1970s Replacement Shocks for ALS '72 Eldorado

[72EldoRagtop]

With me, and 1 passenger in the front, nothing (no spare) in the trunk but a sub woofer and a couple amps. And up to 12 gallons of gas...

72 Eldo Convertible. Ride is extremely smooth with about 32/30 PSI.

I mostly drive it on winding country roads, up to 45MPH; but I occasionally  get on the highway and go 70MPH for an hour or so.




Put about 20 gallons in the tank: Starts to sag in the rear, and bottoms out on the hill in my driveway. This also happens with passengers in the back seat.

I know the ALS compressor is not connected to anything. So I'm guessing that the stock rear air shocks are out of air.



I would like to first Find a way to inflate the shocks to see if they hold air. How would accomplish this?

Then if they are NOT holding air, do I replace them with Monroe Air Shocks, or, do I go with the KYB gas-a-just - and no longer deal with the ALS system ??


Odometer just hit 48K. It's a #2. So I don't mind scrapping the old system. I'm just concerned with a comfortable ride, and no bottoming out with or without weight in the rear.

I used to drive a '65 Electra convertible. The ride OF the Caddy seems even more floaty than that boat. So tightening up the suspension a bit won't bother me either.

Thanks in advance for the advice

[TJ Hopland]

The rear springs when new were a little on the weak side because they were counting on the air to do the rest of the work.   The FWD Eldo's the air was standard so there was never a listing for a standard spring. 

If you have no idea how old they are very little chance they would hold are and also a good chance they are not doing much damping.   I have a theory that no one has made new air shocks for these cars in a long time and we have been working off of old stock for a while now.  Seems like every few years I have one leaking oil.  I used to replace them in pairs but quit doing that and just replace the bad one now and that has been working out and ever one I have bought in recent years no matter the name on the box has been the same except for the paint. 

You can buy the air hose kit separately for $10-20.  If its still got factory shocks the fittings are different and its possible older aftermarket ones used different fittings too but the OD of the line is usually the same so you can splice onto the lines.   Kits don't usually come with the splices and the factory one shock had 2 ports so the feed went in then another hose went to the other shock.   A good hardware store will have the fittings but be prepared to be shocked how much they cost if all they have is the brass ones.  That size isn't used in regular plumbing so not many stores stock that small size.

Basically I'm saying I would just go buy the new set that in most cases comes with the lines and install them and be done with it. 

I don't think I have owned a car with a working system, mine have always been manual fill and I have usually found a setting that works reasonably well for most uses but a full tank plus your sub plus rear seat passengers could require a little more air unless you don't mind it running a bit high when its empty.

The factory vacuum powered compressor worked kinda like the compressor you would have in your shop.  It had a tank and would just work to maintain tank pressure.  The valve back over the rear axle was where the 'brains' were.  That valve has 3 ports, one is the supply from the compressor so in theory a steady pressure.  There was then the line to the shocks and the 3rd was a vent port.   Depending on the height of the axle what it did.  In the neutral position all ports were closed. IF the rear dropped it would connect the compressor port to the shocks so the car would raise and close the port.   IF the rear was too high it would connect the shocks to the vent and the car would lower.  There was some sort of internal damping mechanism plus the size if the ports that kept the system from responding too quick like when you went over bumps.

So if that rear valve is still in good working order in theory you could get a 12v compressor with a tank and auto shut off and other than the occasional noise it would work like factory.  If you got amps you already got power back there.  If that valve is messed up then you could set something up like the electric factory pumps where the pump ran to inflate them and had a dump valve (on the compressor) if they needed to go down.  Factory used a not very reliable control module sensor unit for that but you could rig up some sort of switch.   

[72EldoRagtop]

"Basically I'm saying I would just go buy the new set that in most cases comes with the lines and install them and be done with it. "


Thanks for the detailed response. I'm leaning toward following your advice for the next step. Rock auto has the Monroe MA 751 for $65/pair. And I should also order the Monroe AK18 Air Shock Single Fill Kit for a few bucks more...

I'll start with that. Not exactly sure how I'm going to be able to access a Schrader valve in order to adjust the height in the rear.
How is that done?

Here's a pic of the kit:

[72EldoRagtop]

And, to be clear, you do not advise switching to the

KYB KG5507 Gas-A-Just Monotube...?

[The Tassie Devil(le)]

G'day Bill,

I hear your concerns.

Firstly, there is a pressurising schraeder valve at the ALC pump where you can inflate the system with the hood up.   If it won't raise the rear, then you have a bad shocker at the rear, or a leaking line, or other problem.

The Pump-up Monroes don't look like the one you pictured, but a lot fatter, with a rubber insert.   This is the one.  MONROE MA751 Max-Air Shock Absorber; Sold In Pairs

I placed my filling point at the back of the frame, behind the left side rear bumper.

I will take a picture of it shortly.

Bruce.

[TJ Hopland]

I tried those gas adjust things on a car one time and they didn't seem to do anything different than a regular shock.  I think I was told that they only work with their variable springs which I then got for the car and that made things worse so I think I ended up putting the original springs back in that car. 

They give you enough hose in those line sets that you have options where you mount it.  On my 73 its on the bottom of the trailer hitch.  Other cars I have been able to drill a hole or make a little bracket that attaches to an existing screw near the gas filler so its then normally covered by the gas door or licence plate in this case. 


With the original compressors I thought bad things could happen putting air in that valve on the compressor?  Seems like I once suggested that and got chewed out for suggesting something that was sure to cause the world to end as we knew it.   

[The Tassie Devil(le)]

That is why the Schraeder Valve is on the Compressor.   The Factory calls this valve a Service Valve.   It is mentioned in the Shop Manual - 16. Regulator Test.

Here is the Valve on mine, right next to the Left Rear Bumper Bar mounting.   Now, looking closely at the last picture, it shows the T Junction of the lines, plus I also see another task that I have to do.   The Body Mount above the chassis corner is totally shot.   Now to find some new rubbers, and pull the body from the chassis, and replace the lot.   All that "Greyness" under the car is road grime.

Bruce.

[72EldoRagtop]

Wow. over 26K posts between you 2 guys.
Thanks for the expert advice.

I'm gonna take this step by step and try to avoid any confusion or foulups.

1. Find the service valve on the compressor (I have a service manual to help me) - can I not just attach a tire pressure gauge on this to measure PSI?

I'm guessing it's going to be close to ZERO.

2. Connect a compressor to the service valve and see if the rear comes up, and if it holds. -Can I not simply use a bicycle tire pump? I mean the system is supposed to hold b/w 20 and 150 PSI, and it is very low volume... But if not I can use my electric pump.

3. If it does not hold pressure, find the leak. Usually in the shocks themselves? Would I hear the hiss?

4. Replace shocks if necessary, and might bas well replace the old lines and rig a schraeder valve to the gas cap.  Sound about right?


PS. I just bought this car last Feb. PO focused on only a new super-duper sound system. So the amps and sub in the trunk were included. I have since removed all the audio stuff in the cockpit that didn't look original. Now using a head unit that "looks" original from Classicaudio - loosk like an AM radio, even says "Cadillac" on it.
 

[The Tassie Devil(le)]

The factory pump can build up pressures from a low at 150 psi to 275 psi.   Which is some serious air pressure.   It also says that the output pressure of the Regulator to the Shocks is 125 psi.

When I am pumping up my Monroes from Rock Auto, I don't go any higher than 70 to 80 psi.

I have an electric (12V) Monroe Max Air Compressor that I haven't decided on using as yet, as I still want to get my original working.   It pumps, but I need the special "ring" for it.

Bruce.

[TJ Hopland]

I generally run mine at around 125 which is what my shop compressor tops out at.  With less gas in the tank and no one in the car it sits slightly high but a full tank gets it closer to level.

[72EldoRagtop]

Thanks for your help on this ALS stuff. The service manual helps, but of course it doesn't mention replacing the system 50 years in the future.

New Monroe shocks have one vale each to fill/release air.
Original pair of shocks, LEFT one has one valve, RIGHT one has two valves - where the second valve on the RIGHT connects to the LEFT's only valve - and this is to equalize pressure on both sides.

So when installing the replacements, should I go with a "T" and just have one valve that will send equal pressure to each shock; or set up 2 separate valves, one for each shock?

[Roger Zimmermann]

A "T" and only one valve. I'm using this set-up on my two older cars.

[72EldoRagtop]

Cool, Switzerland, Australia and Minny... I'm here in Mass.

I imagine the PSI is all different in a Coupe DeVille - with rear-wheel-drive.

But I'm curious, at what ## do you keep the PSI ?

In the FSM, figure 4-16 shows me the fitting on the end of the tube. Calling it a "Metal Sleeve and Rubber Seal Assembly".

So that assembly is included with the Monroe Air Shocks from R.A., and I do NOT need to buy the kit?

Thanks,
Bill

[TJ Hopland]

Ya the last many years it seems like you get the hose and T kit with the pair of shocks.  I do remember a time where they were they didn't come with and you had to buy them separately.  I seem to remember at one time there was a different hose kit if you were hooking to a factory system so that could be why they didn't include one with the shocks.

[72EldoRagtop]

Okay thanks you guys. I ordered the parts. I'll keep you posted I mean I'll keep this thread posted on what happens next. After I jack up the rear end start pumping air into the system etc. Should be an adventure. An adventure into the unknown (for me).