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#1 |
Registered User
Join Date: Apr 2018
Location: Highbridge
Posts: 38
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68 c10 brake problems
Hi all. Ive got 68 c10 with s10 front discs and camaro rear axle with druns. I got in the truck this week and the brake pedal went to the floor. It was fine when i parked it up last time. Fluid level is good. It had dual master cylinder with a remote booster for the front brakes. Ive changed the master cylinder and no change. If i pump the pedal a few times a get a good pedal but leave it 3 seconds and then press it and goes to the floor again..i pumped them 40 times and the fluid level didnt drop and no visable leaks anywere. Could this be air in the system if the old master cylinder failed or any other ideas? The strange thing is dual system master cylinder i thought i would only loose front or rear not both. The brakes do work just right on the floor..
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#2 |
Registered User
Join Date: Jun 2015
Location: @
Posts: 890
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Re: 68 c10 brake problems
sounds like air in the system
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#3 |
Registered User
Join Date: Apr 2018
Location: Highbridge
Posts: 38
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Re: 68 c10 brake problems
Last edited by Gav2606; 08-05-2018 at 04:03 AM. |
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#4 |
Registered User
Join Date: Apr 2018
Location: Highbridge
Posts: 38
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Re: 68 c10 brake problems
The block that the pipes go into. Is that a propertning valve. There is one hole with a bolt in it and its totally dry with no fluid coming out..is that correct? Also is the wire on the bottom for the brake warning light?
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#5 |
Registered User
Join Date: Jun 2018
Location: Fuquay-Varina, NC (Just outside of Raleigh)
Posts: 237
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Re: 68 c10 brake problems
That is the proportioning valve, the wire is for the break warning light, I have no idea if the "dry hole" is correct.
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#6 |
Registered User
Join Date: Oct 2016
Location: Dallas Texas
Posts: 3,095
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Re: 68 c10 brake problems
Wow, I've never even seen a remote booster before.
The pumping action you describe indicates a failing MC plunger. What if you pump up the brake pedal and keep the pressure on it. Does it slowly find its way to the floor while you hold the pressure on the pedal? Air in the lines would make for a spongy, mushy pedal because that air will compress where hydraulic fluid without any air will not. -klb
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67 C10 fleet fuel injected '70 402, 700r4, 3.73 posi 07 335 sport turbo 6sp 94 Trans Am GT LT1 6sp posi -- sold after 22yrs 99 540 sport V8 6sp -- sold 73 240z L24 4sp -- given to friend 68 C10 step 350/350 3.73 open -- sold |
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#7 |
Who Changed This?
![]() Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,459
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Re: 68 c10 brake problems
If you already replaced the master cylinder, the culprit is likely to be the slave cylinder in the booster is bypassing. I've never seen a setup like that before, BTW.
If it were mine, I'd be installing a conventional setup using the booster between the interior pushrod and the master cylinder. No offense, but that looks Mickey Mouse to me.
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA Last edited by Steeveedee; 08-05-2018 at 12:54 PM. |
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#8 |
Registered User
Join Date: Apr 2018
Location: Highbridge
Posts: 38
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Re: 68 c10 brake problems
Yeh i am thinking i should change it all to a more modern set up. Its how it was when i purchased it in the uk. Parts are not as easy to come by over here so may look at getting one shipped from rock autos. Yeh if i pump it up and hold it the peddle seems to stay there and not fade away.. it was a 2nd hand ms i fitted that my uncle had spare so no gaurentee its good.. thanks for the info..
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#9 |
Registered User
Join Date: Jun 2014
Location: lakefield,mn
Posts: 566
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Re: 68 c10 brake problems
That complete setup just looks wrong. I would fix it right then see what the problems are. Is that even a proportioning valve? Is it up side down and backwards?
The factory disc drum prop valve should look like this.
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68 c10 swb stepper 68 c10 swb stepper 67 c10 lwb 06 gmc duramax |
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