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Username Post: Brake question        (Topic#341418)
jbouchard 
Contributor
Posts: 307

Reg: 08-07-12
12-22-16 08:54 PM - Post#2667386    

Hello.

Recently I redid all the brake lines on my 41, in addition to rebuilding all the wheel cylinders and the master cylinder. There were a few minor drips at some of the fittings where I did not replace the original brass fittings, but other than that I did not see any other leaks.

I went in it the other day, however, to move it, and all the fluid was out of the master cylinder. I was just going to fill it back up and run it locally spongy, but any ideas on fluid loss and making sure the system has integrity?

Thanks,

Judson



 
J REID 
Member
Posts: 684

Loc: SW Minnesota
Reg: 04-09-04
12-27-16 09:30 AM - Post#2668037    
    In response to jbouchard

If there are leaks at all it will leak down in time. The brake system has to be leak free. I would suggest finding all leaks, tightening the fittings if possible, replacing if not.
A late Merry Christmas

57 210 4dr, 57 2dr ht project, 67 Chevelle SS project, 40 Chev coup project


 
jbouchard 
Contributor
Posts: 307

Reg: 08-07-12
12-30-16 06:43 PM - Post#2668585    
    In response to J REID

Thank you very much. Judson



 
Ray P W 
Contributor
Posts: 322

Reg: 09-30-15
12-31-16 06:19 PM - Post#2668755    
    In response to jbouchard

Judson,

In owning my '36 Chevy pickup for over 50 years I've never had to replace any of the fittings but I do replace the soft copper washers at the wheel cylinders whenever the wheel cylinder fitting bolts and/or flex hoses have to be loosened for any reason. Is that where your leaks are?

Ray W



 
jbouchard 
Contributor
Posts: 307

Reg: 08-07-12
01-09-17 11:21 AM - Post#2670278    
    In response to Ray P W

Hi Ray,

The leaks I observed were at the junction of some of the brake lines and the copper Tee's. The old lines were rusted out, so I cut and flared new brake line. I have heard that sometimes the copper fittings already have wear from the old brake lines since copper is a soft metal. But, to be honest, I have not looked at it in the past few weeks. I need to get it up on jacks and take a good look at it again.


Judson



 
Ray P W 
Contributor
Posts: 322

Reg: 09-30-15
01-09-17 01:41 PM - Post#2670297    
    In response to jbouchard

Hello Judson,

The first few double flares I made in brake tubing didn't turn out too well. When I tightened the flare nuts the poorly formed flares dented the inverted flare part of the softer brass fitting causing problems. With practice I can now do better. A perfectly formed flare in the tubing does not dent the fitting sealing surface. This hobby gives us an opportunity to learn those kinds of skills and, to me, that's part of the fun.

If you look at the fittings with a magnifying glass you'll be able to see the condition of the fittings. If they are dented I don't think it's possible to get a leak free joint.

Ray W



 
jbouchard 
Contributor
Posts: 307

Reg: 08-07-12
01-11-17 08:57 AM - Post#2670565    
    In response to Ray P W

Hi Ray,

I agree with you. It is fun learning the skills to maintain the older cars. They have a simplicity, yet skill, I appreciate.

FYI-I did get a look at the brakes on the Chev today. I filled the reservoir with fluid and tried to build up pressure by pumping the pedal-but no pressure built up. I looked again at the reservoir and the fluid level was unchanged, so I am assuming I need to pull my master cylinder. Im guessing fluid is blowing past the rubber seal.

Take care,

Judson



 
Ray P W 
Contributor
Posts: 322

Reg: 09-30-15
01-11-17 09:52 AM - Post#2670570    
    In response to jbouchard

"I filled the reservoir with fluid and tried to build up pressure by pumping the pedal-but no pressure built up. I looked again at the reservoir and the fluid level was unchanged, so I am assuming I need to pull my master cylinder. Im guessing fluid is blowing past the rubber seal."

Good morning Judson.

If your system has a lot of air in it at first it feels like no pressure. Still, if you bleed it and let out that air, the volume of air will decrease with what my wife and I call our "brake up-downs" and you will feel some increasing pressure and finally you'll get a lot of bubbles and some fluid. Continuing the process, the volume of fluid will increase and the bubbles will decrease.

This only works if the bleeder valve is closed BEFORE the pedal is allowed to rise. Otherwise the same air that was just expelled is drawn back in and nothing is accomplished.

You can do it!

Ray W



 
jbouchard 
Contributor
Posts: 307

Reg: 08-07-12
01-11-17 06:53 PM - Post#2670649    
    In response to Ray P W

Thank you, Ray. I guess I kind of missed the obvious...that's why I am very appreciative of the forum on Chevytalk. Thank you. Judson



 
Ray P W 
Contributor
Posts: 322

Reg: 09-30-15
01-12-17 03:47 PM - Post#2670794    
    In response to jbouchard

"Thank you, Ray. I guess I kind of missed the obvious"

You're very welcome Judson. There isn't a person alive who has tried new things who hasn't also "missed the obvious" during the learning process. Bleeding brakes requires coordination between the person pressing and releasing the pedal and the person opening and closing the bleeder screw.

One more thing I would suggest is bleeding through a clear vinyl tube with its end submerged in brake fluid in a clear container. That way you will see the bubbles and liquid discharging from the wheel cylinders and know when all the air is expelled. Don't forget to keep adding fluid to the MC as you bleed the system!

If you are using DOT5 (Silicone) brake fluid I've found that it is necessary to wait a couple of days between filling the MC and bleeding the system. That is probably because DOT5 forms what I call "microbubbles" when it is poured from the container into the MC and it takes a couple of days for those microbubbles to coalesce into visible bubbles that can be bled out.

Some "experts" claim that DOT5 is compressible yielding a "soft" pedal. They must have been sleeping through high school and college physics where we learned that liquids are not compressible. Or they did not get as far as high school, also a possibility.

Ray W



 
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