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Old 11-04-2001, 01:35 PM
EricSilver's Avatar
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Location: Fairfax, VA
Posts: 1,209
Power Steering Loss & Smoke

1989 260E, 160,000 miles.

Whenever I start my car for the first time in the day, or after it's been sitting for along while, I lose partial or total power steering at idle. As soon as I start moving, even slowly, normal behavior returns -- except on lock to lock turns where there is stiffness and resistance.

I thought I had air in the system and turned the wheel lock-to-lock to bleed it, which seems to work and the wheel can be turned easily with one finger. But after the car has been sitting, the problem returns.

Today I briefly noticed some whitish/light gray smoke when forcing the wheel lock-to-lock while parked, but that stopped once the wheel became easy to turn. I also noticed that the engine revs dropped noticeably during the forced turn.

Steering fluid level is normal. Recent work on the car has included a water pump replacement, and replacing a ruptured water hose which leaked a lot of water and coolant into the water pump/power steering pump area.

I will probably stop trying to force it in the future since it seems to correct itself during normal driving with a lot of cornering (and especially after seeing that smoke).

Any other ideas?

Eric Silver
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Old 11-04-2001, 02:10 PM
David C Klasse's Avatar
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Location: Mission Hills in the City of San Diego
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I recently found out that when you turn the steering wheel to lock, the RPMs do drop... and that this is normal. The power steering pump uses up to 9 horsepower, and the idle speed controller doesn't know when you are going to turn the wheel to lock, so it takes a second for the RPMs to correct itself.
I hope this helps atleast a little!
2006 E350 w/ 155k miles (Daily Driver)

1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
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1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)
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Old 11-04-2001, 02:26 PM
EricSilver's Avatar
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Location: Fairfax, VA
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Hi David,

When the car is initially started, and the steering wheel is really resisting, the rpm's drop and stay down, although once the problem self-corrects, there is no noticeable drop in power.

I have also been reading the thread about using ATF instead of power steering fluid. I added ATF this past winter/spring and since that time I have noticed minor to major leaks, which go away by themselves. I will probably put proper PS fluid in instead.

Eric Silver
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Old 11-04-2001, 03:26 PM
Mike Stone
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Now the weather is getting colder your PS fluid is thicker first thing in the morning.

I would suggest that you check the tension on the PAS belt. I think that is what you are seeing smoking as it slips.

Probably better to replace the belt if this has happened much as the heat generated when it has been slipping could have carbonised the pressure surface and this would have taken on a polish. Once polished you will never get it to return to origional "grippy" finish.

Mike Stone
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Old 11-04-2001, 07:39 PM
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Join Date: Aug 2001
Location: Evansville, Indiana
Posts: 8,150
Sounds like you need a new serpentine belt. Hot glycol and rubber belts aren't a real happy combination, and you probably glazed the belt while it had coolant on it. A new one should fix the problem.

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!
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Old 11-04-2001, 09:05 PM
Join Date: Jul 2001
Location: Old Lyme, Connecticut
Posts: 3,596
I would also suspect the pump is having a hard time keeping up at low rpm if you have not changed the fluid and filter in the power steering system in a while.

With a filter element clogged, the suction supply to the pump is choked off and the pump will cavitate. Once the pump starts to cavitate the power steering system loses the pressure supply it needs to provide the power assist. And you get a kind of chunky response when you turn the wheel. When the pump builds some pressure, the wheel responds as you expect, and then, once you move the wheel some, the pressure fades as the pump is starved for fluid on the input. And the assist dies, the resistance goes up and the wheel feels like it is freezing, so you stop moving it. Then the pressure builds and the sequence repeats itself.

Changing the fluid can be a messy job, and I have tried sucking it out of the reservoir using a chicken basting bulb, and disconnecting the return line from the power steering box and doing a fill and drain operation with the car running. The first way is the easiest, as you just draw it all out, change the filter element, fill it with new fluid, and run the car for a minute or two. Then you repeat the process (minus the filter element) until the fluid is clean and clear, like it comes out of the bottle. Takes a lot of fluid but it works.

The other way depends on the set up of your pump and I am not familiar with your model car. But the idea is to use the bulb to lower the reservoir level, then remove the return line from the steering boost cylinder and have it drain into a coffee can or the like that is about 2 quarts or so. Change the filter element, and have someone start the car. Add fluid as the level drops, and when the fluid going into the can is clean and clear like the stuff coming out of the bottle, shut the car off. Put the line back into the reservoir, top off the reservoir and close the unit up.

Hope this was not too long and helps. Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)
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Old 11-05-2001, 09:05 AM
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Location: Fairfax, VA
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Mike, PSFred, Jim:

Thanks for the info and advice. It seems the ATF is indeed too thick when the temperature drops (but is fine once the car warms up), so I want to replace some of it with PS fluid (which is noticeably thinner) to thin it out.

Is it OK to mix ATF with (red) PS fluid? I plan to drain the ATF from the reservior and replace it with PS, but some ATF will obviously still be in the system. My assumption is that this will produce a mixture thinner than pure ATF, but thicker than pure PS.

Eric Silver
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