How come sometimes you see the older Corvettes with hidden headlights where one is up (not hidden) and the other is down (hidden)…when parked. Someone told me there’s a vacuum system that holds them down (hidden), but the system can fail and defaults to the open (up, not hidden) position. This made sense at the time, but now that I think more about it, this does not totally make sense. If this is correct, how does a car create a vacuum when the engine is off? And, ultimately, how does this really work? …Springs? …Electromagnet?
Corvettes (and Firebirds) with pop up headlights, have a motor that raises and lowers the headlight door. These are a real pain in the ass when they go out. The headlight door can be raised and lowered manualy with a long allen wrench cranking it up and down by hand, which is also a pain, so sometimes people just leave them up awaiting repair.
These motors a really bad GM design and do not even have an adjustment to stop them and let the motor know when it is up. Instead the motor relies upon measuring the electrical resistance to tell it when to stop, there is a plastic gear inside the motor that gets stripped out and instead of registering resistance it just keeps grinding until it decides to stop. Because the lights activate and blink when you lock or unlock the car, the headlights will also grind each time.
No vacuum involved, just a motor with a plastic gear. You can repair the motor by replacing the plastic gear with a brass or aluminum gear but that can cause more damage when the motor goes out, or you just buy a new motor. If you want to replace the motor it is best to find a person with very thin hands and two or three wrist joints because space is very limited. I have replaced the motor on my Trans Am twice.
Seems to vary by generation:
When the 3rd generation Corvette debuted in 1968 it was an engineering marvel with its T tops, fiber optic light monitoring system, and vacuum-operated headlights and cowl. Pop open the hood and marvel at the labyrinth of color-coded hoses running throughout the engine compart and behind the front bumper.
As we’ve learned over years, these systems can be quite finicky as they age. We’re sure you’ve all seen Corvettes with one headlight (or both) open winking at you. If you’re C3 Corvette is one of those that need a little vacuum help, then our friends at Volunteer Vette have got you covered with their 1968 – 1982 Headlight Vacuum Kits.
No idea how it generated a vacuum, though it’s a good bet it reused the hardware for the power brakes.
My dad had an '84 Corvette, and each flip-up headlight had an electric motor, no vacuum required. If one of the motors died, you could open the hood and spin a little thumbwheel to deploy/retract the headlight. It was a pretty low gear ratio, so it took a while to hand-operate it; once you got the headlight manually popped up, you tended to leave it there until you fixed it.
FWIW, cars typically have a vacuum reservoir. I should say had, as I don’t know what the state of the art is these days. The vacuum reservoir assured that there was always vacuum available for power brakes and for moving HVAC dampers around, and the reservoir meant that vacuum continued to be available for some time after the engine was shut off. So in theory, it would have been possible to use vacuum as the power source for retracting headlights, but only until the vacuum in the reservoir was depleted. As @Dr.Strangelove’s link shows, there were indeed some that used a vacuum system.
Thanks, everyone! This is more an item of curiosity for me than trying to fix a problem. But, I enjoy reading the details. One more question along these lines: I understand a turbocharger relies on a vacuum system, or it did back in the 1980s? A radio talkshow on cars I’d listen to claims the vacuum on turbochargers usually gives out (due to leaks, I assume, thus losing vacuum) about 50K miles. Is this an accurate statement on the life of a turbocharger?
Turbochargers are driven by engine exhaust. That’s where the “turbo” in the name comes from. Exhaust gases drive a turbine, which is connected to a compressor to suck in air. It robs a bit of power from the engine since the engine has to work harder to expel the exhaust, but you gain power by being able to force more air (and more fuel) into the engine since you are no longer limited by atmospheric pressure on the air side of things.
Older turbochargers from the 1980s weren’t really up to modern standards as far as metal strength, bearings, etc. so 50k probably was a typical lifespan for one. Modern turbochargers are designed to last much longer than that, and are typically matched to the expected lifespan of the vehicle. So for a typical car, you’re talking 150k to 200k miles. The turbocharger on a heavy duty truck (like my F350) is built using much heavier parts and can easily last 500k miles or more.
The most common cause of turbocharger failure in a modern vehicle is a lubrication issue, either oil starvation (leak, blocked pipe, etc) or oil contamination.
A 1980s era turbocharger might have used vacuum for control, so yeah, if you have a vacuum leak then the turbocharger isn’t going to kick in. I wouldn’t call that a major failure though. Just fix the vacuum leak and it will work again. Bearing failures or cracked housings were more common failures back in the day (at least as far as I am aware). Like I said, the material science back then wasn’t anywhere near modern standards.
Some vehicles today still use vacuum controls. Others use electronic controls.
They still have them. They are still used for power brakes and they also control the turbo waste gate if the vehicle has a turbocharger and uses vacuum controls instead of an electronic solenoid to operate the waste gate.
In the old days, a lot of stuff was driven by vacuum, so you typically had vacuum ports coming off of the carburetor or throttle body, or sometimes they’d draw directly off of the intake manifold. These days, the vacuum reservoir is usually driven by a vacuum pump. Sometimes the pump is shaft driven and is integrated into the engine. Other times the vacuum pump is electrically driven and can be mounted pretty much anywhere inside the engine bay.
Fun fact: The 2004 Corvette was the last volume-production car to have pop-up headlights.