Question on how the lever air pump system is to work correctly on my 74 Eldorado

[collector]

I bought a set of NOS GM original rear air shocks (the ones with the one port on one side and the double port on the other) I just put on my NOS vacuum pump and it keeps pumping. The air gauge only goes up to 125 psi so I cant tell how much is actually in the system. The car is very level and it will not raise any higher shouldn't it stop pumping? I even took a compressor and tried to fill the tank but its full. I waited about and hour and still no air has escaped the pump or the system. I thought after the pump reached its full potential of air it would stop pumping. Shouldn't it? It isn't loosing any air and I let it run for about 15 minutes at idle. Just wondering if that is how the system works. I wonder if I have the vacuum lines coming from the engine on the wrong port. I have the main vacuum line going to the top port and the air from the breather going to the side port. I'm thinking that is how I remember it was from before. The system hasn't worked in about a year since the pump went out. Now that I have the system up and running correctly I'm wondering why it keeps pumping even if it isn't leaking or if that is just how the system works. Since I can not find my shop manual I'm going to have to go by someone who has one of these systems and knows how they work. Please advise. Thanks, John

[collector]

Never mind. I must not have let the car run long enough. The pump started slowing down and finally stopped. I turned the car off waited a hour restarted the car and the pump didn't cut on again. I guess if I get in the car it will load down on the level and pump until the car levels out again. Man its wonderful to have a complete NOS working system. This time I'm putting on in line charcoal filters so that gases from the manifold and the air cleaner do not bleed back into the system, which I found out what gummed up my original pump. It had so much varnish and goo that I figured out that is what kills them. I also opened up the tank and sprayed the inside with rust proofing so that the metal doesn't corrode. I noticed the inside looked like (on the original one) that moisture had entered into the unit causing damage to the valve and rust inside the tank part. This way I will have covered all base's. I also sprayed a protective lubricant over the entire inside of the case and the inside of the unit so in case moisture/condensation gets in, it will not be able to attach the parts and cause any deterioration. Thanks again, John

[Glen]

On the compressor the side port is the vacuum port and should be connected to a vacuum source.  This hose is teed off from the PCV hose on the ’68 â€" ’70 Eldos.  I’m not sure if that is correct for your car. 

The port on the end is the air port and should be connected to the fitting on the top of the air cleaner. 

This compressor will run for a long time if starting from empty.  The compressor fills the reservoir until it stalls, meaning the vacuum on the diaphragm is not strong enough to push more air into the reservoir.  This happens at about 280 PSI. 

On the side (or top depending on the way your compressor is mounted) is a regulator with a yellow cap.  That regulator sets the pressure in the hose to the rear at about 125 PSI. 

So you can see the compressor will run for a while after the shocks are inflated to the correct height. 

[collector]

The compressors are the exact same, the difference is only in the length of the reservoir and location of the mounting. So, I guess I have them backwards. Ill change them around but for some reason it still works. Ill see if changing them makes any difference. I did notice that after about 8 hours the car did drop a little about 1/8 of an inch. I wonder where the leak is or is it normal? I did notice it makes my idle rough where as it ran much smoother when I had it plugged off. I think I might have to richen the idle a little to compensate. I would actually love to change the carb to a Carter AFB. That way I can adjust the air and the fuel. I wonder if it will fit and the breather will work. I know its not original but I know I can get a much better idle and they are a much better carb all the way around. I actually have never had a Cadillac with the Rochester carb run well. Only my cars with the AFB's run like silk. Im also told that the 472 and 500 engines never ran smooth. Truth or fiction? I know from experience I havent had one Cadillac with a Rochester run smooth.  Question Carb or engine?

[collector]

Update, found vacuum line off of breather, took care of rough idle but still not flawless. Yes, your right I was mistaken I already had the vacuum lines as you described. Thanks Glen

[TJ Hopland]

125 psi should be in the ballpark of getting a typical eldo close to level. 

[collector]

FYI  Glen is a very wise and knowledgeable man. He helped me solve the problem. I waisted a little money and some time but all in all found out that the slight leak was due to  the rubber inside the brass fitting on the level assembly, which was totally disintegrated, leaving a huge leak. After I spent a bit of time putting in NOS lines from the compressor to the level assembly, I removed the fitting from the level assembly and the rubber just fell out in crumbs. I had to remove the rest with a very fine pick. After I closed the system and filled it with air, I let the pump do its job. The pump finally stopped pumping and now the system is air tight. I went out about 5 hours later started the car and the pump didn't pump at all. Man if only I had checked the fitting first, I would have saved myself a lot of headaches. I even bought an NOS level assembly which will be here on Tues., that I don't actually need. I guess I'll put it on Ebay to get my money back. Thanks guys for all your advise and help. I could kick myself sometimes.

[Glen]

Thanks for the kind words.  I’m glad I could be of some help and that you got that nice looking car fixed. 

[R Schroeder]

That is one nice looking Caddy. Love the color.

What surprises me is the amount of pressure in these systems, on the 74.
I have level ride on my 78 DeVille ,but it only takes 25 to 30 pounds to level it off.
125 pounds would extend the stock straight out............ha

Is this an air bag type system, or is it a air shock ?

Roy

[Rob Troxel]

Collector,

Let me know is you wish to sell the level assembly you just got.

Regards,

robtroxelemail addresses not permitted

[Glen]

What surprises me is the amount of pressure in these systems, on the 74.
I have level ride on my 78 DeVille ,but it only takes 25 to 30 pounds to level it off.
125 pounds would extend the stock straight out............ha

Roy

The max pressure in the reservoir on the vacuum operated system is around 280 PSI.  There is a regulator that drops that to 125 PSI, but that only goes as far as the control valve at the rear axle.  Beyond that the pressure is only as much as needed to bring the rear bumper to the correct height.  125 PSI is the max pressure that the shocks are designed for.   So that would only happen if there was a load greater than the system was capable of  compensating for. 

[R Schroeder]

OK, I see now. Mine just pumps what is needed to raise or lower it.
It is controlled electrically. Yours has the pressure lines being controlled.

[marc]

I would also be interested in that level asse,Bly or at least find out where you got it.

[collector]

It is an NOS one and I it was the only one I found. Ill email you with a PM