Brake Help !
Thread Starter
Instructor
Joined: Sep 2007
Posts: 244
Likes: 3
From: Long Island
Brake Help !
70 vert, NO POWER BRAKES, Went for a drive, after about the forth stop, brake pedal went to the floor. Got the car home, no visable leaks at the wheels. Checked the master cylinder, fluid level was still topped.
Rubber diaphrams were extended
Bad master cylinder??????????????
Rubber diaphrams were extended
Bad master cylinder??????????????
Burning Brakes
Joined: Sep 2009
Posts: 1,124
Likes: 140
From: Western New York
Definitely sounds like a bad master cylinder. You've had an internal seal failure. Time for a rebuild, a rebuilt, or a new master. I had the same thing in my '72, with no power brakes. I rebuilt my original master cylinder, and it was really inexpensive and easy. Give it a try.
Thread Starter
Instructor
Joined: Sep 2007
Posts: 244
Likes: 3
From: Long Island
Definitely sounds like a bad master cylinder. You've had an internal seal failure. Time for a rebuild, a rebuilt, or a new master. I had the same thing in my '72, with no power brakes. I rebuilt my original master cylinder, and it was really inexpensive and easy. Give it a try.
Thanks !!
Burning Brakes
Joined: Sep 2009
Posts: 1,124
Likes: 140
From: Western New York
The 2 nuts come off and the studs stay in place. I'd replace the gasket between the master and the firewall, as long as you have it off. Whether you go with Autozone or Zip depends on how fast you want to get it back on the road. Keep your current master, if it's original. It will have 2 bleeders on the side, unlike a replacement which may not have the bleeders. Make sure you bench bleed thoroughly before installing, so you don't have a soft pedal when you're done. Good luck!
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
On your drive did you go fast ? If so you might want to try bleeding the calipers first and see if there is air in them , start with the rear . If you have too much rotor runout the calipers could have sucked air. If you do find air , note the caliper and then check runout on that wheel.
Race Director
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From: Out Where the Buses Don't Run, Eglin AFB/ Niceville FL
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On your drive did you go fast ? If so you might want to try bleeding the calipers first and see if there is air in them , start with the rear . If you have too much rotor runout the calipers could have sucked air. If you do find air , note the caliper and then check runout on that wheel.
Air in the calipers will have the same effect. I had an 82 that would lose pedal every three months. The first time in happened I thought it was the MC and had it replaced. Three months later, no pedal. I had a shop check the run out and it was slightly out. We re-shimmed it but the problem persisted. I milked it until something showed as a sign of the problem. Eventually the left rear caliper started to show signs of a leak. Put in new seal kits on all four calipers and all was well for the rest of the time I had the car.
Thread Starter
Instructor
Joined: Sep 2007
Posts: 244
Likes: 3
From: Long Island
On your drive did you go fast ? If so you might want to try bleeding the calipers first and see if there is air in them , start with the rear . If you have too much rotor runout the calipers could have sucked air. If you do find air , note the caliper and then check runout on that wheel.
Le Mans Master
Joined: Jan 2007
Posts: 5,485
Likes: 7
From: Peekskill NY
My vote is the master cylinder. I have a similar symptom, though not as bad as yours. I've had this happen on several older cars in the past and the MC was the reason.
I just bought a correct repro Delco MC from ZIP. I have manual brakes. I took advantage of their Carlisle 10% off & free shipping deal. They have the lowest price for this MC that I could find. I also had checked out Auto Zone and didn't like the MC's they had, visually.
Glenn
I just bought a correct repro Delco MC from ZIP. I have manual brakes. I took advantage of their Carlisle 10% off & free shipping deal. They have the lowest price for this MC that I could find. I also had checked out Auto Zone and didn't like the MC's they had, visually.
Glenn
Last edited by GD70; Sep 11, 2010 at 07:09 PM.
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Thread Starter
Instructor
Joined: Sep 2007
Posts: 244
Likes: 3
From: Long Island
My vote is the master cylinder. I have a similar symptom, though on as bad as yours. I've had this happen on several older cars in the past and the MC was the reason.
I just bought a correct repro Delco MC from ZIP. I have manual brakes. I took advantage of their Carlisle 10% off & free shipping deal. They have the lowest price for this MC that I could find. I also had checked out Auto Zone and didn't like the MC's they had, visually.
Glenn
I just bought a correct repro Delco MC from ZIP. I have manual brakes. I took advantage of their Carlisle 10% off & free shipping deal. They have the lowest price for this MC that I could find. I also had checked out Auto Zone and didn't like the MC's they had, visually.
Glenn
Thread Starter
Instructor
Joined: Sep 2007
Posts: 244
Likes: 3
From: Long Island
Le Mans Master
Joined: Nov 2001
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From: LONG ISLAND
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i got a "GM" restoration part ( M-CYL ) from a company for $145 with free shipping...........
Thread Starter
Instructor
Joined: Sep 2007
Posts: 244
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From: Long Island
Zip was $110 plus $16 shipping - brand new reproduction
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
I've found many 1 1/8 on non power cars,they stop like crap.
Its not uncommon for the wrong one to be sold and shipped.
Thread Starter
Instructor
Joined: Sep 2007
Posts: 244
Likes: 3
From: Long Island
Thread Starter
Instructor
Joined: Sep 2007
Posts: 244
Likes: 3
From: Long Island
Okay here's where I'm at. Checked the bore size on the new MC and it is 1" (good). Bench bleed the new MC purchased from Zip. Installed in car and bleed through bleeder valves on MC. Started wheel bleeding (RR inner bleeder, RR outer bleeder, RL inner bleeder, RL outer bleeder, FR then FL. Pedal was wonderful. Drove 10 minutes or so and pedal sunk again when stepping on clutch and brake at a light. The difference this time versus when all of this started is, while in the process of braking, I can pump and get brake pedal back. Got the car home, checked MC level, still at proper fill. Appreciate your feedback - Thanks
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Okay here's where I'm at. Checked the bore size on the new MC and it is 1" (good). Bench bleed the new MC purchased from Zip. Installed in car and bleed through bleeder valves on MC. Started wheel bleeding (RR inner bleeder, RR outer bleeder, RL inner bleeder, RL outer bleeder, FR then FL. Pedal was wonderful. Drove 10 minutes or so and pedal sunk again when stepping on clutch and brake at a light. The difference this time versus when all of this started is, while in the process of braking, I can pump and get brake pedal back. Got the car home, checked MC level, still at proper fill. Appreciate your feedback - Thanks
Thread Starter
Instructor
Joined: Sep 2007
Posts: 244
Likes: 3
From: Long Island
I would rebleed the calipers starting with the rears and see if you get more air ,note caliper or calipers with air. If your pedal is back ,drive car again (carefully) and if the pedal goes bad again ,check the noted calipers for more air. If you have air back in the same calipers you most likely have too much rotor runout on those calipers. This is not uncommon with the installation of new rotors.