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2000 ML320, 2000 S430, 2012 Porsche Cayenne
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31 Posts
Discussion Starter #1
Front suspension sagging, but not enough to trigger warning light. I run on 20" wheels so they dip under the wheel well a bit. Just spent the past 90 minutes reading every post/sticky about the airmatic issues. I have a '00 S430 with 198K (mainly highway) miles.

- Pump & relay replaced in 2003
- No cracks with soap water test
- Thought it might be the valve block
- Decided to check the fuses (not relays) on the chart
- Checked 9, 32 & 46
- 32 was blown! It is the big orange one (must be for pump)
- I'll get a new one tomorrow and see if problem is solved

My questions:

1> With 198K miles, should I bite the bullet and replace all 4. Can these struts typically make it to 250K miles or am I tempting fate?

2> The airmatic is my most favorite feature in the W220. Rides like a dream. Are Arnott's conversion kits as smooth as OEM struts or are they the middle ground between springs and OEM air struts?

Thanks,
SB
 

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W221 & Audio Moderator
2013 S550
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10,979 Posts
Indeed, before troubleshooting any electrical problem - be it relays, pumps, switches, or anything else - check fuses. But then, investigate what may have caused the fuse to blow. Note that the most common causes of fuses blowing in the Airmatic system would be 1) pump failure; a seized pump will immediately cause the fuse to blow; 2) The relay failing in the "on" position, running the pump when not necessary, and burning it out - followed by the pump seizing and blowing the fuse.

The other failure mode of the relay (off) simply doesn't turn the pump on at all - and typically, would not blow the fuse.

The Encyclopedia has further discussion of the other causes of pump failure (mainly, leaks).

Personally, I would replace all 4 struts, but I don't have any "record" to go on. MB recommends replacing them 2 at a time (front/front or rear/rear). However, if you replace all 4, you're much less likely to be making repeated trips to the shop for airmatic failure. You'll have more time to enjoy your car. And when you ht 250K, don't forget to apply to MB for your hood badge. :thumbsup:

The Encyclopedia has links on the Arnott Airmatic replacements. They ride exactly the same as OE because they are exactly like OE except for the following: A thicker internal air bag, and better-designed seals.

One of the main causes of internal failures of OE struts is the constant rubbing of the air bag against the metal insides of the strut. Eventually it wears, and a hole develops. Thicker bag, longer wear. No difference in ride (pressure in the bags is the same).

The other principal cause of failure was an inadequate seal design. Arnott's has redesigned and improved the seals. They are no "middle ground." They are simply better. If you buy remanufactured Arnott struts, you are getting the same bag and seals as new Arnotts - and either choice is significantly less expensive than the OE Bilsteins.
 

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Registered
2000 ML320, 2000 S430, 2012 Porsche Cayenne
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31 Posts
Discussion Starter #3
Yup, you know your stuff Skylaw. Guess that's why you are the mod!

1> Replaced the fuse, car didn't rise
2> Swapped relay O (airmatic) with relay P (secondary fan).
3> Magic, the car rose!
4> But it didn't go back down when I tuned car off like it usually does.
5> Turned car back on, now pump is making growling noise.

I remember that same growling noise from 2003. Pump needed to be replaced at that time. So some combination of events fried the relay, blew the fuse and impaired the pump. Guess pump needs to be replaced again, unless someone has other thoughts.

Given my miles are mainly highway, I'm going to try and get 250K miles from the struts. Will treat myself to new struts when I get the 250K grill badge! Will report back once I change pump.

BTW, my dealer invoice from 2003 has the pump for $228. Today it is $317. Guess that's inflation.

SB
 

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2005 SLK350, 91 300SL with Pano Top, 04 S500, 2015 Tesla Model S
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2,085 Posts
Your pump is failing because it is constantly working to compensate for the strut leak. These pumps are not designed for continuous use. Replacing the pump without finding the cause is a short term solution.
 

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Registered
2000 ML320, 2000 S430, 2012 Porsche Cayenne
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31 Posts
Discussion Starter #5
Yes, you were correct. The strut was leaking.

Replaced with:

Arnott Airmatic Struts ($850 for 2)
Airmatic pump ($320)
Hella relay ($10)

Car once gain rides like a dream!

Returning the cores to Arnott today.

Thank you to the board.

SAB
 
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