Cadillac Repair/Brakes


QUESTION: I just got a 1983 Cadillac Deville Sedan, 4100 engine. Once when it was cold outside and once when it was warm, I start the car and push down the brakes and hear a air like sound and have no brakes. After I let it idled for about 10 minutes (both times) then the sound stops and the brakes work. Some kind of brake vacumn part? If so, where is it located and is it expensive part or labor cost expensive? The car has been sitting for a few years as the owner had died, except to start it from time to time so I heard there can still be some issues with a car that has been sitting. It might or not have something to do with the Service Soon light that comes on then off then again. though it don't stay on for long but enough to make me wonder why. Is there a computer Code to check problems?
Thanks for your time,

ANSWER: Hi Deborah,

Intermittent issues especial once hot, once cold are impossible to diagnose with any type of accuracy.
The cheapest guess though which I would recommend replacing would be the vacuum hose and check valve that goes into the brake booster at the firewall on the drivers side under the hood.
The valve is on the end of the vacuum hose and plugs into the booster.
Over years and engine heat, the rubber hoses get brittle and leak.
Here is the things you need to do with a car that old:

Change anti-freeze coolant. After 3 years it will turn acidic and rot the radiator and gaskets in the engine.

Change the fuel filter. Gasoline at the stations is of poor quality. Dirt an moisture accumulate and filter should be replaced every couple of years.

Transmission fluid, differential should be replaced.
Wheel bearings if applicable should be packrd.

Air filter should be checked.

Fuel injector cleaner with one bottle (no more) of heat should be put in a full tank to suck up any condensation in the tank.

Have battery and belts checked.

I would also suggest having brake fluid replaced and bled. Again, long term non use causes condensation in brake system, which could cause unsuspected failure.

If this vehicle is from the Midwest where road salt is used, check the brake and fuel lines for rust and replace as needed.

The worst thing for a vehicle is nonuse. If you don't do the recommended services, the vehicle will let you down and cost much more to repair in the future.

As far as you believing you had no brakes those times. You had brakes, but much more effort is
Required to depress the brake because your power assist is not functioning.

As for the check engine light: go to AutoZone and they can plug in a tester in into the vehicles computer port and tell you the codes and what they stand for.

The bad news is that this system had come out in 1982 and was very difficult to diagnose. In 1904, the OBD II system was introduced and still used today which could be diagnosed to pin point accuracy. Not true on the antiquated system in your car.

It could get very expensive to repair because instead of detecting a bad sensor, the complete circuit could be at issue. Codes also cascaded. A code 13 could set off a code 34 and a code 55.
Working on these new was a serious headache. The check engine light is for emissions. It will effect optimum power and mileage, but you can drive the car with the light on.
You have what is known as a soft code. The light may come on and go off. A code is set and you have 150 starts before the system recycles. I wouldn't worry about it.

---------- FOLLOW-UP ----------

QUESTION: Thanks. I did have coolant changed, oil changed, new belts et. Just wondered why the brake don't work right after twice in several times set to drive it didn't work and heard that air sound when pressed brake petal. then after running for 10 minutes, both times, brakes fully ok. Guess you said check for a vacumn hose leak. Wouldn't it do that each time start car? wondered why some times ok and sometimes not.
Thanks gain


You will never diagnose the problem with it doing what it did only twice. It's not happening!
In order to diagnose, the problem has to be there at all times, so you know you fixed it.
Anyone on the internet can give you a correction with certainty is a liar.
I have you the cheapest and most possible fix.
It's better than telling you that you need a new brake booster in which the rubber diagrams have rotted writhing.
You can't go used because of the same problem, and that will set you back about $500.
That is why I suggested the hose and check valve.
What you told me is that you had an intermittent vacuum leak, but without it being constant, all you can do is guess!


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Rob Painter


Alarm system questions cannot be answered on this forum. These systems are not what I can answer. Without being physically at the vehicle and not knowing what kind of electrical service has been done on the vehicle, there is no possible way to give an accurate answer over the internet. My expertise is in Ignition/key based anti-theft systems. These issues include GM VATS (resistor chip in key blade) PASSLOCK (MRD)-ignition lock rotation based, no special ignition key and the PKIII Transponder (computer chip in key) systems. These systems are not alarm based and are integral with the starting of the engine. This is why I cannot diagnose alarm problems without physically looking at the vehicle: Alarm systems are a completely different annimal than ignition key/lock based anti-theft system. Many alarm questions come from vehicles 10 years old, and since older, many hands that had been involved over the years.I am an expert in all GM factory (ignition/key based)systems. Alarm system questions pose to many situations beyond my knowledge as to what has been done to the vehicle over the years. Some guy may have actually wired the stereo into the alarm system. Who knows? Over my past 30 years in vehicle wiring repair, I have seen unbelievable wiring disaters done by guys that consider themselves "mechanics." I have seen stereos and alarms intalled using surgical tape. I have seen modules burn up, un-fused circuits, wiring jambed between the doors and even lamp cord used for a starter kill. To answer alarm questions over the internet without examining the vehicle is like asking; What does it take to remove a dent?


Education/Credentials-ASE certified. 11 years with a GM dealer and 17 years with a repair facility dealing with only the repair of theft recovered vehicles.

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