Starting a car after a 20-year hibernation

September 1, 2016 | By Staff


We have a 1976 Cadillac 4-door sedan Deville. It is a real sweetheart and is in very good shape. My problem is the engine hasn’t been run for over 20 years. Should we make any attempt to start it, and if so should we do anything special before trying to do so?


People often just put in a gallon or two of gas, a new battery, and then kick the engine over to see if it will start. It may or may not, but there is a good chance you will do damage to the motor if you try this. That’s because after 20 years, lots of things will need attention. Here is what I recommend: The first thing to do before trying to resurrect a classic that has been in storage for that long is to try to determine why it had been laid up in the first place. Many folks put old cars away simply because a water pump is bad or the brakes need re-doing. The old beast was most likely not worth much at the time, and a junkman wouldn’t even haul it away without charging for his efforts.

Cars hit bottom at about 10 years old and are often ready for some major work then too. If they survive the scrap heap, they usually slowly start going up in value until after 20 years when they often regain all they have lost and then some. In 1990 you couldn’t have given away a ’76 Cad four-door that had problems, but these days it would be a great car to own and drive.

It is possible the person who walked away from the car before you obtained it may have simply moved on or just never got around to starting it again. If that’s the case, do the following: Drain all of the old gas out of the tank and lines and put in fresh fuel. Change the oil and filter, and examine the contents of the oil. If it looks like chocolate pudding or has metal filings in it don’t start the engine until you fix the problem.

I would also clean or replace the air filter, and check the carb for dirt and residue in the float bowl. If the carb has sediment or dirt in it, I would install a rebuild kit before going further.

If the oil has coolant in it, usually it is because of a blown head gasket or cracked block or head. Don’t try to start a car with these problems. You’ll run the risk of causing more damage. If the oil looks normal, put a teaspoon of 10W30 motor oil down each spark plug hole and let it sit in there overnight so as to lubricate the cylinder walls and rings.

While you are waiting for the oil to soak in, drain the tranny and replace its fluid, and then change the lube in the differential too. Also—at the very least—you will need to purge the brake system of old fluid and replace it. In fact there is a very good chance you will need to do a complete hydraulic rebuild. It is also possible that, if the emergency brake has been cinched up for 20 years you could have a couple of stuck brake drums at the rear too. You can pop these loose by taking off the wheels, shooting in some alcohol-based cleaner, and then rapping on the drums with a large rubber mallet.

And with any car that has been sitting for 20 years, you should put in new cooling system hoses and belts before running the car. I would install a new thermostat just to be safe as well. Drain the old coolant if there is any left, and then flush out the system and put in fresh coolant. Examine the old coolant for muck and signs of oil contamination. These could mean head gasket or block problems too. Only when you are sure things are in good shape, should you start the engine.

Ground the coil high tension lead and then turn the engine over several times with the plugs out so it can get oil into its galleries without putting a load on the rod and main bearings. Now install the plugs and start the engine. The fuel may take awhile to get up to the carburetor, so be patient.

If the engine clatters and continues to do so, shut it off immediately. You could have one or more stuck lifters, in which case all of them should be removed and cleaned, rebuilt or replaced. If the lifters are OK and things sound healthy, warm the engine up, watching for leaks and problems. (It takes about 20 minutes to fully warm an engine. The temp gauge usually only tells you the head temperature.)

Now shut the engine off, remove the spark plugs, block open the choke and throttle, and do a compression check. The numbers should be within a couple of pounds of each other, and within eight to ten pounds of the compression specification in your shop manual.

If two adjacent cylinders are down on compression, check the head gasket on that bank and inspect for cracks in the head or block. If compression is low overall, shoot a little oil down the spark plug holes and test again. If the compression comes up, the rings are probably stuck or need replacing. If the compression stays low after the oiling, the valves or valve train probably needs work.

Finally, drive the car gingerly for a few days until the seals get wet, swell up and stop seeping, and you are sure you have remedied any minor problems. A little care upfront will go a long way toward avoiding disastrous damage to your classic.