Is Anyone Here Familiar With ASD/SLS Systems? I Have Questions And Can't Find Answers - PeachParts Mercedes-Benz Forum

Squiggle Dog · #1 09-23-2017, 01:24 AM

My roommate has a 1991 W126 350SDL with ASD (but not SLS, though it uses some of the same components). The ASD system is ran by a tandem power steering pump. There is a reservoir on the left (driver) side of the engine compartment.

The tandem power steering pump is failing. It is very difficult to turn the steering wheel, especially at low speeds. We searched around and bought the last two rebuild kits in existence (we tried practically every imaginable vendor, including The Classic Center and eBay--all ended up backordered or out of stock with no ETA after paying).

When the engine is idling, at the rear of the vehicle by the ASD valve at the rear axle, every few seconds it makes a hissing noise. The hose that goes from the tandem power steering pump back to the valve lifts up and then slaps against the engine oil pan in sync with the hissing noise.

The vehicle has also had intermittent acceleration problems which MAY have been due to clogged fuel filters.

QUESTIONS:

1. Is the HISS...HISS...HISS... sound by the rear axle normal for ASD vehicles, or does it indicate a problem?

2. Is the hose from the tandem power steering pump back to the rear axle slapping against the oil pan normal for ASD vehicles, or does it indicate a problem?

3. If there is a problem with the ASD, will it cause drag on the tandem power steering pump, possibly causing difficult steering or poor acceleration?

4. Is it possible to put the system into a bypass mode where it will not interfere with drivability?

5. Are there O-rings where the hard lines attach to the cap at the top of the ASD reservoir? EPC shows no O-rings, leading me to believe they are flare fittings, but it looks like the cap is plastic, leading me to believe it should have O-rings.

I have done lots of internet searches on the topic and am not finding much of anything relevant. I looked in the factory service manual and it only shows diagnosing using electronic codes. If my roommate could afford shop rates, I wouldn't be working on it, plus I have a feeling there aren't any shops that would know how to fix it, or would be willing to, anyway.

I have to get the tandem power steering pump on this car rebuilt before my roommate completely loses steering on his daily driver. But, the ASD system is completely unknown to me and is integral with the power steering system so I have to be sure the ASD system isn't causing problems.