What's That Smell?

Today, I pushed the car out of the garage, set it up on jack stands, got underneath and (eventually) removed the gas tank.  This is actually significant, since the fuel line to the gas tank is one of those things that usually freezes up solid on old cars.  I used a little WD-40, then a heat gun until it just started to smoke a little.  This expanded the fitting so that I could actually loosen it, and the deed was done.  As far as I could tell before removing it, the tank was empty.  Actually, it had a small amount of a thick, very smelly syrup that used to be gasoline.  Upon removing the tank from the car, I couldn't help but notice some rather conspicuous rust holes in the top of the tank.

Of course the rust holes are in the top of the tank... the bottom was coated with gas-syrup, which probably provides good rust protection!  In any event, I have added "gas tank" to the list of new items I need to procure.

The smelly gas-syrup and the holes got me thinking.  This car smelled bad 30 years ago, and I noticed when I got it in my garage last April that it still smelled bad.  I figured it was 20+ years of road grime, stuck to the bottom of the car by a thin layer of engine oil from the road draft tube (more about that in a minute).  Now I'm wondering if this stench has been coming from the sponge-bob gas tank all along!

Tech Alert!  If you are a gear-head, I'm sure you will find this fascinating! If not, please skip to the next post.
Now a word about crankcase ventilation.  Before 1962, virtually all cars used a simple tube to vent exhaust bypass gasses from the crankcase.  Blow-by happens because the piston rings aren't perfect at holding in the gas-air mixture during compression, or the burning gas-air mixture during combustion.  Since these gasses are mostly hot gasoline vapor and air, some very bad things can happen when you let them build up in a confined space like an engine crankcase!  In the case of the t-bird, the "road draft tube" that vented these gasses led to the bottom of the car, right behind the engine.  Besides blow-by gasses, this tube also vented a small but steady amount of vaporized engine oil (which is normally abundant in the crankcase), which deposited itself as a thin oil film on the underside of the car.  This oil film was great at attracting dust and dirt, and making it stick to the car in a dirty, slimy, smelly, oily mess.   A similar thing happened in the engine compartment, because the oil filler tube had a vented cap to allow fresh air into the crankcase, to replace the nasty fumes coming out the road draft tube.  Well, this only worked when the car was moving, and there was enough air velocity under the car to suck the gasses out of the road draft tube.  If the car was stopped and idling, the gasses went up the oil filler cap and into the engine compartment.  Along with the oil vapor.  You can see where this is going... when I got the car in 1972, the entire engine compartment, and everything in it, was covered with a thick black fuzzy mixture of engine oil and road dust.  I steam-cleaned this gunk off, but I didn't get the gunk on the underside of the car.  This is why I thought the car stank.  I had to bathe twice to get the smell off me as a teenager.

Needless to say, I intend to convert the car to a Positive Crankcase Ventilation (PCV) system, which sends the crankcase gasses through a special valve and back into the carburetor or intake manifold.   It's OK to do this, since the gasses are mostly gasoline fumes anyway. This system has worked great since 1962, and cars have smelled remarkably better ever since!

One area that had a particularly nasty accumulation of oil-dirt-slime underneath the car was the differential.  This may be in part because the front seal may be leaking, slowly flinging gear oil back over the rest of the differential. Here's kind of what it looked like before I started cleaning.

I used a paint scraper to get most of it off in chunks.  Pretty nasty stuff, but the differential looks much better now.  You can seek some of the gunk on the ground.  The color in the picture is a little off... it's rusty, but not really orange.  I should probably remove the entire rear axle, and have Mr. Mechanic check out the seals.

Then it started to rain, so I decided to wash down the top of the car, take it down of the stands, and put it back in the garage.