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
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.
"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:(https://www.rockauto.com/info/904/BCZC_AK18_P04_FRO.jpg)
And, to be clear, you do not advise switching to the
KYB KG5507 Gas-A-Just Monotube...?
(https://www.rockauto.com/info/63/KG5507.jpg)
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. >:D
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.
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. >:D
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 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. >:D
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.
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?
(https://www.rockauto.com/info/904/BCZC_MA751_P04_FRO.jpg)
A "T" and only one valve. I'm using this set-up on my two older cars.
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
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.
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).
Job went smoothly with one monir hitch:
I notice that the new shocks were about 2" shorter than the originals.
Connected the uppers to the body first.
Then, in order to connect the lowers, I had to jack the axle up (about 2"inches).
Installed all the airlines and Schrader valve.
Now- go to put the tires back on , and there's not enough clearance in the wheel well.
The workaround was to deflate the tires.
Didn't pump up the shocks until the tires were back on. Then put in 80PSI.
I couldn't be more pleased with car's posture. Looks muscular and healthy now with the rear end up and not dragging ass.
Would putting air in the shocks allowed them to lengthen any more, enough for clearance for tires to go back on?
Anybody else experience this tire space issue?
Tires are Starfire SF340...
P235/75R15.
Original rims.
The shocks will only expand to their physical limitations.
Hypothetically, what are you going to do when you get a rear flat on the road? Deflate the spare to get it on? Now you need to get a small compressor. This will allow you to refill the spare and pump up the shocks when you load up the trunk or put a crew in the back seat.
Quote from: Big Fins on July 21, 2025, 12:05:47 PMThe shocks will only expand to their physical limitations.
Hypothetically, what are you going to do when you get a rear flat on the road? Deflate the spare to get it on? Now you need to get a small compressor. This will allow you to refill the spare and pump up the shocks when you load up the trunk or put a crew in the back seat.
I understand that the length of shocks are limiting the space to install the tires.
I was just wondering it was normal, after installing these new Monrow Airshocks, to have this issue - or is it me? Or, would inflating them first have somehow increased the length by an inch or 2, and now allowing clearance for the tires.
I carry a compressor that runs on DC12V or AC.
I don't carry a spare. I have roadside assistance. Do all you guys still carry a spare and the original jack, etc. and rely on that?
I suppose if you were planning a trip across a desert, or a long stretch of rural miles with 10X of miles between exits?
I am running the same rear pump-up shocks, and don't have any problems removing and replacing the rear tyres. But, you have to use the original Bumper Jack to get the side of the car high enough on that side, which at the same time, drops the other side down low enough to lift the wheel high enough into the fender.
This movement of the rear axle allows for the wheel being changed to drop down sufficiently to get it off and back on.
Bruce. >:D
I believe the 235 tires are slightly wider than the originals but I would not think enough that they would not fit at all. You had it jacked up by the frame (or bumper) or under the axle? If the axle I could see it being tight but since the shock wasn't extended at that point should not have changed with the new shocks. By the frame I would think there should be a bunch of clearance. Hate to ask a dumb question but I assume you removed the skirts?
Quote from: TJ Hopland on July 21, 2025, 08:46:06 PMHate to ask a dumb question but I assume you removed the skirts?
LOL
One side at a time. why didn't i think of that ?!?
Yes, jack was on the middle of the axle.
Makes sense now.
Anyways. Thanks you guys.
It's ridin' high now.
And i can finnaly fill the tank - all 27 gallons.
Which should get me about, what,250 miles?
91 octane...
Quote from: TJ Hopland on July 21, 2025, 08:46:06 PMI believe the 235 tires are slightly wider than the originals
Now I'll have to go and look up the stock tire size...
If not P235 75, then, What?
I am running 235 x 75R x 15 by Maxxis under my '72, and no problems.
The next size down is 225, but these will change the rolling circumference.
Bruce. >:D
PS. It will be impossible to remove the tyres and wheels if the car is lifted by the centre of the axle, even if the tyres are deflated.
PPS. I carry a small 12 Volt Compressor as I have a Space-saver as my Spare on the Continental Kit.
Quote from: The Tassie Devil(le) on July 22, 2025, 12:46:33 AMI am running 235 x 75R x 15 by Maxxis under my '72, and no problems.
The next size down is 225, but these will change the rolling circumference.
Bruce. >:D
PS. It will be impossible to remove the tyres and wheels if the car is lifted by the centre of the axle, even if the tyres are deflated.
PPS. I carry a small 12 Volt Compressor as I have a Space-saver as my Spare on the Continental Kit.
The lift was removed from the center axle, and sitting on the jack stands. Jack stands were placed on the frame rail - just forward of the rear wheels.
Is the conclusion/solution to remove the jack stands, and then jack just one side of the car?
Quote from: 72EldoRagtop on July 22, 2025, 05:45:46 PMThe lift was removed from the center axle, and sitting on the jack stands. Jack stands were placed on the frame rail - just forward of the rear wheels.
Is the conclusion/solution to remove the jack stands, and then jack just one side of the car?
Yes. You have to only jack up one side of the car, allowing that side of the rear end to sag to the extent of the Shocker. The opposite side is pressed up into the body.
This "angling" of the axle allows the wheel to be removed whilst fully inflated.
The cars were designed for the Bumper Jack, and if properly placed, according to the Owners Manual, there will be no damage to the bumper bar. What i do is to slightly angle the upright of the jack to the rear at the high point. This way, as the car lifts up, the jack shaft will move towards the vertical.
It is imperative that you chock the diagonally opposite wheel to stop any possibility of vehicle movement. If the Factory chock has been lost, any rock will do.
Pictured is mine jacked up showing no distortion of the Bumper Bar. Sorry about the poor quality of the picture, and the unfinished Continental Kit, but I weas in the process of constructing the kit. Plus, I used the piece of wool to protect the chrome. That piece of wool is a pocket that my loving wife made for me to hold the small jacking pieces when sitting inside the trunk. One day, when I have my next flat tyre, I will take a better picture.
Bruce. >:D
Quote from: 72EldoRagtop on July 21, 2025, 11:48:55 PMNow I'll have to go and look up the stock tire size... If not P235 75, then, What?
I believe 71-74 stock tire was L78-15. There isn't a perfect cross to the metric sizing that we started using in the mid 70's.
Diameter in inches:
L78 29.3
235 28.88
225 28.29
Width in inches:
L78 8.85
235 9.25
225 8.8
So the 235 is roughly 1/2" wider and 1/2" smaller diameter. With the 225's being an inch smaller diameter the speedometer will read 1 MPH higher than actual at 55 so really not a big deal.
I have usually ended up with 225's. I had one eldo that had a rubbing issue and a later non removable skirt car that was a tight squeeze on the rear. At times the 225 was easier to find with a white wall since that was more of a 'car' tire and the 235's tended to be 'truck' tires with the white letters but 15" truck and car tires ended in the earlier 90's so 30 years later its a whole different game that seems to change every time you look for new tires.
Quote from: The Tassie Devil(le) on July 22, 2025, 09:17:46 PMYes. You have to only jack up one side of the car, allowing that side of the rear end to sag to the extent of the Shocker. The opposite side is pressed up into the body.
This "angling" of the axle allows the wheel to be removed whilst fully inflated.
The cars were designed for the Bumper Jack, and if properly placed, according to the Owners Manual, there will be no damage to the bumper bar. What i do is to slightly angle the upright of the jack to the rear at the high point. This way, as the car lifts up, the jack shaft will move towards the vertical.
It is imperative that you chock the diagonally opposite wheel to stop any possibility of vehicle movement. If the Factory chock has been lost, any rock will do.
Pictured is mine jacked up showing no distortion of the Bumper Bar. Sorry about the poor quality of the picture, and the unfinished Continental Kit, but I weas in the process of constructing the kit. Plus, I used the piece of wool to protect the chrome. That piece of wool is a pocket that my loving wife made for me to hold the small jacking pieces when sitting inside the trunk. One day, when I have my next flat tyre, I will take a better picture.
Bruce. >:D
Thanks, Knowing that things work correctly as long as you lift the car correctly - is very helpful. But I'm sure my mechanic is going to scratch his head when I try to explain this to him...
Because, according to him, the limitation is the length of the shock. So how would putting the jack on the bumper on one side, allow the shock to lengthen another 1"-2"??
Bought this 72 Eldo last January. No spare. and No JACK included.
Have any ideas how to get enough clearance in the wheel well - using a hydrolic floor jack? Where to place the lift arm?
Quote from: TJ Hopland on July 23, 2025, 12:30:05 PMSo the 235 is roughly 1/2" wider and 1/2" smaller diameter. With the 225's being an inch smaller diameter the speedometer will read 1 MPH higher than actual at 55 so really not a big deal.
Thanks. The other option; get new 225's.
Maybe next time. Car came with 4 NEW 235s. (No spare)
Place the floor jack right in front of the rear wheel to be worked on. Be sure it's on the frame rail.
It will lift it the same height as the bumper jack.
If you are lifting or supporting the car from the axle the weight of the car is basically the same as if the wheels are on the ground so the shocks are compressed and no where near their fully extended limits.
IF you jack the car from anywhere else the axle will hang down to the point where the shocks are the limiting factor and then yes in your case 2" less than before but this should be many inches lower than ride height so plenty of clearance to get the wheels out with the skirts off.
Finding a good way to jack these cars up road side is tricky because of things like the rear clearance. Can't jack from the axle for the reasons you note. If you try to jack from the frame between the frame flex and how far the suspension has to sag you need a lot of travel in the jack and you can't get that out of a bottle jack unless its a 2 stage telescoping one. I'm carrying a jack out of I think an 80's car which is sort of a scissors design but instead of a screw it uses the ratchet track sort of thing like the bumper jacks used so its got a decent amount of travel. The 80's cars had a little pocket in the frame that these jacks fit into.
Quote from: 72EldoRagtop on July 23, 2025, 04:29:01 PMThanks, Knowing that things work correctly as long as you lift the car correctly - is very helpful. But I'm sure my mechanic is going to scratch his head when I try to explain this to him...
There is worse left to come. Try taking an Eldorado wheel with tyre to a tyre shop for a replacement tyre.
The "tyre Fitter" will in most cases give up because they cannot get the tyre from the rim.
These tyres have to be removed when the rim is placed backwards on the tyre removing machine. Just like the 1957 Chevrolets.
I was able to supply a fellow Eldorado Owner with 4 replacement rims after the originals were bent out of shape by a stupid tyre fitter.
I had a similar thing happen to me in Connecticut, but happily, they stopped before destroying the rim. When I came back to the shop, they explained that they couldn't fit my new tyres, as they couldn't get the old tyres off. So I showed them how to do it. The hardest part was getting permission to go behind the barrier and into their work-space to operate their tools. Once in, it was a learning session for the employees.
Bruce. >:D
You aren't the only one to do that. For that same reason, I had to buy an entire set of rims.
How are the new shocks working out shock damping wise? I leaned on the rear of my car yesterday and it didn't seem like there was a lot of damping going on. I wasn't curious enough to lay on the ground and look to see if there were signs of oil leakage. Its also possible I just have not leaned on an old soft car for a while, only more modern stiff stuff.
So, The car rides beautifully with the new shocks. The old ones may have been dampening but they were 100% deflated. So with a person in the back seat, and/ or 1/2 tank of fuel it was hanging low. Not a good look at all. And it would bottom out on the bottom of my driveway - I think that was probably a little scrape of the chrome-tipped, downturned tip of the tailpipe. Very unsettling. Embarrassing. I once had to ask coupe people to not get in the back until the car was out of the driveway and on the road.
It would also bottom out going over certain bums, speed bumps, etc. with passengers in the backseat. Found out that is was the muffler when I was under the car. Lucky I didn't ruin my exhaust.
The ride is a lot tighter on the highway. But still a very smooth and normally floaty '72 Eldo ride. I run the tires at 30PSI front and back. And I know tire PSI is a hot debate. So I'm still experimenting.
As for pushing down on the rear quarters, I'm 180 lbs. With nearly all my weight i can depress it a few inches. Then it comes right back up, then back down about 1" to it's resting level with 80PSI in them. And I put 20 gallons of fuel in the tank. 1/2 & 1/2 Hi-test/Regular.
Thanks for all of you guys on here. Really helped giving me the confidence do it in my driveway, using the right parts, and getting everything right. LOL... The tire not going back on was a headscratcher. First I was like: NO FN Way. I need to put the tires on BEFORE the shocks? Then it occurred to me to deflate the tires. And of course now I know to jack one side at a time.
Next 2 big jobs on this car are
1. Heater Core (it was disconnected when I bought it so I'll test it - but I'm not expecting it to be working.)
2. A/C. It has factory A/C but the lines going to the rear of the compressor have been disconnected.
I remember reading somewhere that the A/C will not work if the heater is not working (?).
Any way I'll start a new thread. And I'll start out asking for opinions on a quality heater core the $36 or the $86 or in between.
So when you push it down and let go you get like a single half a bounce? I feel like that would be normal. I feel like I'm getting more like a 2nd full bounce then maybe the 3rd seems to dampen.
More like just one tiny bounce.
I remember hearing once that when you see a car on the highway at 60mph+
And looking at the tire/wheel straight on from the side... A bad shock will
cause the tire/wheel to rapidly jump up and down, though the driver/passengers
may not notice it at all. I've seen it.
Is this accurate?
True?
I have seen it and witnessed it personally.
I was driving my 1959 Ford Ranch Wagon on a rough dirt road, and nothing out of the ordinary.
But, when hitting the sealed surface, my wagon was all over the place. I stopped, and one of the rear tyres was totally shredded.
The thing about front and rear suspensions is that the front going bad, the driver immediately feels it as the steering wheel id directly connected to the wheels, whereas the rear wheels are totally isolated.
I also had a rear tyre delaminating on my Eldorado, and only felt it when I heard the rubber strip hitting the inner fender. Pictured is the bad tyre, and the witness mark caused by the loose flap, well after the start of the tread separation. (Plus, I had 3 passengers in the back, and the top down.) Whereas when the front tyre started to tread separate, I immediately felt it.
Bruce. >:D