Hi all, I need some advice.. I have a 65 Olds Cutlass power drum brakes all around with single reservoir master cylinder. I recently converted to a dual reservoir master. Tha car now stops like crap. Almost feels like just the rear brakes are activating. Both masters have a 1inch bore. Pedal is firm no air in line. Any thoughts or advice? The front brake line is on the rear port and rear brake line is on

65 Olds
the front port on master. Not sure if there is different pressure on front or rear ports or if they are the same?

 

I'm not that familiar with that conversion, but the above just sounds wrong. Did you use a new proportioning valve? Pics and a more detailed description of your conversion will help diagnose the problem.

 

Did you change the pushrod when you swapped master cylinders?

 

WHICH dual reservoir M/C did you use? Did you retain the original 9" brake booster? Did you check pushrod length vs the depth of the hole in the M/C piston?

 

He has 4 wheel drum so would it even have a pro valve?

 

NO! About the only four wheel drum car that I am aware of that used a prop valve was the first gen Toronado, likely due to the unusually high front weight bias.

 

Hi All,
Before putting in the new master I did measure the depth of the master piston to the depth of the old master and they were the same. I did keep the 9" brake booster. I think the problem is the booster failed. Im getting vacuum from the manifold. When I bleed the vacuum from the booster and apply brake pedal, start the engine to build vacuum the pedal doesnt sink. Not sure why this would fail after I put the double reservoir master on??? FYI the rear brake line goes off the front port directly to the rear brakes. The front brake



line goes from the rear port to the distribution block, then branches off to the right and left brakes. This is the description of the new master. Anyone know where the best place to buy a 9inch boosterDescription:

• For Drum/Drum applications
• Will Work for Either Manual or Power Brakes
• Cast Iron Master Cylinder Double Bail Power
• 1" Bore
• 9/16" and 1/2" ports

 

Drive the car with the booster connected and again with the booster vacuum line disconnected and plugged. If the brakes feel different, the problem is not the booster. Did you install the rubber gasket between the M/C and booster? This is required to seal the front side of the booster diaphragm.

 

While I never had to use one of these tools when servicing the brakes on my Oldsmobile. It might be a good idea to get one and check the depth/throw of your vacuum booster to make sure it isn't keeping your master cylinder activated. Or failing to activate the master cylinder fully.

https://www.speedwaymotors.com/Maste...ol,583777.html

FWIW, I bought one much cheaper on Amazon when I serviced the brakes on my 86 Ford F250.

 

I will try the vacuum line first. I did not install the rubber seal as it was torn. If the seal wasn't installed wouldn't I hear vacuum leak or engine stumbling ( Vacuum Leak ) I will hunt one down and replace anyway. Thank you

 

I used the tail end of a vernier scale to measure depth. Thank you cool tool!

 

Well I think you are onto something with the rubber boot. I started the car and sprayed some starting fluid were the MC meet the booster... Sure enough I had a rise in RPM's. Would anyone know where I can source a new boot/seal?

 

Call Karp's Power Brakes. He is one of the best at rebuilding brake parts. He may be able to sell you the seal. Here is a link.

Home - KARPS POWER BRAKE SERVICE & CYLINDER SLEEVING

 

Great! Thank you all for the assistance

 

For future reference, GM was not in the habit of installing parts that were not necessary.