WARNING: Power Steering Failure
 

The Vickers PN 126 460 2280 Power Steering pump on my 1991 350SD broke off! If this had happened when I was navigating a high-speed turn there could have been an accident.

I located a used PS pump from another 350SD and it also had a cracked mounting point. Me mechanic has said he has seen this several times before.

These pumps were found in 86-87 SD/SDL Turbo, 88-91 300SE/SEL, 91 350SD/SDL. Before putting one of these pumps back in your car check the mounting points for cracks.

My PS pump had obviously been partially broken for a long time because of the dirt in the cracked metal. If you are planning on a long road trip you might want to check this before you go. Rebuilding a used one is a lot less than buying one at the dealer.

The Vlckers PN 126 460 3580 is an equivalent pump. It probably has the same problem, as do many of the Vickers pumps.

Could too-tight belts contribute?

Didn't think of too-tight of a belt.
 

I hadn' t thought of the belt being too tight. Is the spring -loaded belt tensioner adjustable? It didn't look like it was when I took it off, but is there a turbuckle in there?

I have a 1991 350SD.

Is it a single serpentine belt?

The 300E is and it is adjustable. Maybe your is the same.

If so, I doubt you could get it tight enough to break anything.

Any chance of photos of the crack location?

Single Serpentine Belt
 

Yes, it is a single serpentine belt. The tensioner has a spring in there. I didn't think it was adjustable, but maybe it is. How do I know if it is tight enough, or too tight?

Here are the photos
 

My pump broke clean off. Shown in first picture. At the font of the pump the top and bottom mounting points on the left are broken. The back top mounting point is broken.

Based on the dirt in the cracked aluminum the top left front mounting point broke last.

The second picture is of a used one that I located from a ShopForum user. He checked the pump before he sent it and found a crack on the bottom left front mounting point.

You can see the pictures here: http://www.peachparts.com/shopforum/mercedes-benz-used-parts-sale-wanted/184019-need-86-91-126-used-power-steering-pump.html