Brake Question???????

[66 Red Rocket]

Today was forcast to be 70° so I desided it would be a great day to drive the vette. When I went to meet my best friend for lunch I was stopping at a traffic light and the brake pedal just went to the floor, boy that will wake you up. Initially I had good pedal and it went to nothing. Well got her stoped with downshifting with the engine off. I checked the master cyl and the front portion of the master cyl was prety low, with the bellows(in the cap) fully extended. I returned the bellows to norman position and pumped the brakes too look for puddles. Zero puddles and dry calipers. When we finished lunch I desided to try to get it home while the traffic was a minium. Well here is the strange part, the pedal was as hard as a rock and everything was back to norman. Can anyone explain this to me. I have a 67 dual master on my 66. Thanks, John

 

[IH2LOSE]

I suggest you dont drive that car again until you figure out what hapened,

I know its hard to do but My first reaction is always the emergency brake to make a stop,

Me pesonally am a saftey freak and would rebuild that entire system

As for your problem,when was the last time this system was rebuilt

Brake system= steel lines,soft hoses,calipers.pads,rotors,master cylender,

If its all recently done (last 10 years)I would suggest a thurow inspection of the items I outlined above ,paying special attention to any steel lines tha may have the slinky type outer coating on them.they seem to trap water and rust the steel out with out you seeing it.I would check all soft hose.and replace any thing over 10years old on them. Use a flash liglht to look up into the caliper area for weepage,

I use a motive power bleeder,Makes real easey work of bleeding brakes if its used correctley,I say this because my next suggestion to you is to actually bleed the brakes,Until I got my motive power bleeder I hated to bleed the brakes on a midyear and it would end up being a 3 day job to bleed them.Know with the power bleeder its a 40 minute one man PERFECT BLEED!.

The power bleeder also finds leaks fast,and bad hoses Last year I bled the brakes for a shop who does my truck inspection,They replaced a steel line on a customers C3.They knew I was into vettes and asked my advice on how to bleed.I ran up and set up the bleeder.put it under pressure and theft it on under pressure,I was doing my normal saftey check of all the brake lines and looking for leaks,When I noticed the soft line was exspanding in the front right,(like a small blister in the hose) well they called there customer and the ended up doing an entire brake rebuild,


I realley have to stress DONT DRIVE IT,untill you find the problem.

Good luck

 

[mike weyman]

get it up in the air, fill the resevoirs ,and pump till it squirts. there is a safety part in the system(forget what it is called)that blocks the leaking brakes(front or back)when the pressure drops the part actually closes off the leaking brakes.this would account for you now having brakes, i would say you now only have back brakes.

 

[Vetsvette2002]

The 67 MC does NOT have any safety valving. It uses different sized orafices to provide for front and rear brake bias or porportioning. There is a low pressure switch that will illuminate the tattletale light on the dash on a 67, the 66 does not have this circuit.
So do NOT DRIVE it until it is fixed.

 

[XJ6GUY]

i had that happen to me once.the fluid was so low that when i applied the brakes it pulled the bellows over the fluid hole and starved the the cylinders of fluid.i was told it was from someone adding fluid to the master without pushing the bellows back up....tom