Cincinnati Rick

What is the correct method to flush and clean brake lines and master cylinder?


Rick

redoldsman

Probably the best way is to take it to a shop and have it pressure bled. They take the cap off the master cylinder and hook a pump on the top and then open the wheel cylinders and pump brake fluid through the system.

Professur

There are do it yourself pressure bleeders, but it's not all necessary. First off ... are you replacing any lines? Remember that old brake fluid absorbs moisture, and becomes spongy. That reduces the pressure in the lines. Inspect all the hard lines ... particularly under clamps. When you flush it and have new fluid in there .. well you wouldn't be the first person to have a catastrophic failure thanks to that new hard pedal. I speak from experience. I personally recommend changing all the rubber lines regardless. Just like tires over 10 years old aren't a good idea, 10 year old brake hoses aren't any better. Then take a turkey baster and suck almost all the old fluid out of the master cylinder. Refill it with fresh, and proceed with bleeding as usual. You'll know when you've pushed out all the old when the colour changes.

Cincinnati Rick

The lines were replaced by the previous owner when the body was off. I just finished replacing the wheel cylinders, calipers, flex lines to the calipers and 1-damaged brake line. When I opened the MC (which looks to be original), I noticed there was sediment in the bottom of the MC. I'm thinking I should replace the MC. When I was pushing the rubber bladder back into the top of it, I could feel crusty stuff between the rubber and the inside surface. I think it's actually rusted underneath the cap.

Professur

If you're seeing anything in the MC, you need to pull it and at the very least inspect it. Any grit that's gotten that far has likely gotten down further. That's bad juju. Are you comfortable with rebuilding it yourself? Personally, I'd be replacing it.

Cincinnati Rick

I'll probably replace it for now. I'm just trying to get the car on the road again so I can have some fun with it this summer. I'll save the original and rebuild it at a later date when/if I do a total restoration.

Rick

droldsmorland

Look in Jegs or Summit for the $75 pump style brake bleeder from Motive Products. Works like a charm. Because its so easy to use I bleed all of my vehicles at least every two years regardless of mileage. I have a 96 GC Jeep with 227K on the clock with original calipers all 4 sides. Muscle cars that sit get it annually.
As mentioned replace the soft lines for safety.

pogo69

you can open the bleeders with aquarium tubing on the bleeder ends...put the tubing in a coffee can and pump the brake pedal

Octania

Clean off the rubber moisture guard very well, all the crusty deposits.

Remove most of the fluid from the MC

sop out the rest with a lint free rag, and clean out that sediment too

Add fresh juice, bleed until fresh comes out each bleeder.

don71

I too flush the brake system every two years in the olds. The device that Drmorland mentions sounds like the way to go. Especially if you have multiple vehicles.

I've been using a home made fixture that I read about in the car magizines from years ago. If I can find a pic, I'll post it up.

Its a simple plate of steel with a rubber gasket. Threaded on one end to accept an air fitting. This requires a large C clamp to keep the plate on the master. Apply shop air at about 15-20 psi and count to 10 at each corner. Filling the master back up after each bleeder is opened. Takes me about 15 minutes to go around twice using most of a quart of fluid.

This only works on cast iron masters. To use on the modern plastic masters, would take some thinking.

Fun71

Just get a spare cap and attach an air fitting to it. For one of my vehicles that has a round screw on cap, I drilled a hole in a spare cap and attached a 1/4" hose barb with a nut on the inside and a gasket under the barb base. Connect a length of rubber tubing from the air compressor and the barb and voila, a pressure bleeder.

RonFX

Guys:
This is kind of a brake fluid flush question. before the tear down and total restoration of my 66 Cutlass,I installed a new disc brake conversion and used Dot 3 fluid, I did a shake down run to make sure everything worked. I have since installed all new hard lines, T's and misc fittings. The M/C and front hoses are the only thing left that have a trace of Dot 3 fluid. The body has been removed and the new hard lines blown out w/ air and sealed to prevent moisture from getting in the lines. My question is, will it be enough to completely empty out the M/C and spray w/ brake cleaner and then fill w/ Dot 5 fluid it is the only part left w/ a trace of Dot 3 fluid or should it be rebuilt or replaced? I want to use Dot 5 fluid to help protect against moisture destroying all the hard work put into the project
Thanks, Ron

D. Yaros

I went. I looked. I found no unit at $75. Think it now is eighty-five bucks?

My442

You would be better off with a MityVac 7201.


It suctions and dispenses, so you can bleed brakes and fill differentials.


The brake bleeder attachment is extra cost I believe.


Works great.

Fun71

For all of you do-it-yourselfers, here's the link that was the inspiration for my home made pressure bleeder:
http://faculty.ccp.edu/faculty/dreed...atech/bleeder/

Where I diverged was with the pressure tank. Instead of using a hand pump sprayer, I used my shop compressor with the regulator dialed down and a hose barb screwed into the end of the blow gun so the blow gun acts as my on/off valve for air pressure:



Works like a champ and I never have to hand pump a tank, and best of all it cost under $20.

rustyroger

If you want to use silicon based brake fluid you will need to remove all hydraulic moving parts, master cylinder, callipers, wheel cylinders, compensator, and dismantle them to remove all traces of dot3. The fluids are incompatible.
But a good quality fluid should be fine, I let gravity do the work when I change brake fluid. I get the wheels off, put a container to catch the fluid under the bleed nipples, take the top off the master cylinder, open a bleed nipple and lat the fluid come out. I make sure the master cylinder doesn't run too low, when clean fluid comes out I close the bleed screw and move to the next wheel until they are all done.
It takes time, so I have a cup of tea while i go about it.

Roger.