1970s A.I.R. Diverter Valve, 1978 Eldorado

[joeinbcs]

Howdy all,
I have temporary custody of a 1978 Eldorado Custom Biarritz Classic...a mouthful. I don't have any records, and, as the owner recently died, I have no way to ask questions.
I'm preparing the car for sale on Bring a Trailer as a charity auction to benefit Honest John's Texas Legends, a 501(c)3 charitable corporation set up to honor John Foust's memory by helping young victims of drunk drivers who have sustained severe traumatic brain injuries.
The car has 18K miles and hasn't been driven much in a few years, so running a little rough. I'll take it out for a Texas tuneup as soon as I replace the leaking master cylinder. But nosing around, I discovered that the vacuum line that should go from the A.I.R. Diverted Valve is disconnected and the fitting at the manifold is capped off.
Anybody know why this might have been done?
Thanks, Joe
And if you like these cars, it's a nice one. Should be live in a few weeks!

[TJ Hopland]

First thing to usually fail on these systems is the check valve which is that adapter dodad on the manifold crossover pipe that goes from the threads to the nipple.  Its a check valve to prevent exhaust from backflowing into the AIR system. These were somewhat universal so they should still be available today. Easy to check pull the hose/cap off and see if exhaust comes out with the engine running. 

When the valve fails the hot corrosive exhaust gets into the dirverter valve and kills it while also flowing all the way into the pump where it kills the bearings which then stop the pulley at which point you know there is a problem because you also loose the fan, waterpump, and alternator.  You then find out that apparently aftermarket never made the valve assemblies and GM hasn't made them for eons.

Pump is pumping air any time its turning.  Normal operation the air is being sent into the heads and injected just after the valves into the exhaust stream to do its magic. I think there are a few situations the air gets diverted to that little muffler thing on the valve assembly. The main one is deceleration. 

With a carb the mixture goes very rich when the throttle closes so a lot of unburnt fuel ends up in the exhaust.  IF the air is still being injected at this time at a minimum you get some popping and gurgling but if you are unlucky and maybe have other issues going on you can end up literally blowing  the muffler and exhaust system up and off the car. 

I don't remember what position the valve goes to with no vacuum signal.  I believe when they get burnt up they end up sending most of the air to the heads.

What happens when you cap it?  I guess you are breaking the law and have to check that box when you transfer the title that says the emissions system has been tampered with or modified but unlike cars with computers you don't end up with burnt exhaust valves and stuck rings from running lean and its less likely that your muffler is going to explode.   

[joeinbcs]

Thanks for that great explanation!
I think that's going to be something for the winner of the auction to deal with, or not. 
Once I get the brake master cylinder done, I'll be able to drive it more and do that Texas tuneup.  It seemed to run fine at speed, but idles irregularly.  I'll put some Seafood in the gas tank, as the gas is probably pretty old.  Hopefully that will get her running smoothly.
Thanks again!

[joeinbcs]

Just another quick question:  The driver side front turn signal is not working. When I took it apart, there was no bulb.  I have the correct bulbs, but can't figure out how to get the damn thing in.  I suppose that's why there was no bulb.  There must be some defect in the socket.  Do you know if the electrical connector in the back of the fixture just pulls off?  Any suggestions on how to fix this?  Thanks again!

["Cadillac Kid" Greg Surfas 15364]

Joe,
As long as it goes to someplace where there are no Emission testing requirements, a de activated AIR system should not do anything but mess up the carb calibration.
Greg Surfas

[joeinbcs]

Thanks, Greg.
What should I do about the front turn signal light bulb, which seems not to want to go in the socket?
Thanks, Joe

[TJ Hopland]

I don't think I have ever tried to take a socket apart before.  I would assume this is a dual filament bulb which has those side pegs at different heights to in theory only allow it to be installed in the correct orientation.  I wonder if maybe someone tried really hard to get one in the wrong direction?  Maybe look where the pegs engage and see if the metal is bent, maybe you can bend it back?

["Cadillac Kid" Greg Surfas 15364]

Joe
Do the contacts move in when you push on them?
Greg Surfas

[joeinbcs]

Finally go the bulb in and working.  Thanks, Greg!