"72 Cadillac Brake booster issue

[Bill Young]

Does anyone else experience a hissing sound like escaping vacuum or air when you press on the brake pedal from their booster? I do on My '72.

[TJ Hopland]

I have had them that did that and seemed to be alright for a few more years.  If they start hissing when you are not on the brake it could be a bigger issue since its essentially a vacuum leak.   Always thought about repairing or replacing them but other things ended up killing the vehicles before the booster ended up being a real issue. 

[Scot Minesinger]

Replace your brake booster, it is leaking slightly, but it is on the way out to total failure.  While doing if mater cylinder is original or unknown history might as well replace too because it has to be removed to replace booster.

["Cadillac Kid" Greg Surfas 15364]

Bill,
For what ever the reason I thought my brake booster on my 72 (eldo) was making too much noise a year or so after I bought it (new in 71), and replaced it with a new (not rebuilt) booster.  The same sound reappeared, and was still there 40 years later when I sold the car.  Noise is subjective, and the older devices were much more audible than new cars. 
Greg Surfas

[dplotkin]

Bill:

Scot is correct. Replace your booster now. It is not failing. It has failed. It will soon quit altogether leaving you with marginal braking for a very heavy car. The pedal linkage and height is designed for power brakes. With no booster working you cannot apply the same mechanical and un-boosted leverage with your foot.

Besides, you now have a vacuum leak which is leaning out your mixture and is or will shortly cause a rough idle and could burn a valve.

Fix it. Now.

Dan

["Cadillac Kid" Greg Surfas 15364]

There you have it Bill. Opinions range from disaster to denial.  You did not mention that you are having a problem with your brakes. Are you?
Greg Surfas

[Bill Young]

Again I am appreciative of the advice. With regard to the question about present braking. My brakes seem perfect. However that does not say the booster could not fail tomorrow. So that said , If I replace the booster I do NOT want some made in china or mexico junk. Where can I purchase a quality one and what am I looking down the barrell at?
Bill

[bill06447]

You can buy a Cardone reman unit with master cylinder (rebuilt in Philly) for around $100 from Rockauto. Google for a 5% discount code.

Bill

["Cadillac Kid" Greg Surfas 15364]

Bill,
If you do replace the booster, pay attention to the way it seals at the firewall and be sure it is re-sealed adequately to prevent water leaks and the intoduction of engine compartment fumes.
Greg Surfas

[Scot Minesinger]

The combo booster/master cylinder is the way to go.  Mine is a Cardone, but others will work too.  While your brake system is apart it I always a good idea to replace the rubber hoses (three, one in rear) and blow out the metal lines with compered air.

[dplotkin]

You can buy a Cardone reman unit with master cylinder (rebuilt in Philly) for around $100 from Rockauto. Google for a 5% discount code.Bill

Agreed. you may also send it out to be rebuilt by a variety of guys including Ed Strain & "Booster Dewey."  I've used both. The advice to replace the master cylinder at the same time is very wise. Besides use & age it is a leaking rear master cylinder seal that allows brake fluid to permeate the rubber diaphragm in the booster & degrade it. Always best to change the master at the same time. Remember, boosters are consumable items in a car, with a definite lifespan, like hoses & spark plug wires, things made of rubber.

Dan 

[Bill Young]

I have ordered a rebuilt cardone unit with master cylinder from Rockauto. I will have them installed as soon as I receive them. Again thank you all for your concern and advice.

[Bill Young]

OK, I have had the brake booster and master cylinder both replaced. Now when I apply the brakes it still hisses exactly the way it did before. Is this normal? I do not remember My Mothers 1971 Eldorado Convertible doing this back in the day.

["Cadillac Kid" Greg Surfas 15364]

Bill,
Without repeating my earlier post, some sound is normal. Perhaps since convertibles are slightly noisier than coupes you did not hear the sound.  Over the years my motto has definitely become "if it ain't broke, don't fix it".  Seems especially true on our Cadilacs.  They seem to have been so "over engineered" that most failures are announced way before they happen.
Greg Surfas

[TJ Hopland]

Over the years my motto has definitely become "if it ain't broke, don't fix it"

Another reason to follow that rule it seem like a lot of the parts available today are junk right out of the box. 

[Bill Young]

OK Guys thank You. I will live with it I guess. My 1961 makes no sound when the brakes are applied.

[joecaristo]

I know this has nothing to do with brakes but you can always check the vacuum hoses underneath the dash. Cruise, and climate control run on vacuum. My Eldo was making a hissing noise and I found the hoses on the back of the climate control switch were loose.

[Scot Minesinger]

Bill,

I just replaced my brake booster and master cylinder, fortunately that was the answer to my no power on brakes issue.  It is difficult to diagnose over the internet.  I had no vacuum issues so put up a post questioning it.

Thought occurred to me.  You probably have cruise, could it be the cruise control system that has a vacuum switch on brake.  Disconnect that hose at engine compartment and see if hiss happens when you step on brake.

If you need to replace that hose: You can attach a vacuum hose coupling to end of vacuum hose in engine compartment to new role of hose and pull old hose from under dash thru until new hose coupled to old emerges and that is a clean way to replace the fire wall penetration vacuum hoses.

[Glen]

Do these boosters have filters/mufflers to clean the air and muffle the sound?  Maybe the filter/muffler is missing. 

Just a thought.

[Coupe Deville]

Hello Bill. It is a little late to say this but my 1972 CDV has made the same exact noise you are describing ever since I had the car. My booster/master are original. It is a hissing sound from inside the car only when the brake pedal is being pushed down. If I hold constant pressure no hissing noise is made. Only on application it makes noise....For what its worth.

-Gavin