Help, help, help! I need some advice on my brakes. - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Blaze69 · 07-17-2003, 09:30 AM

Well it's been awhile since I last posted anything, I've been away too long. So here goes.

Some of you may remember that I was trying to convert my 69 over to disc. Well that part is done. Now I am having a hell of a time getting the brakes to bleed.

To start this off: Using the donors MC and combination valve the brakes did bleed and I DID have brakes that would work.....some of the time. I would have to pump them once before they would grab and then they would grab like hell.

I decided to change out the MC and valve with NEW units. Since that time I have little to no fluid coming out of the lines. The pedal goes to the floor with little force and no resistance. I have checked out the booster assist and I believe that to be o.k. Before putting the new parts on I did 'bench bleed" them.
My next course of action is replacing the new valve with the old one and trying it again. If that doesn't work then I will put the old MC back on and try it again. That is unless, someone out there has any other ideas or thoughts they would like to share.

I need to get my goat back on the road where it belongs.

JimKshortstep4x4 · 07-17-2003, 11:14 AM

It sounds like you have air in the system yet. I would try bleeding the prop valve by removing the front and rear lines and running temporary hoses back into the master cylinder. (Usually new master cylinders come with small hoses that you can adapt).
Submerge the hoses in the master cylinder reservoirs and pump away. This will bleed your master cylinder and prop valve at the same time. Once this is done rebleed the individual wheel cylinders.

Once you get air into the system it can be difficult to get it out.

Good luck!

Jim

Blaze69 · 07-18-2003, 08:48 AM

Hey Jim,
I've already tried that twice! There has got to be something that I am missing?????

MOTHERTRUCKERS · 07-18-2003, 09:12 AM

Check your rubber hoses to see if your getting full fluid thru them, they collapse inside and cause this problem sometimes.

JimKshortstep4x4 · 07-18-2003, 09:29 AM

Do you get fluid to come past the prop valve?

If you do, then check the fitting at the rear end to see if you get fluid at that point, (at the tee). The rear line being larger is harder to bleed and sometimes you have to do it in steps.

I am also wondering if your master cylinder is ok because it sounds as if you have been bleeding the system a lot.

Jim

ChevLoRay · 07-18-2003, 05:14 PM

A number of years ago, I bought a '38 GMC, in Tucson. The brake fluid had long since evaporated, leaving a dried-up concoction of of flaky stuff. Is there a possibility that one of your brake lines has experienced that? I make that suggestion not knowing how long any part of your system may have been open to the atmosphere.

I am sure you already know that bleeding the brakes should start with the wheel farthest from the master cylinder.

I also converted my '69 from drum to disc. It already had power brakes, but the master cylinder is new, and I believe it to be specific for disc brake usage. That may not be correct, but I believe disc brake master cylinders, in general, have slight differences from drum-only master cylinders.

Other than that, I don't know of anything else to offer. I am sure that it will be something simple but, as yet, undiscovered.

Gotta71C20 · 07-18-2003, 06:04 PM

You might check the master cylinder for the check valves that are used with disc systems. They are installed in the outlet ports for the brake lines. If they are there, leave them, if not, see if you can get some. They just tap in, or the fitting will seat them I believe. If they are missing, a little runout on the discs can knock thepads back, and push the fluid back into themaster cyl. Then when you apply the breaks, the pedal has to move the pad farther, and the pedal feels low. I know racers take the valves out, but I think they should be there. Larry

07-17-2003, 09:30 AM	#1
Blaze69 Registered User Join Date: Apr 2001 Location: Arizona Posts: 147	Help, help, help! I need some advice on my brakes. Well it's been awhile since I last posted anything, I've been away too long. So here goes. Some of you may remember that I was trying to convert my 69 over to disc. Well that part is done. Now I am having a hell of a time getting the brakes to bleed. To start this off: Using the donors MC and combination valve the brakes did bleed and I DID have brakes that would work.....some of the time. I would have to pump them once before they would grab and then they would grab like hell. I decided to change out the MC and valve with NEW units. Since that time I have little to no fluid coming out of the lines. The pedal goes to the floor with little force and no resistance. I have checked out the booster assist and I believe that to be o.k. Before putting the new parts on I did 'bench bleed" them. My next course of action is replacing the new valve with the old one and trying it again. If that doesn't work then I will put the old MC back on and try it again. That is unless, someone out there has any other ideas or thoughts they would like to share. I need to get my goat back on the road where it belongs. __________________ 1969 Blazer: 350/350, 4X4, HEI, Edlebrock carb/intake, dual flowmasters, np205, 3:07's and the rest is mostly stock. The front end disc swap is finally complete 2002 Z71 Tahoe. CAI, Flowmaster 40, Silverstars in high, low and fogs and a bunch of mods (upgrades) inside and out.

07-18-2003, 08:48 AM	#3
Blaze69 Registered User Join Date: Apr 2001 Location: Arizona Posts: 147	Hey Jim, I've already tried that twice! There has got to be something that I am missing????? __________________ 1969 Blazer: 350/350, 4X4, HEI, Edlebrock carb/intake, dual flowmasters, np205, 3:07's and the rest is mostly stock. The front end disc swap is finally complete 2002 Z71 Tahoe. CAI, Flowmaster 40, Silverstars in high, low and fogs and a bunch of mods (upgrades) inside and out.

07-18-2003, 09:12 AM	#4
MOTHERTRUCKERS Registered User Join Date: Dec 1999 Location: BRADENTON FLA Posts: 3,269	Check your rubber hoses to see if your getting full fluid thru them, they collapse inside and cause this problem sometimes. __________________ Rest in Peace Ed. Thanks for all the good times.

07-18-2003, 05:14 PM	#6
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	A number of years ago, I bought a '38 GMC, in Tucson. The brake fluid had long since evaporated, leaving a dried-up concoction of of flaky stuff. Is there a possibility that one of your brake lines has experienced that? I make that suggestion not knowing how long any part of your system may have been open to the atmosphere. I am sure you already know that bleeding the brakes should start with the wheel farthest from the master cylinder. I also converted my '69 from drum to disc. It already had power brakes, but the master cylinder is new, and I believe it to be specific for disc brake usage. That may not be correct, but I believe disc brake master cylinders, in general, have slight differences from drum-only master cylinders. Other than that, I don't know of anything else to offer. I am sure that it will be something simple but, as yet, undiscovered. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

07-17-2003, 11:14 AM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	It sounds like you have air in the system yet. I would try bleeding the prop valve by removing the front and rear lines and running temporary hoses back into the master cylinder. (Usually new master cylinders come with small hoses that you can adapt). Submerge the hoses in the master cylinder reservoirs and pump away. This will bleed your master cylinder and prop valve at the same time. Once this is done rebleed the individual wheel cylinders. Once you get air into the system it can be difficult to get it out. Good luck! Jim

07-18-2003, 09:29 AM	#5
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	Do you get fluid to come past the prop valve? If you do, then check the fitting at the rear end to see if you get fluid at that point, (at the tee). The rear line being larger is harder to bleed and sometimes you have to do it in steps. I am also wondering if your master cylinder is ok because it sounds as if you have been bleeding the system a lot. Jim

07-18-2003, 06:04 PM	#7
Gotta71C20 Registered User Join Date: Dec 2000 Location: Belfair, Wa. USA Posts: 80	You might check the master cylinder for the check valves that are used with disc systems. They are installed in the outlet ports for the brake lines. If they are there, leave them, if not, see if you can get some. They just tap in, or the fitting will seat them I believe. If they are missing, a little runout on the discs can knock thepads back, and push the fluid back into themaster cyl. Then when you apply the breaks, the pedal has to move the pad farther, and the pedal feels low. I know racers take the valves out, but I think they should be there. Larry



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