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Magnetic Ride Control

Johnscsx

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I just replaced all four magnetic shocks at about 80k miles. However, the car is used and I have a poor history on it. I do have a dealer record to indicate the right front strut was already replaced at 58k miles, and I strongly suspect both the rear shocks were replaced at some point very early in the car's history, due to wrench slip marks on the top rear mounts.

Like I said, I bought the car used at about 80k miles. I took it to a mechanic for a checkout, and he said one of the rear shocks was leaking. I went under there, and sure enough it was true. So, I replaced both rear shocks. I think I paid about $350 each, or something like that from rock auto. Install was easy enough. There is a tricky air tube to detach, but not a big deal. Also, the electrical feed goes in through the top, and you have to take out the trunk liner to get at it. Really though, not hard to replace the rear shocks, just expensive.

(Side note on the leaky strut issue: GM issued a TSB on this, as they seemed to think the dealers were replacing too many leaky shocks. They actually went so far as to say that some leakage is OK, just as long as it is not running all the way down the side.)

About a month later I started hearing a squishy sound from the left front whenever I would go over even a small bump. I didn't know if it was the shock, or a worn bushing, or what. So, I replaced both front struts. Those are a little more expensive than the back, and a whole lot more work to replace because of the mcpherson spring that must be compressed. Fairly straight forward replacement procedure though. The wires for the struts plug into the bottom of the front struts.

Strangely enough, the mount for the right front strut that had been dealer replaced at 58k miles was broken. (center mounting rubber ball at the top of the strut assembly torn out, but the overall strut was still resting on the bearing OK.) Also, the same shock didn't have as much pressure in it as the new one on the other side did, which caused the car to sag on the passenger side by about 1/2" or so until I could replace both sides. This caused the car to bottom out just pulling out of my driveway, and it is not even a significant bump. Putting the new shock in there fixed that, and gave the front end on that side more lift. This is a very low riding car by design, and you just can't afford to let those shocks wear out.

Ater removal, it was obvious the right front shock was definitely shot, and was probably original equipment. I say that because it was made by Delphi, and Delphi hasn't made any shocks since the GM bankruptcy. The replacement ACDelco shocks are now made by a company call BWI (did I get that right?), and the "B" stands for Beijing, as in China. However the BWI shocks are actually manufactured in Mexico now. So, if you don't have any maintenance records you can get a rough idea how old your shocks are just by looking to see if they are Delphi or BWI. If they are Delphi, they are probably original equipment.

I think I paid about $50 for the new strut mount, which I found locally at O'Rileys. (Advance and Autozone couldn't help me).

If I had to do it again I would have replaced the strut mount for both front sides, not just the broken one. I'm not sure how long the original one is going to last. Also, the original bearing was open when I took it off, with the metal bearing balls exposed. I just put some lithium grease in there and put the whole thing back together. However the new strut mount I bought for the other side had a sealed bearing unit which made assembly much easier. This causes me to wonder if the original bearing was also sealed at the factory, and it just broke open somewhere along the way? I'm not sure, but I think it is good practice to just replace the strut mount and bearing whenever you replace a strut. It's too much work to take those things apart. The springs on my 07 Lucerne CXS are very small, and the spring only gives you two loops worth of metal to compress, so you have to compress those two loops all the way to get the top of the strut off.

So what was wrong with the noisy original shock? After I took it off it seemed obvious that a seal had broken somewhere, and a lot of air got in there, rendering the thing virtually useless. (no oil leakage that I could see) I didn't notice the broken shock because it probably happened over a long time, and/or the active magnetic system probably somewhat compensated for the loss of pressure by tightening it up as necessary. (the magnetic system can't however increase the strut's lift, only tighten up the travel. The back struts however can be raised and lowered by the compressor.) The only reason I replaced the left front strut was because it was making noise, and it was only after replacing it that I noticed the car rode a little higher, and no longer bottomed out in our driveway.

So now back to the original question, how long do these magnetic shocks last? I suppose a lot has to do with the climate, and how many bumps they are exposed to, and the severity of those bumps. I saw something somewhere from AC Delco which says they're good for 50k miles, but you sure don't see anything like that in the owner's manual! This specific car was previously driven in Florida, where they generally have NICE SMOOTH roads, so that probably helped extend the life a bit. On the other hand the awful heat there is probably not good for anything mechanical, though it probably beats the abuse in northern climates from cold, ice, and road salt. So, I think I'll stick with AC Delco's 50k mile replacement suggestion.

My advice is do it yourself, if you can. I've seen comments on forums which suggest that dealers can charge north of $5,000 to replace all four of these things, but you should be able to do it yourself for under $1700 if you shop around for the best prices. (dealer labor rates seem to vary based on what part of the country the dealership resides in.)

One other option is to install regular shocks on your CXS. This is tricky though, because the suspension computer is expecting to see those magnetic shocks working. There is a company on the internet that specializes in this, just google it if you are interested. They send you a set of regular shocks, and 3 ohm resistors to install on the shock electrical connectors to fake out the computers. After a couple hours the computer resets itself, and the dash warning message goes out. The car is supposed to ride just fine with the new standard shocks, just not as smooth as it would with the magnetic shocks. Still, for somebody on a budget, this option could save some money, and get you back on the road.

Incidentally, I believe GM has upgraded the magnetic shock system since my 07 Lucerne CXS went into production. The new systems have much faster computer control, and the shocks are designed to respond faster. So, it's is supposed to give you a smoother ride. Now I see Mercedes (?) working on some kind of "look ahead magic body ride" system that looks ahead on the road for even small bumps, and adjusts the shocks before you hit the bumps so you glide right over them. Now isn't that a novel idea. If they can actually make it work, it's going to put GM's magnetic shock system to shame. I wouldn't worry about it too much though, as the prototype system I saw required a near mainframe computer system in the trunk to make it work.
 
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txbarney

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Central Texas
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Can anyone post a schematic of the magna ride electronics? My ride is VERY firm (like a farm wagon) I tried unplugging and cleaning the electrical connection at the strut and that did not help.
Next I pulled fuse #6 that feeds the system and that totally changed the ride to like the shocks were shot.
I either have a bad connection or some bad module or sensor.
Looking for suggestions and help
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MelsRegal

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Regal GS 2017
The Chevrolet Corvette was the first GM car to use this system. The cars when shipped were equipped with plastic blocks to prevent the shocks from moving during transport. I believe this was due to the possibility of the shock being damaged if it was forced to move with no power applied to it. My point is, do not remove the fuse and then drive the car.
 

Johnscsx

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I'm sort of wondering what you mean by "VERY firm". Is this a new car for you, or did the car's handling suddenly change for you? It's a complicated computer that controls it all, I'm sure of that. The only thing a schematic would do is show you how the wires are connected to the computer module(s). And if it wasn't all working mostly as designed, you would see a message on the dash. (You can pull a single shock wire, and prove that. It might take a couple trips though.)

I believe that the suspension control system requires a lot more to be working than just those wires that are plugged into the shocks. There are also level sensors on the car, and I'm sure those sensor readings get fed into the suspension computer too. I wouldn't be surprised if steering commands get fed into there too, given that when the system is functioning normally, the car corners like a race car. Actually, that's one of the tests you can do, make a very fast corner at high speed, and see if it rocks back and forth or not. If it rocks and rolls, your magnetic suspension isn't working properly. Another test you can do is to stomp on the brakes at 20 mph. The traction control system will of course kick in, but the magnetic suspension system also keeps the car from bouncing after you stop. When the system is working properly, and you stomp hard on the brakes at 20 mph on dry pavement, the sudden stop will set your jaw into the back of your neck, so brace yourself!

That said, I think the suspension computer has a lot of tolerance for worn shocks. It never told me that mine were bad, long after they were in need of replacement because of leakage.

Another thing you can check is the exact height of the center of the fenders above ground. The front two should exactly match, and the same with the back. If there is nothing in the car, but one is half an inch higher than the other, and the tire air pressure is the same, then one of the shocks may not have as much fluid as the other. (check for leaks at the bottom of the shocks too)

I'm also thoroughly convinced that the worse the roads are, the shorter your shock life will be. If you drive in Michigan potholes all day, then your magnetic suspension isn't going to last very long. There may also be a learning algorithm in the computer that stiffens up your shocks if you have a history of hitting a lot of potholes, but I'm sure the exact algorithms GM uses to control their suspension systems is a closely guarded secret.

What temperatures do you typically drive in? I strongly suspect the shock oil is a whole lot stiffer in the cold winter months.

One thing I did notice when I replaced all my magnetic shocks is that it did firm up the ride a bit. Not a lot, but it was noticeable. That sounds counter intuitive, especially if you're thinking that new shocks are going to soften up the ride, but the opposite was true for me. I'm guessing that happened because the new shocks had the full load of oil, whereas the old ones were leaking and one had a noticeable amount of air in it. And of course you can compress air, but liquid oil is relatively incompressible.

I'm not sure, but I think those magnetic shocks use a fair amount of current when they are fully activated. Have you had any electrical issues lately, such as excessive battery drain, as might happen if the computer commanded all four shocks to stiffen up the maximum amount, and kept them turned on all the time? A small pocket compass next to the shocks might possibly probably show you if the internal electromagnetics were stuck on when the engine is running and the car is in park, because the whole thing uses electromagnets to stiffen up the fluid as necessary.

Still no luck? Take it to an auto parts store for a code scan. Some of these stores are better diagnosing computer problems than others, so be sure they can read suspension related codes before you go. My local O'rileys says they can read a bunch of codes from non-engine computer modules that other stores can't. I don't know if it's true or not, but it is certainly worth a call and won't cost you anything.
 

txbarney

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One reason I would like to see the working schematic for this car is to answer some of the issues you touched on.
The car I have is new to me, I purchased it from the original owner and I believe one reason he was selling was this and the navigation were both not working and he told me they wanted $700 to fix the navigation.

The only wires going to the struts is a two wire connector near the bottom, this is energizing a electromagnets inside the shock this coil surrounds the ports or channels that the fluid flows thru. The fluid has very small metallic particles....depending on the strength of the electrical signal being sent to the coils...the metal particles restrict the ports and change the stiffness of the shock/strut.

I drove the car over 2000 miles with the wires to the struts disconnected....no signal going to the electromagnets, the ride was not hard and there was enough extra rebound that you would normally say it needed new struts. I drove it today around 75 miles (freeway, in town, etc) and it is not as harsh as it was.....I am starting to wonder if the ports inside the strut might have been plugged.

Also I am in Texas so we are not talking extreme cold...50 today with 80 forcast for Friday.
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Johnscsx

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All four shocks have the magnetic fluid in them. The back shocks are connected to the computer via connectors on the very top of the shocks. To access this you have to open the trunk and pull the carpet out. The connectors pull straight up, if I remember right. If you only pulled the wires from the front, and not the back, then it could be the computer is trying to compensate for the problems with the front struts.

It sounds screwy, but I've got a theory that the front shocks help the rear shocks learn what's coming down the road. I say this because when you drive over a speed bump, there is always a lot less 'bump when the rear wheels go over it. The computer knows precisely the position of each shock due to feedback from the level sensor on each wheel, and it knows how fast the car is traveling due to the speed sensor on the transmission. It also knows what direction you're turning due to a transducer in the stearing system. (Did you ever notice the side marker lamp light up at night when you are going slow and start to turn , even if you don't have your turn signal turned on? This car is very smart.) What I'm saying here is that when you go over a speed bump, the computuer senses it, and then softens up the back shocks to help absord the shock of the back wheels going over the bump. So, if you disconnected the wires on the front shocks, but not the back, then the rear shocks may still be doing something for you, though only the computer programmer who wrote the embedded code could tell you what .

Due to the huge expense of replacing those magnetic shocks, some owners opt to just put regular shocks on there, and bypass the computer by installing low resistance resistors directly into the electrical connectors that plug into the shocks. Without those resistors I hear that you get an error message on the DIC after the computer has had enough time to determine it is not an intermittent fault. So, when you disconnected your front struts and took it for a long drive, did you get an error message on the dash after a while? I would be most curious to know.
 

SammyG

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I have 2007 CXS with the magnetic shocks. I was also told it was a sport suspension. Is this another level of the magnetic system or just part of the standard magnetic system on the CXS?
I had front struts / shocks replaced 8 months ago. It was $3,000 just for fronts. My ride has become very bouncey in rear of car. I could not find rear shocks thru any of the Auto parts stores or online. So , I went past local dealership and was quoted $800 a piece for the rear shocks. $2500 total cost to install. Needless to say I would like see if there is an alternative. My son can install them for me.
Where did you find rear shocks for $350 each? What kind of ride do you have by going with non-magnetic shocks on rear? Does effect the front magnetic ride shocks?
Thanks
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SammyG

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I have 2007 CXS with the magnetic shocks. I was also told it was a sport suspension. Is this another level of the magnetic system or just part of the standard magnetic system on the CXS?
I had front struts / shocks replaced 8 months ago. It was $3,000 just for fronts. My ride has become very bouncey in rear of car. I could not find rear shocks thru any of the Auto parts stores or online. So , I went past local dealership and was quoted $800 a piece for the rear shocks. $2500 total cost to install. Needless to say I would like see if there is an alternative. My son can install them for me.
Where did you find rear shocks for $350 each? What kind of ride do you have by going with non-magnetic shocks on rear? Does effect the front magnetic ride shocks?
Thanks
 

Kayaker

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Hello,

I have a 2007 Buick Lucerne CXS (60K miles) with a very leaky rear drivers side air shock. Bought new rear air shocks from Autozone and was just about to start my Friday night project when I ran into a electrical connector on top of the rear shock when I pulled the trunk carpeting back to expose the strut mounting bolt. Based on everyone's posts and a little looking around I guess I have that incredibly expensive magnetic shock system. Bought this car from my Mom and it is used exclusively by my wife and though this fantastic suspension would be nice to keep it is not in our household budget to replace. So now I need everyone's advice. What would you do if you were me? Should I by just one new expensive shock and replace it, but I see people have said these are typically only rated for 50-60K miles. Do I buy to shocks for the rear and put a resistor in the connector. Could I use my Autozone Gabriel shocks and put my own resistor into the connector? Any suggestions would be most appreciated?
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pcmos

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Putting a resistor in the circuit without a fuse is a bad idea. I've noticed a lot of people advocating this approach and there is a lot of potential for a fire. I'm an engineer so I can speak with some authority on this issue. An electromagnet coil doesn't act like a linear resistor in a pulsed DC circuit (similar to AC but with unidirectional current.) Measuring the DC resistance of the pins on the shock and simply plugging in an equivalent resistor is NOT going to replicate the coil. The coil inside the shock receives a pulsed DC signal from the suspension computer and the duty cycle (on time) of the pulsed signal determines the strength of the magnetic field. The coil, however, unlike a standard resistor actually opposes changes to the current in the circuit due to the frequency of change in the pulsed DC signal it receives. Coil behavior isn't easy to characterize in a pulsed DC circuit but generally the higher the instantaneous switching frequency the higher the resistance (called inductive reactance.) That means that the effective resistance of the coil during high duty cycle states is much higher than the DC resistance you measure on the bench with your multimeter because the on/off/on cycle occurs in a shorter time period. Odds are that there are very limited occasions where the computer tries to drive enormous amounts of power to the electromagnet (maybe an extreme high speed swing through a freeway ramp where it wants full firm for a long time) but during that time you could easily burn up a standard resistor and cause a fire. If you want to try a resistor in line I recommend buying a ceramic or wire-wound one, placing the whole assembly in a metal enclosure of some sort and wiring a fuse in line that would protect whatever gauge wire goes to the shock (maybe 16 AWG?) from full 12V (reality 13.5V) battery power.

That should cover your bases... if a high power load is sent through the line the ceramic or wire-wound resistor will be tough enough to take it, the metal enclosure will stop it from setting your trunk carpet on fire and the in-line fuse will blow if a current sets up that is high enough to melt insulation off the wires or destroy the driver circuit. At 100% duty cycle assuming voltage could peak around 13.5V and assuming you need ~2 Ohms (go as high as you can to limit current while still fooling the computer) to simulate the presence of the shock coil you'd see up to I=V/R=13.5/2=6.75A. 16 AWG (I'm guessing it's 16 to the shock connector) wire is usually protected by 7.5A or 5A on the conservative side... let's assume 5A for purposes of the resistor spec and place a 5A fuse on the line. Single resistor power dissipation in a worst case scenario P=IV=5*13.5=67.5W... this is pretty high for one resistor to handle... what happens if we run two 4 Ohm resistors in parallel. Rt=1/(1/4+1/4)=2 Ohms, each resistor sees I=V/R=13.5/4=3.375 A, P=IV=3.375*13.5=45.56W... much better. I'd spec two 50W 4ohm resistors in parallel encased in a small metal enclosure with a 5A fuse protecting the entire circuit for each corner you want to delete an electronic shock. If the fuse blows you know you are seeing some really high currents.

4 Ohm 50W resistors are used by audio folks to drive 4 Ohm speakers with an 8 Ohm amplifier... they are commonly available and usually come with a heat sink. Again remember that using two of these in parallel will give you a 2 Ohm equivalent resistance which should be about right to fool the computer but each resistor only sees half the current and therefore must only dissipate half the power.

https://www.amazon.com/uxcell-Wirewound-Aluminum-Power-Resistor/dp/B0087ZD07K
 
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gnu

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2010 Buick Lucerne Super
Has anyone tried the ARNOTT brand shocks w/ magnetic ride control for $149.79 each?
 
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