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1938 Buick Century Brake issues


1938buickbob
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I am pulling my hair out trying to bleed the brake lines on a 1938 Buick Century!  I bought it last fall from someone who said it needed a new master cylinder. He gave me the newly rebuilt master cylinder that he never got around to install. I filled it with fluid, got the air out of it. It seemed to work just fine in the vice. It shot a stream of fluid into a can  when I activated the push rod. I installed it and started the bleeding process. I can't get a drop of fluid to come out any of the bleeder valves when a pumping the brake pedal. I even bought a vacuum pump to apply some pressure. Yes, the master cylinder is full. When using the vacuum pump do I need to still pump the brake pedal? Should I leave the cap off the master cylinder. I even bought these bleeder stems that all the fluid and air to escape but not suck back in, still nothing! I've bled brakes before but never had this problem. Could I have bad brake lines? How do I know?20220504_220701.jpg.3a9efc0f79ccf9d3c8bc12cb6a7665f5.jpg

Edited by 1938buickbob (see edit history)
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There has to be a restriction in the lines. You can check by disconnecting the MC and using your vacuum pump to create suction at one of the bleeder screws.  If you can suck air, there is no obstruction. If you can't, that is your problem.

 

Beautiful Buick, by the way. One of my favorites.

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Did you replace the rubber hose behind the master cylinder? If not, I would first try replacing that. It is the most likely source of your obstruction.

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8 hours ago, 5219 said:

There has to be a restriction in the lines. You can check by disconnecting the MC and using your vacuum pump to create suction at one of the bleeder screws.  If you can suck air, there is no obstruction. If you can't, that is your problem.

 

Beautiful Buick, by the way. One of my favorites.

That all makes sense. I will try that. I think I did disconnect the master cylinder at one point and tried creating suction pressure but one of my new bleeder valves had a defect (the needle valve that prevents air from being sucked in was malfunctioning and stuck)and might have misled me. I'm almost to the point of replacing all the brake lines, but I need to verify for sure that there is an obstruction 

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2 hours ago, MCHinson said:

Did you replace the rubber hose behind the master cylinder? If not, I would first try replacing that. It is the most likely source of your obstruction.

No, I did not replace anything but I will look into it. Thanks

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1 hour ago, DonMicheletti said:

Is the rod between the pedal and the cylinder adjusted correctly? If not, the master cylinder piston may not be traveling back enough to clear the reservoir port.

 

Not sure about any adjustment. The only thing I did was mount the master cylinder.  I had to adjust one end of the master cylinder where the the pin locks into a bar from that moves forward when you press the brake pedal. In order to get the pin to line up you have turn an adjusting nut on the rod at one end of the master cylinder. That's all I did.

20220505_125615.jpg

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41 minutes ago, DonMicheletti said:

Another question.  Did the brakes work before you replaced the master cylinder? If they did, something is wrong with the new installation not anyting else.

I bought the car without a master cylinder.  He handed me the rebuilt part but it was not in the car. So to answer your question, no, the brakes were not working. He told me he drove it to a car show 2 years ago. Obviously,  he must have experienced brake problems.  Maybe, the other master cylinder was bad and maybe there are more issues. I looked at the brakes in the front - everything looks good. Wheel cylinder not leaking and brakes are probably 80% good

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3 hours ago, pont35cpe said:

84yr old car, if all original brake lines, they are most likely rusted inside, restricting fluid flow. You may have to replace all the brake lines. This was the problem with my 86yr old`36 Buick.

Probably are original,  but I'm not 100% sure. Look old...lol

What kind of brake lines did you install.  Stainless steel, copper, pvi? Amazon, ebay?

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 I did mine about 6yr ago with a universal metal line kit, of various lengths, with fittings, that i bought on ebay. Here is one that is listed now,  https://www.ebay.com/itm/303737421613   If you are a do it yourselfer, routing/bending/anchoring. The kit i listed, says the lengths of tubing are labeled as to where they go, so may not be too difficult.  Be sure to verify size(Dia.) of tubing is same as your original lines, OD of my `36 lines are 1/4". I don`t know of anyone, but there maybe some brake line specialists, that sells a pre-bent tubing kit to fit.  Good luck.

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In adjusting that brake rod, there should be a tiny bit of freeplay before you begin to feel resistance from the master cylinder piston.

The fact that you get nothing is suspicious. I'd be surprised if all the brake lines are plugged.

Have you tried to preeurize the master cylinder with compressed air to see if you can force fluid through the lines ?

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Flex hoses can deteriorate over the years and the lining come loose, blocking the hose. If the flex hoses are at all cracked or old it is best to replace them as part of a brake job. As far as the metal lines go I am a fan of the new cunifer lines, a little more expensive but easy to work with and will not rust or corrode like steel.

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Late to the conversation but I did a complete brake job about 3000 miles ago (51 Super) and recently started the car and pedal went to the floor. I had no leaks. I put in a Delco rebuild kit and did a thorough vacuum bleeding and all is well, the only thing I could come up with is the check valve in the master cylinder failed. 

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On 5/5/2022 at 3:40 PM, pont35cpe said:

 I did mine about 6yr ago with a universal metal line kit, of various lengths, with fittings, that i bought on ebay. Here is one that is listed now,  https://www.ebay.com/itm/303737421613   If you are a do it yourselfer, routing/bending/anchoring. The kit i listed, says the lengths of tubing are labeled as to where they go, so may not be too difficult.  Be sure to verify size(Dia.) of tubing is same as your original lines, OD of my `36 lines are 1/4". I don`t know of anyone, but there maybe some brake line specialists, that sells a pre-bent tubing kit to fit.  Good luck.

I appreciate the information and advice. I'm out of town for a few days and hope to get back at this as soon as I get back.

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On 5/5/2022 at 6:04 PM, DonMicheletti said:

In adjusting that brake rod, there should be a tiny bit of freeplay before you begin to feel resistance from the master cylinder piston.

The fact that you get nothing is suspicious. I'd be surprised if all the brake lines are plugged.

Have you tried to preeurize the master cylinder with compressed air to see if you can force fluid through the lines ?

I'm gone out of town but the last time I messed with it I got no resistance.  The 1st thing I plan to do when I get back is disconnect the the line leaving the master cylinder and see if I can pull a vacuum through the open line. I guess if it holds pressure than the lines are blocked. I'll let you know what happens.  Thx for the advice

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On 5/7/2022 at 10:27 AM, Dennis Hagen said:

Late to the conversation but I did a complete brake job about 3000 miles ago (51 Super) and recently started the car and pedal went to the floor. I had no leaks. I put in a Delco rebuild kit and did a thorough vacuum bleeding and all is well, the only thing I could come up with is the check valve in the master cylinder failed. 

The master cylinder i have installed was provided by the previous owner who bought it rebuilt but never installed it. I'm taking for granted that the rebuilt master cylinder was rebuilt correctly. I did the bench bleed and it seemed to be good. I'm concerned about the condition of the brake lines. They look like original; if so, need to be replaced anyways... were talking 84 yrs...

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On 5/5/2022 at 6:55 PM, Rusty_OToole said:

Flex hoses can deteriorate over the years and the lining come loose, blocking the hose. If the flex hoses are at all cracked or old it is best to replace them as part of a brake job. As far as the metal lines go I am a fan of the new cunifer lines, a little more expensive but easy to work with and will not rust or corrode like steel.

Where did you buy your cunifer lines? EBAY?

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