...because I am ocassionally an idiot, I downshifted the SL from Drive to Second at about 70mph with resulting very high revs for the second it took to shift back to drive. Immediately thereafter - no power steering assist! I assumed I'd lost the belt, but no, the belt was there. Blown hose? Nope, no leaks nor loss of p/s fluid. Since I was out of town for the weekend I removed and completely dissassembled the pump - nothing apparently broken - reassembled and installed but no change.

So, what did I break?

Thanks.

fmb

70 mph in second shouldn't be above redline (although close!) if you have a three speed, fourspeed you definitely over-reved it.

My guess would be the pressure relief spring in the pump collapsed, so you don't generate any pressure at any speed now since the valve won't close.

Othewise, probably a blown seal somewhere, either in the pump (those are vane types, right?) or the steering box.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Hello Peter,

Actually, I mistyped - pulled the automatic from Drive to "3". Very high revs but no, I don't think I technically over-revved..just close. In any case, I drove the car home (200 miles of interstate - not bad w/o P/S because of that big steering wheel.)

I'm now looking at the pump diagram from the CD (mine has the Vickers light alloy pump). It may be that the volume control valve compressed it spring completely and moved all the way forward, then didn't re-seat. Rear section of the valve has a flat blade shape that from the drawing appears to seat in a slot at the back of the bore. I had the valve out, but without the manual I missed that detail. May be that I just re-assembled the valve in the "jammed open" position - so no pressure because the bypass is open at all times.

I'll post what I find when I get a chance to look at it again tonight.

..yes, this is the vane type pump. All of the vanes were in place - no evidence of mechanical failure in the pump so maybe I'm really luck and it's just an out of position valve. I hope so!

fmb

Well, that wasn't it. Took the pump out and went through it again. Everything appears to be in order. Still no power steering, no fluid leaking anywhere. Any ideas, anyone? Thanks. fmb

Rebuilt pump is $245 ouch, but maybe it is time. I don't see how you could have hurt anything by driving it in third at 70. I don't have to shift to forth on mine until 80 give or take, the SDL probably would only be turning in the low 4k rpm range at 70 in third. When was the last time your power steering fluid and filter was changed?

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I bought the car with 302k on it about 8 months ago. Pump was leaking so I replaced the bushings and main seal (on shaft under the pulley). New fluid and filter then, has been working fine ever since. My guess is that it turned about 4500 max. Not sure that the rpm spike caused the failure, but the p/s quit at that moment so... I'll probably swap the pumps with the 84 300D next weekend when I get back in town. I'd rather replace the pump than the steering gearbox ($650 rebuilt..ouch!). f

Your better off getting a used gearbox. I need to replace mine but why spend $500 on a rebuilt when I can get a very low mileage used one for around $100.

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Sometimes the most simple solution is the right one. Dead P/S pump. No leaks and from what I could see nothing broken inside, but I obviously overlooked something. In any case, 20 minutes to replace with a $35.00 salvage yard pump and the car's back on the road. **Tag on replacement pump indicated 65 Bar while original said 80 Bar. No noticeable difference -steering works great.

fmb