1970 Deville hydraulic brake questions

[chrisntam]

Well, driving the ol' car around today and as I'm pulling in the driveway, the brake pedal goes to the floor.      Check the master cylinder, the back reservoir is down a bit, add some fluid and no change.  I'm seeing some fluid loss on the booster under the MC.  Booster and MC are likely original and pretty nasty looking.  Looked at the calipers/wheel cylinders, don't see any fluid (from the outside), is it likely the master cylinder took a dump?  Pedal goes to the floor, brake warning light comes on (yeah! that warning system is working!)  Looks like it's time to go through the brakes, been putting it off, they have been working ok, though it looks like that is at the top of the list now.  I bought a booster/master cylinder last year so at least I have those two items.

Along with all that, has anyone used ceramic brake pads?  I hear the brake dust is greatly reduced with ceraminc pads.

Also, anyone know off hand if the rear drums are 12 inch?  Just need to look in the FSM.........

RockAuto, here I come! 

[76eldo]

I would use premium regular pads, not ceramic.  Brake dust is not really an issue on a 70 with a big old steel wheel and a full wheel disc.

Brian

[dplotkin]

....the brake pedal goes to the floor...Check the master cylinder, the back reservoir is down a bit, add some fluid and no change.  I'm seeing some fluid loss on the booster under the MC.  Booster and MC are likely original...

The rear seal of your master has failed. Brake fluid is leaking into your booster where it is eating up the rubber diaphragm. Engine vacuum is sucking & burning some of the fluid. This is a classic failure and why it is highly recommended to rebuild or replace a booster any time a master is replaced. Not a lot of analysis or rumination needed here, replace both, flush system & inspect or replace wheel cylinders. A munged-up master usually means the wheel cylinders are in similar shape, all of which can lead to a hurtling 5,000 pound Caddy that cannot stop in time.

Dan

[TJ Hopland]

I'm with Dan.   Likely the age of the rubber parts and contamination of the fluid has got to it.  I also agree with the thought that the calipers / wheel cylinders are likely in the same shape so if you are going in you might as well get everything done including hoses. 

[35-709]

FWIW, I'm with TJ and Dan.  Good thing that happened in your driveway for the sake of yourself, some other innocent person(s), and your car!  Brakes are never something to delay maintenance on.

[Scot Minesinger]

If you are on original brake system:

1.  Obviously master and booster need to be replaced.
2.  Rubber brake hoses if original or history unknown (3 total) need to be replaced
3.  Pistons/calipers on all four brakes if original or history unknown need to be replaced
4.  I would also replace all of the steel original brake lines including and especially the front to back section (U-line tubes makes a replacement), as these steel lines rust from inside out.  The new lines have a tough inner liner of brass alloy or some kind that will not rust. 
5.  Sometimes the springs on emergency brake cables loose their spring strength and those need to be replaced too, but the main cable that connects to emerg. pedal is often still good.

Oh and yes you are so lucky the failure happened in a driveway! My master on SDV started to fail gradually and the brake warning light glowed, so replaced all of the 5 things above, now it stops great with no warning light glowing.

[Bobby B]

I would use premium regular pads, not ceramic.  Brake dust is not really an issue on a 70 with a big old steel wheel and a full wheel disc.

Brian

In agreement with Brian. A good factory style carbon/ semi-metallic pad up  front, with an organic style composition rear shoe is fine. Ceramic pads are great on modern cars with open style aluminum rims as far as the dust/noise issues go.  Plus, they are easy on your new Chinese rotors that need replacing every time you do a pad change now.   I use them on all of our modern cars. The only drawback to them is that they don't grab as quickly when cold, but they do have a nice progressive bite once they heat up. You just have to be aware on cold days not to do any high speed drafting until they heat up…….
                                                                                                               Bobby

[chrisntam]

Hey Scot - how difficult are the steel lines to get to?  My car came out of New York ( just a mild amount of corrosion under the car - body was undercoated) and I am concerned about breaking the flare nuts loose from the brake hoses/cylinders, etc.  I guess I'll know real quick if they are corroded........  Did you mean "inline tube"?  Googled "u-line" and "inline tube" came up.

Who doesn't love working on cars in the TEXAS heat?   

Will be replacing master cylinder/booster, calipers, wheel cylinders, hoses, pads/shoes, new hardware.  On the fence about the steel lines, but I'll look into it.  I ordered wheel bearings, will check the country of origin prior to installation.   

Don't want to turn the rotors and lose thickness.  Should I scuff them with crocus cloth / sandpaper?  Same thing with the drums?  Don't want to needlessly lose metal unless absolutely necessary.

chris.

[35-709]

The rotors and drums should at least be measured against factory limits which are usually stamped right on the drums or rotors.  A well equipped parts store, a machine shop or an auto service facility can measure them easily if you take them there.  Any grooves or warpage means they should be turned as a necessary and important part of a proper brake overhaul, if you get a vibration upon braking after you are all finished you will have to take it all apart again.  Warped drums and/or rotors decrease braking effectiveness, create more heat, and cause vibration sometimes not noticeable until new pads or shoes are installed. 

If you are going to do it, do it right, brakes and steering are two of the the most important parts of your car.  Don't skimp on your brakes to save a few bucks, definitely a false economy!  Replacement drums and rotors, if needed, are easy to come by at your parts store or certainly from Rock Auto.

Any little scratching you could do with sandpaper will be a waste of time and effort and will be smoothed off almost immediately when you use your brakes.