New suspension all around - Low rear end

[rafadavidc]

2004 Ultra, GT suspension, 62k.

I installed new shocks in the rear myself a couple weeks ago. Kept the factory springs, compressor, air lines with compression fittings. Last week, I had entirely new front strut assemblies put in.

Now, the front wheels look proper in their wheel wells, but the rear wheels look like they're disappearing into theirs. I'm wondering if there's a ride height adjustment I need to make, or if I didn't reinstall the air line fittings properly and all the air is leaking out. The thing is, the compressor isn't running full-time like it was on the old shocks, so I don't think that's it.

How do I test for air leakage in the rear? Can I force the compressor into run mode and paint the fittings with a soapy brush?

Assuming any leak test passes, how do I make rake adjustments to this car? I assume that's essentially what I'd be doing.

Right now, it looks like a ghetto sled, and I know I'm taking a mileage hit in this position.

 

[pila80]

There's a height transducer under the rear, with an arm and link rod to the rear suspension. Not sure if it's supposed to be used/adjusted for height though. Seems to me that the rear springs set the standard height, and the air shocks keep it there when the cars is loaded.
I could be wrong of course, I was once, back in 1947....

 

[brfield]

To test the air ride, turn the car on and get a couple people to sit on the trunk (do it with it open). You should hear it pumping.
Other than that, I don't know about adjusting the height.

 

[rafadavidc]

It does pump. I was putting air in the rear right tire yesterday since it was low, and by sheer chance, the compressor was running right there next to my ear right when I was doing that. So, that functionality has been verified. Rear is still sitting low. What now?

 

[HotZ28]

Is the rear sitting lower with the new air shocks, than is was with the original? On an air assist rear suspension, the rear springs are different than non-air assist springs and are NOT designed to provide the primary level. Primary level is achieved only when the compressor pumps about 18-20 psi into the air bladders. When you say you heard the compressor "running", was the ignition switch ON? Are you sure the compressor is capable of pumping enough air pressure to inflate the bladders? If the level control sensor was working to keep the ride height correct before the shock change, nothing should have changed. ON my '96 PA, the level sensor lever is adjustable by loosening the nut that holds the lever to the sensor shaft. (I heard the later models may not be adjustable, but have not personally verified that)
A very small adjustment (1/8") makes a big difference (+ or-15-20 psi) depending on which way you move the lever. When additional load/weight is applied to the rear of the car, the level is adjusted by applying more pressure to the shock bladders. You need to verify that you do not have any major leaks, or that the exhaust valve is closing completely and not leaking air, then verify that the compressor is pumping adequate pressure. The compressor should be capable of pumping 60-80 psi. directly from the discharge of the compressor.

 

[rafadavidc]

When I heard the compressor running, it's because I left the car running while I ran out to fill that tire near the compressor. With the engine running, there was power to the system, and it judged that level was not achieved. It was attempting to rectify that situation. My head was right next to the compressor housing as I filled the tire, so I heard it distinctly.

The shocks I took off were completely blown. Ten-year-old rubber that got under-utilized by the PO. They were all leaked out and did not hold any air. As such, the rear sat low. I'm aware that the coil springs are not intended to provide primary level on this axle; I had a 2000 with the same feature. However, I never encountered the problem of continued low ride with new shocks.

How do I test for leaks? What about the exhaust valve? How do I test compressor output? Where is the level sensor such that I might investigate manipulating it? I imagine I could just fit some Schroeder valves to each shock and put 20PSI in each one myself, but I'd rather this system worked properly if all the parts are working.

If I'm going to guess, I'm going to say that the factory air line fittings didn't seal properly into the new shock fittings. Everything clicked in as intended, but it could be the o-rings didn't fit quite perfectly or something.

 

[pila80]

Good answer from HOTZ28. Most air shocks are supposed to have some air in them normally, so it makes sense to have enough to level the car in normal stance. I see the light !😀

 

[HotZ28]

How do I test for leaks?

Soapy water solution in spray bottle. Best to use dish washing detergent, such as Dawn, or Ajax. Both work well.

What about the exhaust valve?

The exhaust valve is located in the compressor head. It has two white wires going to it. It vents into the compressor intake line through a TEE in the hose. The rubber hose can be removed to see, or feel for any air leaks when the valve should be closed.

How do I test compressor output?

I cut one of the compressor discharge lines (the ones going to shocks) and installed a TEE (as shown below) and reconnected the cut portion of the hose to the TEE. I then installed a piece of 1/8" tubing to the on the outlet of the TEE which had a pressure gauge installed to the other end of the hose. You can make this gauge install either temporary, or permanent. I choose to make mine permanent (mounted in trunk) because I always like to see what the pressure is. If you decide to make it temporary, all you have to do is remove the 1/8" tube going to the gauge, and install a plug Part #3126 53 00 as shown below.
Legris Part #3104 53 00 Click Here

Legris Part #3126 53 00 Plug Click Here

 

[Pmish]

I just replaced all 4 shocks today. Same issue. Although it seems the front sits higher now compared to the rear. I can hear the compressor run for about 5 seconds and stops.

Keep me updated please if you find a solution.

 

[Lbsofsoul]

I just replaced all 4 shocks today. Same issue. Although it seems the front sits higher now compared to the rear. I can hear the compressor run for about 5 seconds and stops.

Keep me updated please if you find a solution.

Same here

 

[LARRY70GS]

There are quite a few cases of the front sitting too high after a strut change with Ready Struts. Sometimes the car will settle some after a while. On my Riviera board, lots of guys had this happen with Monroe ready struts.

The relay for the air ride is under the rear seat. If you locate the relay, you can pop the plastic cover off the relay and trigger it manually with something non conductive. That will make the compressor run.

 

[Lbsofsoul]

There are quite a few cases of the front sitting too high after a strut change with Ready Struts. Sometimes the car will settle some after a while. On my Riviera board, lots of guys had this happen with Monroe ready struts.

The relay for the air ride is under the rear seat. If you locate the relay, you can pop the plastic cover off the relay and trigger it manually with something non conductive. That will make the compressor run.

I have a 2007 lucerne. I have recently replaced all four struts and the front is higher.

 

[2007LucerneCXL]

You may want to post in the Lucerne forum, but depending on the strut manufacturer it may ride high then settle in 30, 60, 90 days or it may drop very little as there's no set parameters. Unfortunately strut manufacturers are making a one size fits all on some of their parts so the same strut may now fit many vehicles and not be designed for a specific model.

 

[Drakito]

The monroe all in one struts sit about 1.5 to 2 inches high for about 1 to 2 months and around 1000 miles before settling to level. The rear air ride should be normal height. If the wheels are tucked and in low rider mode there is something else wrong. Usually its an air leak somewhere, but the compressor itself can sometimes not pump, and the level controller is easy to knock loose on the control arms.

 

[Lbsofsoul]

The monroe all in one struts sit about 1.5 to 2 inches high for about 1 to 2 months and around 1000 miles before settling to level. The rear air ride should be normal height. If the wheels are tucked and in low rider mode there is something else wrong. Usually its an air leak somewhere, but the compressor itself can sometimes not pump, and the level controller is easy to knock loose on the control arms.

Thank you

 

[Lbsofsoul]

Thank you

I will take a look at my compressor and air lines.

 

[HotZ28]

Let us know what you find out in a new thread. This one is getting old (7-1/2 yrs) 🙄