G Body Manual brake problem

Chipper Chapman · 09-06-2011, 08:16 PM

Having trouble with a spongy pedal, but no air in the system. It's got stock g body disc/drum brakes, with a Master Cyl for a 69 camaro manual disc/drum. I have removed the proportion valve. Relocated the master cyl rod pin up about 3/4" from the orig power location.

So now the problem is that I have a spongy pedal, with absolutely no air in the system. And it's giving me greif with staging more than anything, I have a 5200 flash stall converter, and 2400 rpm the car is trying to push the beams.

Is it possible the master is too small of a bore?

If not, any suggestions?

Alan Roehrich · 09-06-2011, 08:23 PM

Get a gauge and check the brake pressure.

I'd try a manual brake master cylinder from an S-10, the brakes are very similar, it'll be a plastic/aluminum master cylinder, get a syringe type pressure bleeder, you'll find them at O'Rielly's. You've definitely got the wrong master cylinder, in my experience.

Jeff Goss · 09-06-2011, 09:08 PM

I used a master cylinder for an 80-81 Trans Am for my 81 Malibu.

I can't remember exactly the reasoning, but the brakes held to well over 4500 on the footbrake, with a converter that stalled to 6100.

Hope this helps.

dahkahuna · 09-06-2011, 09:32 PM

Recently I did a conversion on a 66 chevy truck using a power brake booster, proportioning valve and dual master in a kit form based on a 69 camaro type unit. I spent hours trying to bleed the air out of the system using the old pump-it-up and hold the pedal pressure, then open the bleeder,without any sucess! Then I read the instructions on how to bleed that type system disc& drum and it said to open the closest bleeder and slowly push the pedal down to the floor and hold it , then close the bleeder. this centers the proportioning valve and lets the air move freely from the system. repeat the above directions paying attention to any air bubbles leaving each wheel, always check the fluid level to keep it full after each wheel is bled. Don'ty release the pedal till the bleeder is closed each time( remember no pumpin the brakes!

dahkahuna · 09-06-2011, 10:05 PM

By the way the front disc b leeder should be at the top of the caliper and you should be able to gravity bleed the front disc brakes with just pushing the pedal to start the flow they way I described. Hope this helps

Jody Lang · 09-06-2011, 11:12 PM

A big problem on these is when you remove the power brake can. The angle that the rod goes into the back of the master is off. Try to find an adapter plate that helps correct this angle.

I went with a Lamb unit. One great part of his is that the rod can't fall out of the back of the master.

09-06-2011, 08:16 PM	#1
Chipper Chapman Member Join Date: Jan 2004 Location: Belmont N.S. Canada Posts: 473 Likes: 246 Liked 166 Times in 71 Posts	G Body Manual brake problem Having trouble with a spongy pedal, but no air in the system. It's got stock g body disc/drum brakes, with a Master Cyl for a 69 camaro manual disc/drum. I have removed the proportion valve. Relocated the master cyl rod pin up about 3/4" from the orig power location. So now the problem is that I have a spongy pedal, with absolutely no air in the system. And it's giving me greif with staging more than anything, I have a 5200 flash stall converter, and 2400 rpm the car is trying to push the beams. Is it possible the master is too small of a bore? If not, any suggestions?

09-06-2011, 08:23 PM	#2
Alan Roehrich Veteran Member Join Date: May 2006 Location: Murfreesboro TN Posts: 5,118 Likes: 1,576 Liked 1,837 Times in 417 Posts	Re: G Body Manual brake problem Get a gauge and check the brake pressure. I'd try a manual brake master cylinder from an S-10, the brakes are very similar, it'll be a plastic/aluminum master cylinder, get a syringe type pressure bleeder, you'll find them at O'Rielly's. You've definitely got the wrong master cylinder, in my experience. __________________ Alan Roehrich 212A G/S

09-06-2011, 09:08 PM	#3
Jeff Goss Member Join Date: Nov 2001 Location: Burlington, WA Posts: 361 Likes: 1 Liked 0 Times in 0 Posts	Re: G Body Manual brake problem I used a master cylinder for an 80-81 Trans Am for my 81 Malibu. I can't remember exactly the reasoning, but the brakes held to well over 4500 on the footbrake, with a converter that stalled to 6100. Hope this helps.

09-06-2011, 09:32 PM	#4
dahkahuna Member Join Date: Jul 2006 Location: san dimas , calif Posts: 128 Likes: 0 Liked 5 Times in 3 Posts	Re: G Body Manual brake problem Recently I did a conversion on a 66 chevy truck using a power brake booster, proportioning valve and dual master in a kit form based on a 69 camaro type unit. I spent hours trying to bleed the air out of the system using the old pump-it-up and hold the pedal pressure, then open the bleeder,without any sucess! Then I read the instructions on how to bleed that type system disc& drum and it said to open the closest bleeder and slowly push the pedal down to the floor and hold it , then close the bleeder. this centers the proportioning valve and lets the air move freely from the system. repeat the above directions paying attention to any air bubbles leaving each wheel, always check the fluid level to keep it full after each wheel is bled. Don'ty release the pedal till the bleeder is closed each time( remember no pumpin the brakes!

09-06-2011, 10:05 PM	#5
dahkahuna Member Join Date: Jul 2006 Location: san dimas , calif Posts: 128 Likes: 0 Liked 5 Times in 3 Posts	Re: G Body Manual brake problem By the way the front disc b leeder should be at the top of the caliper and you should be able to gravity bleed the front disc brakes with just pushing the pedal to start the flow they way I described. Hope this helps

09-06-2011, 11:12 PM	#6
Jody Lang Member Join Date: Mar 2002 Posts: 306 Likes: 28 Liked 89 Times in 28 Posts	Re: G Body Manual brake problem A big problem on these is when you remove the power brake can. The angle that the rod goes into the back of the master is off. Try to find an adapter plate that helps correct this angle. I went with a Lamb unit. One great part of his is that the rod can't fall out of the back of the master.