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Old 05-03-2021, 08:55 AM   #1
regan wilson
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C-50 Brakes

What is the process for bleeding brakes on the dual master cylinder setup? Thanks
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Old 05-03-2021, 09:25 AM   #2
CarolinaHD
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Re: C-50 Brakes

What year?
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Old 05-03-2021, 08:17 PM   #3
regan wilson
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Re: C-50 Brakes

1969 350 4-speed Truck. Small cylinder up top with another cylinder and booster behind the drivers side step.
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Old 05-04-2021, 02:01 PM   #4
Bob B.
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Re: C-50 Brakes

When you say dual master cylinder, do you mean there are 2 lines coming out of the firewall mounted master cylinder? If so those systems often have 2 boosters. If there is just one line coming out of the firewall mounted master cylinder and it goes to one booster, that is a single system. That is what most C-50's had. The way to bleed the single system is master cylinder first, then booster, then right rear-left rear-right front-left front wheels. Then master cylinder and booster again. You may have to do this multiple times, you will loose a lot of brake fluid and you have to be careful not to let the master cylinder run dry. It is quicker to use a pressure bleeder if you can get one.

Now for the disclaimers:

Do not mess with medium/heavy truck brakes unless you know what you are doing. Seek professional help if in doubt.

Do not bleed the brakes in an old truck that has been sitting and attempt to drive it unless you pull all the drums and thoroughly inspect the wheel cylinders for leakage. Also inspect all lines, master cylinders and boosters. Check for vacuum leaks and be sure the booster is functional.

Do not attempt to drive the truck unless you are sure of the condition of the brakes. Also make sure the emergency brake is functional. If a single system has a leak it is surprising how quickly the brakes will cease to function.

Don't mean to be offensive, just don't want to see anyone have an accident. Over on one of the Ford forums some clown lost an F-600 down a hill after he messed with the brakes! Luckily he didn't kill himself or someone else.
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Old 05-04-2021, 09:26 PM   #5
regan wilson
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Re: C-50 Brakes

Bob thanks for explanation. It's a single up top. You will in no way be held accountable for you advise. It's probably leaking everywhere.
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Old Today, 05:59 PM   #6
1976gmc20
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Re: C-50 Brakes

That sounds just like the one I had (1965).

I put in an electric trailer brake tee to tow a MH and it was never quite right after that. So I took the tee and controller off and bled the system again and again. It would be fine sitting for any length of time or going downhill but it would somehow bleed off when going uphill under a load. If I had to stop going uphill, I learned to pump up the brakes before putting in the clutch. Funny, it never lost fluid either

To add insult to injury, the brakes on our old MH never worked either - so it was a waste to break into the system for the controller. I should have just hooked up the wires and used it by hand though it wouldn't have done any good anyway.
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