VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Bleeding brakes

Trying to bleed brakes and I came across this

Another angle
All wheels had a standard bleed fitting, but this wheel had this. How do I bleed with this thing?
Thanks
Mike A

Remove the little bolt in the center and bleed by lossening the valve.
The little bolt is only a plug in the bleeder valve opening. 1936-1950 wheel cylinders made by Delco had this feature. You could also remove and discard the bolt and leave it out or install a new bleeder and discard both that and the original bleeder.

Chevgene,
Thank you for info, I was hoping it was that easy.
-I bled 3 of four wheels and need to pump brake to get pressure.
-i hope the last wheel is the culprit.
Mike A

I.Help! Tried bleeding brakes using the one man little bottle and check valve system from harbor freight following what I thought to be the correct process, but pedal goes to the floor until I pump it a few times.
1. Started from driver rear, next driver front, next passenger rear and finally passenger front.
2. Is it possible my new master cylinder is defective?
3. When I pump pedal I can see fluid moving in my master cylinder reservoir(hopefully normal)
II. Is this the only proper way to bleed below?
1a. I watched a video showing two people(one pumping 5 times, holding down o 5th.
2a. 2nd person opens bleed valve until steady stream of fluid escapes then closes.
3a. This process is repeated at each wheel.
I am getting depressed, I want to drive my 38.
Thank you,
Mike A

Mike -

I was always taught to bleed - 1-left rear, 2-right rear, 3-right front, and finally 4-left front. You might try that next and see if it helps. Sounds like you still have air in system. Are brakes adjusted up properly??

Jim.

Jim,
I went by the chevy manual
http://chevy.oldcarmanualproject.com/shop/1938/38csm115.html
My biggest concern is the master cylinder is defective.
Your suggestion makes sense and that is what I thought until I read the manual.
Thank you for the advice. I think i will try the two person method.
Mike A

Check all fittings to see if any brake fluid is leaking, including the brake light switch.

If you pump the pedal slowly several times, and it builds up pressure, but still feels soft, then air is the big culprit...took me 4 tries to get most of the air out.

While looking in my MC fill hole with a flashlight, I pumped the brake with my hand, and the only time I saw fluid move was when I released the brake, and the fluid shook for a split second.

In the end, I have found that vacuum pump bleeding worked better with silicone fluid, as the fluid is less disturbed at the MC. I used a Lisle vacuum pump, similar to the HF pump.

I'm at 3rd attempt. Thank you for the advice, it all helps.
Mike A

I have never had good results with vacuum pump bleeding methods on older systems you will pull air into the system in older systems. The best way is to use two people. Keep the reservoir full and one person pumping on command and one opening and closeing the bleeder valve. I have never used the pressure pot on top of the master cylinder like was used by many Chevrolet shops.

Hello everybody,

1st: The rule is to begin at the wheel most far away from the main cylinder...rear right as written before.

2nd: Because I have no man to help me I use a system called "Easybleed" sold here in Germany.
It uses the air pressure of a tire.
There is a bottle you fill with brake fluid, and it is to be connected with an self made adapter to be replaced with the main cylinder filler cap during the bleeding proceed.
Of course there were a lot of usual caps for most modern cars coming together with the kit when I bought it but I asked a friend from here to bring me an original 1940 cap to adapt it for that system when he came to visit me in last may.

Everything installed the pressure of the tire will allow me just to crawl from wheel to wheel opening the bleeder screws and service everything alone without need of any helpmate.

Because there is involved a bottle filled with brake fluid the main cylinder will never run ot of fresh fluid and I can do the whole bleeding proceed within few minutes alone.

To feed the system by pumping the brake pedal includes a risk always. If you press the pedal very deep and you reach zones you will never touch during normal driving there might be some corrosion inside the main cylinder and the rubber rings at the piston might get a damage when touching usually untouched maybe rusty zones inside the cylinder.

So I am very happy with my airbleed system...

Stefangermany

that is the same "pressure " method used at Chevrolet shops for years.

I've never encounterd much trouble bleeding brakes and I don't always follow the longest line first...I'll do it all "willy-nelly" and everything comes out fine...Inch travel on the pedal and rock hard...But, everything's new and bench bled first...A little adjustment needed...New fittings, a clear tube and a jar with some fluid...I could be wrong, but I have a theory that eventually trapped air will rise to the master...Law of physics...But, old car masters are pretty low...

Newer cars with all disc brakes are a piece 'o cake...No bleeding...I start with a bench bled master, then do the rotor pads and push back towards the master...Usually no overflow at the master...Jaguar's are super simple...All that's needed is a screw driver in the rear and a large torques in the front...Done in a New York minute...The '47 takes 10 times longer...Stinking drum brakes...But, you get the hang of it...And probably only have to do it once...Then there's the parking brake cable...Does the fun ever end...?

I have had quicker success with the pressurized fluid container as the fluid isnt "shaken" during the pressurizing process.
With most british cars "pumping" the fluid in from the wheel cylinders and extracting the fluid from the master cylinder can does work.
The vacuum at wheel cylinder can give false indication as air can be drawn in around the bleed screw threads.
Tony

Where can i find one of these or what haste others used to replicate?


Still have air in my lines, but can't seem to keep master cylinder full while bleeding with help. What a pain in the neck.
Thanks
Mike A

If, for whatever reason, you are unable to keep fluid in the master cylinder, you will not eliminate air in the brake system.

The 38 master cylinder is small and access is a whole a little larger than a golf ball under driver floorboard. The picture I posted is a GM tool used to monitor master cylinder fluid level While bleeding brakes. The adaptor neck connects to the master cylinder filler whole while the clear bottle allows you to see fluid level.
-someone sits in car and holds brake pedal down while bleeding, but also has to monitor fluid level.
Not fun

Understood.

This is what I use to bleed the brakes on my stuff. I have even used it on my '53 2 ton with a hydrovac and it worked perfect.

http://www.motiveproducts.com/

I saw this bleeder highlighted on one of the car shows, Gearz or Motorhead Garage or such. Product seemed to be the answer for a "one guy operation".

Fill master cylinder and crack one bleeder screw open at a time and let it drip until you see no bubbles,I use the gravity bleeding method when I have no one to help me which is 99 percent of the time. When I replace a part I will fill it with brake fluid before installing and then crack the bleeder to get the rest of the air out and need no help most of the time.

We use a pressure brake bleeder in the shop. Keeps master cylinder full and pressurizes system. On e man goes around and opens each bleeder one at a time. I can do my 6X6 in ten minutes. It is also very handy to check for leaks as the system is under pressure. They range from simple $30.00 units to $500.00 commercial units like we use. It's the only way to fly.

I use the vacuum sucker and if used properly it works great.

you build up the vacuum first and then whatch the flid run through the clear plastic tube. When no bubbles can be seen your done.
Be sure to follow the bleeding sequence in the shop manual for your year and model car.

When the bleeder nipple has provision for a hose I keep open end under fluid and allow to gravity bleed, when no bubbles appear give the pedal a couple of quick pumps and close that bleeder. Then move to next bleeder.
Tony

Mike: I had thought about doing something along the lines of this (with 1,021 projects going on at the same time, haven't tried it yet):

Take the MC nut cover off, see if I can find an equivalent PVC cap/brass nut cap/plastic, etc.
Drill hole in the middle of that equivalent cap, tap with 1/4"NPT, put a brass 1/4" barb in there, screw it in the MC.
Get a canister like the hard plastic 20oz cup that comes with a HVLP spray gun, add a barbed fitting to the bottom.
Secure the cup vertically somewhere near the MC, at about 12" above the highest brake line, and attach clear tubing on the barbed ends.

20oz should be plenty, and you can watch it from all 4 sides.

If you are using silicone DOT-5 like I am, it will take awhile for the bubbles to migrate upwards. Might have to heat up the fluid to speed up that process.

In this weather, probably will take a week or two per wheel for the bubbles to migrate.....

Wonder if anyone has used speed bleeders? Very popular in the motorcycle community, I thought of trying them out on my next car's scheduled brake work.