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#1 |
Registered User
Join Date: May 2005
Posts: 212
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Brake bleeding questions...
I put new brakes on my '77, including new master cylinder, hoses, calipers, rear wheel cylinders, etc. The only things not touched were the proportioning valve, hard lines, and booster. I bench bled the master cylinder well (or so I thought), and have bled the lines a bunch. The brake pedal goes almost to the floor still. The brakes work, but not until they get towards the bottom. I'm pretty sure that this is an air-in-the-line issue, but I'm open to suggestions. Now that it's all together and this is the problem, what should I do? Any tips on bleeding the master cylinder again? I seem to get a push of fluid at the calipers with no air bubbles or sputtering of fluid. Anything else I should look at as well?
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Real Name - Brandon Current Vehicles: 1977 C20 Silverado 454/TH400 3.73s 1989 Jaguar XJ6 in the middle of an LT1/4L60E swap |
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#2 |
Hotwheels?
Join Date: Dec 2002
Location: Pleasant Hill, CA
Posts: 1,145
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Are they power brakes? Mine do that too ever since I touched them once to rebleed the lines, I dont think theres any air in the lines still, I bled them very thuroughly. Is there something I need to do to the booster?
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1978 Money Pit - CUSTOM DELUXE!!!! |
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#3 |
Registered User
Join Date: May 2005
Posts: 212
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Yeah, power disc up front, 13" drums in the rear.
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Real Name - Brandon Current Vehicles: 1977 C20 Silverado 454/TH400 3.73s 1989 Jaguar XJ6 in the middle of an LT1/4L60E swap |
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#4 |
Registered User
Join Date: May 2005
Posts: 212
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Anyone....?
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Real Name - Brandon Current Vehicles: 1977 C20 Silverado 454/TH400 3.73s 1989 Jaguar XJ6 in the middle of an LT1/4L60E swap |
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#5 |
Until Seventy Times Seven
Join Date: Feb 2005
Location: Rocky Mountain Front Range
Posts: 1,301
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Do you have a metering pin on your combination value? I had to depress mine to hold open the combination value to correctly bleed the system.
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boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin... |
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#6 |
Overcamber
Join Date: Mar 2005
Location: Skead ,Ontario
Posts: 109
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make sure your rear brakes are adjusted up as well..makes a big differencel
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#7 |
Registered User
Join Date: May 2005
Posts: 212
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I have no idea on the metering pin on the combo valve. I don't even know what to look for. Any help here would be good!
As far as the rear brakes, I adjusted them to just slight drag, which has always been good on other cars.
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Real Name - Brandon Current Vehicles: 1977 C20 Silverado 454/TH400 3.73s 1989 Jaguar XJ6 in the middle of an LT1/4L60E swap Last edited by Earl Filter; 06-27-2005 at 08:08 AM. |
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#8 |
Until Seventy Times Seven
Join Date: Feb 2005
Location: Rocky Mountain Front Range
Posts: 1,301
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I don't know if your '77 has the same combination valve as the 83. The combination valve is mounted on the front cross backet between the frame rails under the shroud on the driver side opposite of the steering gear box.
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boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin... |
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#9 |
Registered User
Join Date: May 2005
Posts: 212
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I do believe that it's the same combo valve, or similar. So I push in on the pin while bleeding? I haven't seen this part of the procedure. Thanks for the diagram!
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Real Name - Brandon Current Vehicles: 1977 C20 Silverado 454/TH400 3.73s 1989 Jaguar XJ6 in the middle of an LT1/4L60E swap |
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#10 |
Registered User
Join Date: Apr 2005
Location: Tulsa Oklahoma
Posts: 943
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Please Explain The Metering Pin In More Detail Its Veg To Me Just Press It In Before,after, During, Bleeding Brake? I Dont Know What It Does
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square body trucks an addiction or an investment either way they consume all my extra time and money |
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#11 | |
Happy to be here
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Location: Cypress, TX
Posts: 39,023
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Quote:
It sounds like you may have air trapped up stream though.... ![]()
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Follow me on Facebook and Instagram @N2trux.com Articles- "Jake" the 84 to 74 crewcab "Elwood" the77_Remix 85 GMC Sierra "Scarlett" "Refining Sierra" |
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#12 |
Until Seventy Times Seven
Join Date: Feb 2005
Location: Rocky Mountain Front Range
Posts: 1,301
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As I understand it, the metering valve affects the front circuit of the brakes. It's function is to allow some pressure build up on rear wheel cylinders before the front disc calipers are applied somewhere between 70 to 120 psi.
I was able to wedge a block of wood between the frame and the metering pin to keep it depressed. Then, the manual process of bleeding the system can begin. You probably followed the procedure below, but I'll list it again just in case you missed something (or I ![]() It's important to maintain at least 1/2 full of fluid in the master cylinder at all times otherwise air may be re-introduced back into the system. 1. Release the vacuum reserve by applying the brakes several times. (Engine off.) 2.To bleed the master cylinder: 2a. Disconnect the forward brake tube connector at the master cylinder. 2b. Allow the fluid to fill the master cylinder bore until it flows from forward brake tube port. (Contain the excess fluid.) 2c. Connect and tighten the forward brake tube connector to the master cylinder. 2d. Depress the brake pedal slowly and hold. Loosen the forward brake tube connector at the master cylinder to purge the air from the bore. Then tighten the connector and slowly release the brake pedal. 2e. Wait 15 seconds. 2f. Repeat steps 2d and 2e, until all air has been removed from the bore. (Be careful not to get the fluid on painted surfaces.) 2g. Repeat steps 2a thru 2f for the rear brake tube connection. 3. Bleed the calipers/cylinders in the following sequence: - Right rear wheel cylinder. - Left rear wheel cylinder. - Right front wheel caliper. - Left front wheel caliper. For each cylinder/caliper: 3a. Attach clear tubing over the bleeder valve (screw) and submerged the other end in a glass/clear plastic bottle partially filled with fluid. 3b. Depress the brake pedal slowly and hold. Loosen the bleeder valve to purge the air from the caliper/cylinder. (Observe the air bubbles thru the tube and bottle.) Then tighten the bleeder screw and slowly release the brake pedal. 3c. Wait 15 seconds. 3d. Repeat steps 3b and 3c, until all air has been removed. I had to repeat the sequence quite a few times (about 1/2 dozen times) to completely remove all air from the lines. Repeating the sequence a dozen or so times is not uncommon. BTW, don't forget to remove the block of wood after completing the process. The full shop manual write-up is on Jeff's site at Bleeding Brake Hydraulic System. Good luck. Let us know how it goes.
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boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin... |
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#13 |
Right turn Clyde
Join Date: Nov 2002
Location: Cincinnati, Ohio
Posts: 2,911
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I used a wide thick zip tie on mine to depress the valve.
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1974 C25 LWB: 454 4bbl Carb / TH400 / 3.73 1992 Camaro RS 305 TBI |
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#14 |
Registered User
Join Date: May 2005
Posts: 212
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I believe that this will take care of the problem. Thanks for the details. I'll do it this weekend, and see how it goes.
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Real Name - Brandon Current Vehicles: 1977 C20 Silverado 454/TH400 3.73s 1989 Jaguar XJ6 in the middle of an LT1/4L60E swap |
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