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Level control issue '96 SLS


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I have sold my 1996 SLS two days ago to a very nice elderly gent who lives about 200 mls away from me. He came and picked up the car and was very happy with it. While I explained him the features of the car, I mentioned the air compressor which runs for about 20 seconds every ignition cycle, so that he isn't concerned about the compressor noise.

When he arived home, he called me and said he hears that compressor noise all the time, whenever the car is not moving. He explains it does go off when he releases the brakes or shifts from D to N or P.

What can that be? According to the shop manual there is no relation between the level control and either brake or gearshift. Since the level control is incorporated into the suspension module, which may have interaction with gear shift lever position or brake actuation, there may be a connection though.

What do you think? Could that be an air-leaking shock or pressure hose? But if so why does it stop in neutral or park or with brakes released??

Or may it be something completeley different, and there is a noise but it isn't the compressor? But what could that possibly be?

Since the car is 200 mls away, I cannot pull the codes and I doubt that he can do it, he seems to be not technically inclined.

I offered him to bring back the car and I take it back refunding the purchase price, but else he's very happy (of course) and wants to keep it. I don't want him to take the car to a Cadillac dealer, heaven knows what they tell him. Their sole interest is making money, and I fear they will tell him horror stories.

He stated he'd like to de-activate the whole system, b/c he wouldn't carry any loads anyway, but I said it's better to keep it in working order.

I must say he is a nice guy and I want to get that straight, even if it costs me some time and/or money. If all else fails, I will drive up to his place and check out the situation.

Opinions please!

Thanks in advance,

Stefan (looking for '98+ SLS right now)

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I wrote him to remove the ELC fuse in the trunk fuse box as a diagnostic measure, if the noise he hears is the compressor, it will stop then.

I guess this will not trigger a "Service ride control" message, but may set a DTC.

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After working for years in tech support, i can say that the only TRUE way of finding out, is walking him through either the code reading, or going there yourself.

That being said, its entirely possible he is hearing a different noise, and is mistaken.

But if i were in your position, i would walk him through pulling the codes. Fastest, most reliable, and removes the "I think i hear something funny" aspect.

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There is probably a leak in the air lines - it shouldn't be difficult to find with some soapy water.

'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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Hi everybody,

thanks a lot for your replies. Today he called me telling that he brought the car to a Caddy dealer, because he didn't feel comfortable to diagnose it himself.

He also said that the rear of the car was high in the air, he didn't mention that before, even when I asked him, sigh.

So it seems like a sensor problem, or a linkage came off or something like that.

I will keep you updated as soon I know more. I hope they will not tell him a whole lot of crap....


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Car was brought to a Cadillac dealer for diagnosis. They checked the levelling system telling the owner the ride height is too high. They disconnected the compressor and bled the air. He says still high rear end(??).

Now for the interesting part: According to the owner the noise is still present with the compressor disconnected! What the hell might that be? I have an idea what might be the reason, but no way to check without going there. So I will visit him tomorrow and find out what's going on there.

While the car was in the shop, they told the owner rear brake disks are worn beyond safety. Of course they are worn, the car's got 130,000 mls on the clock and still the first rotors front and rear. But the guy's uncomfortable now so I bought a set of brake discs and pads and will install them tomorrow while being there.

Does anyone remember what size allen key I need to remove the caliper? I don't remember, was it 3/8 ?

I'll keep you posted.


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<rant mode on>

I'm losing my mind with this.

I went there thursday afternoon and drove the car. Guess what's wrong - nothing!

There is a ever-so-faint vibration detectable in the brake pedal, which is normal when the car is in gear. The engine pulls forward and "leans" towards the engine and transmission mounts, which transfers a little bit of vibration, but that's it. It may be that it is a little more on a 12 year old car than on a new one, at least the rubber has hardened and is worn over time, but it is really bareley detectable.

He THOUGHT that this vibration is the air compressor running all the time.

So I assured him everything is okay.

We re-checked all fluids, transmission, engine, power steering, coolant...all perfect.

I reconnected the levelling compressor and checked the system - ok.

Then we pulled the codes. I showed him how to do it so that he can read them out in the future. Except for a compressor history code (expected b/c it was disconnected), there were no codes present. Cleared the history code. Re-check: No system with codes here. I showed him that.

Since he mentioned that the Cadillac dealer told him that the rear brakes are close to unsafe, I had bought new rear pads and rotors and installed them right there in his garage. After finishing, I showed him both wheels spinning free with no brakes applied and both lock with either normal or parking brake. We verified that several times. After removal of the old brakes, he agreed that the old brakes are worn about 50%, and that the discs show wear, but are not unsave by any means. I did not charge him anything for all this, I even paid the brake parts. I also offered him to give the car back, at no cost for him. He refused.

So I left him thursday night with everything in good order.

Yesterday afternoon, just one day later, he calls that he was stranded beside the road with the rear brakes hot and smoking. He called roadside assistance. When they came, they lifted the rear of the car to find - nothing. Both wheels spinning free. They told him to drive home carefully and have the brakes checked.

My guess is that the parking brake release did not work, that's a known fault on my car, which happens 1 out of 100 times you drive off. When he bought the

car, I brought this to his attention and showed him how to use the emergency release lever in this case. The warning light works so you see when this happens.

Now the "Service Engine Soon" messsage popped up. WTF is going on there??? I tried to pull the codes together with him over the phone, but he can't do it. He can't write them down so fast as many show up. I offered him again (the fourth time now) to take the car back, to end all this mess.

He says he's gonna talk with his wife what to do and to call me back the same day. He did not call.

Additionally, he has not registered the car in his name yet, although it is written in the bill of sale that he has to do it within three working days. So he is still driving on my risk and my insurance and my tax.

I mean, what else can a seller of a vehicle do to make the purchaser happy? What is he doing to my car?? He told me that his previous car (some Lincoln) was destroyed b/c it caught fire while driving, is he jinxed??? Will I be jinxed if I talk to him again????

<rant mode off>

Thanks for listening.

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First thing I would do is cancel your registration and insurance, to start with, Second, how long has he had the car? If its more than 30 days, I'd have nothing to do with him, he's going to drive you crazy :huh: :huh:

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