Strangest car prep issue you've ever seen?

We have all come across things after taking over someone else's cars,projects or race cars. What is the strangest thing you had to figure out, what made you say WTF??

I was helping a friend prep his Turner for an event. It was the first time I had been in charge of a "Nut and Bolt" and fluids on this particular car, he had recently purchased it from out of state.

I pull the drain plug on the rear end and a watery green fluid pours out and then what looks like normal gear oil.

WTF?

I call the owner wondering if there is some new space age oil additive that I don't know about. He knows nothing about anything special in the car like that.

The head scratching begins. I get under the car to stare at the rear end to help me think. I notice a breather line coming off the top of the diff. I follow the line through the body to a roughly 2 quart container in the trunk. The hose is stuffed in there pretty tight. I notice there are a couple more hoses going to the container, all held snug in their holes.

I follow the other hoses to the front of the car. One is the the breather on the engine and the other is over flow on the RADIATOR!

It is a nice tidy install with bad engineering. We have no idea how long the coolant had been getting pushed into the rear end housing. It also explained the little droplets of oil in the coolant so I didn't freak out when I found those.

Wow.

When I bought my Turner, and still when I sold it 5 years later, the right front fiberglass fender was bonded together from the one of the original owner's crashes using an inner mold from a New Jersey license plate, the style that was discontinued in 1959. I don't know if it had been the plate on the car when it was new in '58. This car also had a handle on the passenger floor to use when ducking under the cowl during roll over. It had been used too. No roll bar then.

The number of wire nuts under the dash of my 57 Chevy was a little surprising. Not as surprising as the driveshaft yoke that had JB Weld holding it together. 

I bought my Neon race car as "race ready". Naturally I decided to give it a thorough once over before taking it to the track. First thing I did was jack up the front end and one of the wheel & hubs immediately fell off when I pulled on it to test the wheel bearings.

Also, one of the front brake pads was roughly the shape of a banana. 

When I bought my lil treasure, an awd mazda protege that had a 323gtr drivetrain swap, the first thing we noticed was the road noise I was warned about by the seller was a direct result of finger tight lug nuts. All of them. Once we got the car home, I spent a few days tightening every fastener I could get to. I bet 90% of them, from subframe bolts to shock tower bolts, motor mounts, geez I forget whatall, were loose. Like the seller had a torque wrench assiduously used but off on the low side by an order of magnitude. 

In reply to Jay_W :

If you don't know that units mean anything, in-lbs and ft-lbs are the same thing, right?

The brakes didn't feel good in my Silverado when I bought it. When I pulled the wheels I found no rear pads. Not wore out, just missing. There was a nail in the metal brake line to block it off. 

My 78 chevy pickup had no working dash lights. What I found was the previous owner had installed clearance lights on the roof. They cut the wire going from the headlamp switch to gauges and used that to power the clearance lights, which ran on a dimmer, and the gauges were no longer lit.

Not a car, but a boat. When we bought our first boat (we being my family, I was 10), it needed a lot of work. One interesting thing that we found was, for some unknown reason, the PO had swapped the bilge and the horn switches. Flip a switch and the horn would blow until you flipped it back. Get water in the boat? Push the horn button and hold it down until the water is gone. 

I'm assuming it was not intentional. 

I posted about this in the thread for my YJ "Wrongler" but it fits well here...

The power steering leak seemed to be coming from the low pressure return hose.  So I bought some hose to replace it.  When I went to pull the old hose out, the inlet tube came out of the pump and stayed in the hose.  Hmmm...so I looked a little closer:

Someone spent valuable time grinding down this 3/8 drive, 7/16" deep socket, jammed it into where the broken-off old inlet tube still was, clamped the return hose on the other end, and nodded with pride while whispering "send it" to himself.

So a few years ago I bought what was probably the cheapest running and driving (both words used loosely) 944 turbo in the country. One of its many issues was the brakes basically didn't work. Upon investigation, I discovered that somebody had put the wrong rotors on the front, presumably something they had laying around or found cheap from an older 911 or something. The distance from the hub surface to the outer pad surface was about right, but everything else about it was wrong. The OD was a little bit small and the rotor was waaaay too thin. This is the only photo I have of the situation as I got it:

So you can see that the pads had worn down with a big lip where the outer edge of the pad was riding on air instead of rotor. But what's less obvious is that the rotor being too thin had at some point resulted in the inner pistons over extending and seizing and also probably introducing some air into the system. So the front brakes basically didn't work and the car was stopping with just the rears...which also had some air in the lines. Happily included with the car was a brand new set of rotors and pads and some freshly rebuilt calipers.

The brake stories scare me the most.

I remember as a kid we had a German car specialist mechanic within biking distance of my house. I used to stop in fill my bike tires and see what they were working on.

One day they had late 60's Benz that had little carbon chunks coming out of the exhaust every once in a while. The car's owner had noticed them on his driveway and brought the car in.

Rev the car and you had a good chance of getting a prize out of the exhaust. Little 1/4"ish chunks of carbon.

Worst case scenarios were all considered of course.  The second in command mechanic hits the muffler and you can hear chunks rattling around inside.

He starts to dig deeper into the engine to give the owner some solid bad news. The first thing to come off the car is the air filter canister.  He pulls it open and finds dog food around the filter. There is a hole chewed through the filter that allows anything to pass through into the intake tract.

Rats or squirrels had been stocking up for the winter and the little Benz had been eating their stashed food.