The Ford Barn

CA Victoria · 06-12-2011, 11:27 PM

I have a 35 with 39 front/46 rear brakes, I bought the ford non-op so I don't know if the brakes ever worked. I have replaced my older MC with a new 67 Ford unit. Put kits in the cylinders. I Blead the MC properly and used a power bleeder. First 1/3 of pedal travel is soft and it firms up 1/2 way down. Stops the 35 but not as well as it should. I can place shunts on the front flex lines above the wheel cylinder and I have a solid pedal. When I take the shunts off I have a soft pedal. The front flex lines are older but do not apear to be in bad condition. The free play has been taken up in the pedal travel. The cylinders don't apear to be leaking.....next step is to buy new wheel cylinders or to buy the Chevy C-20 MC suggested in an earlier post?
I have read previous posts regarding the larger wheel cylinders and the MC not able to fill the fronts enough to get enough brake.
Have I overlook something?
Suggestions?

r797w45 · 06-13-2011, 07:22 AM

Check adjustment on front brakes ?? Hard to get right at bottom anchors.

Steve.

Steve.

DICK SPADARO · 06-13-2011, 09:33 AM

Please list all parts of the system your vehicle uses, like what brakes, pedal assembly, master cylinder used. From your post it is assumed that you are using stock Ford 39-48 brakes, late model master cylinder, an unknown pedal assembly and have adjusted the brakes correctly to start.

This is a relatively simple system based upon fluid displacement. If you are using old Ford style brakes start to trouble shoot by making sure that you have the brakes correctly adjusted. Then have purchased a replacement master cylinder approximately the same size bore as the one used for the wheel cylinders, example if you have early Ford wheel cylinders the original master cylinder was 1 1/16" bore so you need a replacement master cylinder around 1 to 1 1/16" size. Also note that you should check to see that the replacement master cylinder is a drum/drum not a disc/drum unit. If you chose one smaller (7/8") you will not displace enough fluid to fill the 4 wheel cylinders and the brakes will work but be soft and exhibited by long pedal travel. If you chose a larger bore master cylinder (1 1/8"+) you will displace an adequate supply of fluid with a shorter pedal travel but the pressure applied to the system will decrease, and you will have to push harder on the pedal. This can also be compounded if you have a homemade pedal assembly with the incorrect pedal to pushrod arm ratio.

First assumption is that you have too small a master cylinder, and this is based upon your statement that if you pinch off the flex lines the rear brakes work fine. This would indicate that the master cylinder displacement is too small, you need to check the size of your master cylinder bore.

alanwoodieman · 06-13-2011, 11:00 AM

check the pedal rod to master cylinder play, I suspect that there is too much free play in this rod, it is suppossed to be adjustable. from under the car reach up and see if you can move this rod, not the pedal, just the rod, if it is loose pull the pedal down until there is no more free play, if you move it much you are out of pedal travel before you are out of master cylinder travel, too tight and the master cylinder will not let the fluid back in. should have just a little play--let us know what you find!

CA Victoria · 06-13-2011, 09:12 PM

Dick and Alan, Thank you for your insight.
To add a little info, the pedal assm. is a 39 in a 35 PU. The MC push rod has minimal (1/16" or less) end play until it moves the plunger. Checking, the MC I installed, and it has a 1" bore and is for drum/drum brakes. I'm going to replace the brake flex lines tomorrow to eliminate any concerns that they may fouled up inside. Could I benifit from the volume of a 1 1/8" MC? What size bore did the 39 MC have?
Thank you, Tim

CA Victoria · 06-16-2011, 03:00 PM

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I purchased new brake lines. The previoius owner did not install the copper gaskets inbetween the brake line and the wheel cylinders. There wasn't a detectable leak; what fluid I noted I asumed was from the bleeding sequence. Good brakes now.
Thank you to all who responded, and to the Master Mind who concieved this web forum.
I've learned a ton of stuff.

06-12-2011, 11:27 PM	#1
CA Victoria Senior Member Join Date: Feb 2011 Posts: 2,123	39 Brake Problem I have a 35 with 39 front/46 rear brakes, I bought the ford non-op so I don't know if the brakes ever worked. I have replaced my older MC with a new 67 Ford unit. Put kits in the cylinders. I Blead the MC properly and used a power bleeder. First 1/3 of pedal travel is soft and it firms up 1/2 way down. Stops the 35 but not as well as it should. I can place shunts on the front flex lines above the wheel cylinder and I have a solid pedal. When I take the shunts off I have a soft pedal. The front flex lines are older but do not apear to be in bad condition. The free play has been taken up in the pedal travel. The cylinders don't apear to be leaking.....next step is to buy new wheel cylinders or to buy the Chevy C-20 MC suggested in an earlier post? I have read previous posts regarding the larger wheel cylinders and the MC not able to fill the fronts enough to get enough brake. Have I overlook something? Suggestions? Last edited by CA Victoria; 06-12-2011 at 11:28 PM. Reason: spelling!

06-13-2011, 07:22 AM	#2
r797w45 Junior Member Join Date: May 2010 Location: Austalia Posts: 4	Re: 39 Brake Problem Check adjustment on front brakes ?? Hard to get right at bottom anchors. Steve. Steve.

06-13-2011, 09:33 AM	#3
DICK SPADARO Senior Member Join Date: May 2010 Location: Altamont, NY Posts: 1,004	Re: 39 Brake Problem Please list all parts of the system your vehicle uses, like what brakes, pedal assembly, master cylinder used. From your post it is assumed that you are using stock Ford 39-48 brakes, late model master cylinder, an unknown pedal assembly and have adjusted the brakes correctly to start. This is a relatively simple system based upon fluid displacement. If you are using old Ford style brakes start to trouble shoot by making sure that you have the brakes correctly adjusted. Then have purchased a replacement master cylinder approximately the same size bore as the one used for the wheel cylinders, example if you have early Ford wheel cylinders the original master cylinder was 1 1/16" bore so you need a replacement master cylinder around 1 to 1 1/16" size. Also note that you should check to see that the replacement master cylinder is a drum/drum not a disc/drum unit. If you chose one smaller (7/8") you will not displace enough fluid to fill the 4 wheel cylinders and the brakes will work but be soft and exhibited by long pedal travel. If you chose a larger bore master cylinder (1 1/8"+) you will displace an adequate supply of fluid with a shorter pedal travel but the pressure applied to the system will decrease, and you will have to push harder on the pedal. This can also be compounded if you have a homemade pedal assembly with the incorrect pedal to pushrod arm ratio. First assumption is that you have too small a master cylinder, and this is based upon your statement that if you pinch off the flex lines the rear brakes work fine. This would indicate that the master cylinder displacement is too small, you need to check the size of your master cylinder bore. __________________ dickspadaro.com

06-13-2011, 11:00 AM	#4
alanwoodieman Senior Member Join Date: May 2010 Location: upstate SC Posts: 2,984	Re: 39 Brake Problem check the pedal rod to master cylinder play, I suspect that there is too much free play in this rod, it is suppossed to be adjustable. from under the car reach up and see if you can move this rod, not the pedal, just the rod, if it is loose pull the pedal down until there is no more free play, if you move it much you are out of pedal travel before you are out of master cylinder travel, too tight and the master cylinder will not let the fluid back in. should have just a little play--let us know what you find!

06-13-2011, 09:12 PM	#5
CA Victoria Senior Member Join Date: Feb 2011 Posts: 2,123	Re: 39 Brake Problem Dick and Alan, Thank you for your insight. To add a little info, the pedal assm. is a 39 in a 35 PU. The MC push rod has minimal (1/16" or less) end play until it moves the plunger. Checking, the MC I installed, and it has a 1" bore and is for drum/drum brakes. I'm going to replace the brake flex lines tomorrow to eliminate any concerns that they may fouled up inside. Could I benifit from the volume of a 1 1/8" MC? What size bore did the 39 MC have? Thank you, Tim Last edited by CA Victoria; 06-13-2011 at 09:12 PM. Reason: spelling

06-16-2011, 03:00 PM	#6
CA Victoria Senior Member Join Date: Feb 2011 Posts: 2,123	Re: 39 Brake Problem Solved Sponsored Links (Register now to hide all advertisements) I purchased new brake lines. The previoius owner did not install the copper gaskets inbetween the brake line and the wheel cylinders. There wasn't a detectable leak; what fluid I noted I asumed was from the bleeding sequence. Good brakes now. *Thank you to all who responded, and to the Master Mind who concieved this web forum.* *I've learned a ton of stuff.*