for various drilling measurements. So, I only have two of them sanded, cleaned, primed and painted at this time. Tomorrow morning I would like to put them on so I can install two of the original wheels and tires and use the gravity system to fill the new lines (but will not pump the brake pedal) so that when the other two hubs arrive I can quickly finish with the standard method of pumping the individual units until the fluid runs free of air.
Is there a problem with this idea?
Many thanks,
Ty Stinson
CLC22330

[TJ Hopland]

Sounds like a good plan to me.

[Ty]

Well, as it turns out, the front block is higher than the master cylinder. So, I must wait for my two hubs to return. I finished the brake system other than adding the fluid, two hubs now look like new front and back, primed, painted Masters black, the wheel bearings are all cleaned and repacked, all four wheels have been sand blasted, primed, painted, and tires mounted, balanced, and as of 7:30 pm today two of the tires are now mounted on the car. July 4th will be 5 years the car has been in my garage but may soon role out under its own power.
Ty Stinson