70 brake problem cont.
Thread Starter
Instructor
Joined: Sep 2005
Posts: 122
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70 brake problem cont.
still trying to get some life in the system. I put on a new master cylinder, bled it properly I think. changed acaliper that was suspect leaking. I get the weakest pedal when I try to bleed the system. I do all this with the engine off. Now I apply slight pressure to the pedal, hold the pedal down with light pressure and start the engine. As soon as it fires up the pedal goe down to the floor and there is no pedal at all. it is as if the linkage was disconnected. Any ideas for the next step?
the car has power brakes
the car has power brakes
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
A faulty booster will make the pedal harder to press because it will not provide any assist. A leaky/faulty booster is not going to cause your pedal to go to the floor.
Buy or make 2 inverted flare plugs for the master cylinder line ports. You can buy 12" sections of brake line at an autoparts store with the correct fittings, cut one end off about 2 inches long, and hammer the tubing shut with the nut installed. These make good test plugs. remove the brake lines, and install both plugs... press the pedal. If it goes to the floor, with or without booster assist, then the M/C is faulty (or needs to be re-bled).
New and/or rebuilt master cylinders that have been sitting on the shelf in a store or warehouse for several years will have rust on the inside... they are faulty and will not work. I disassemble ALL new/rebuilt master cylinders before I install them.... saves a lot of time & grief. Many of them for the older muscle cars are already rusted on the inside.
If the pedal stays good, reconnect the lines and focus on the rest of the system.
If not, re-bench bleed the master using the correct method.... tubes running from each port back to the master cylinder while you pump the cylinder until the cylinder is bled.
Retry the plugs... if the pedal still goes to the floor, the M/C is bad.
Buy or make 2 inverted flare plugs for the master cylinder line ports. You can buy 12" sections of brake line at an autoparts store with the correct fittings, cut one end off about 2 inches long, and hammer the tubing shut with the nut installed. These make good test plugs. remove the brake lines, and install both plugs... press the pedal. If it goes to the floor, with or without booster assist, then the M/C is faulty (or needs to be re-bled).
New and/or rebuilt master cylinders that have been sitting on the shelf in a store or warehouse for several years will have rust on the inside... they are faulty and will not work. I disassemble ALL new/rebuilt master cylinders before I install them.... saves a lot of time & grief. Many of them for the older muscle cars are already rusted on the inside.
If the pedal stays good, reconnect the lines and focus on the rest of the system.
If not, re-bench bleed the master using the correct method.... tubes running from each port back to the master cylinder while you pump the cylinder until the cylinder is bled.
Retry the plugs... if the pedal still goes to the floor, the M/C is bad.
Last edited by Tom454; Sep 28, 2005 at 01:55 PM.
