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Just recently replaced MAF sensor to fix fuel mix problem. Works great, but now a new problem. It now whines like it's low on power steering, but it's slap full?! I have 0 clue where to even begin to look to find the problem. Help?

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Could it be that the power steering pump is just dieing? There is no way there could be a correlation between replacing the MAF and the power steering pump going bad. From your previous post, I see your ML320 is a '98 with about 188k miles on it. This is no spring chicken of a vehicle (whether MB or any other brand). Parts wear out and need replaced. Something you could try is getting the pump flushed. This might quiet it down some. –  Paulster2 Jun 4 at 14:08
    
@Paulster2 I didn't think the 2 were related, but as a "weekend mechanic", I really have no clue. Any suggestions on ways to test the power steering pump or other signs to look for? –  SpYk3HH Jun 4 at 14:57
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@SpYk3HH: You can jack up the front end, start the engine and then turn the wheels left and right. If the noise is still there, then it's probably the pump. Have you checked the belt for glazing or cracks? Could it be slipping? Sorry, trying to diagnose engine sounds without being able to hear the sound is a skill I don't possess. –  TMN Jun 4 at 16:45
    
@SpYk3HH : Why don't you post your MAF replacement solution as a comment in the other question? Isn't it great that you didn't have to replace your timing chain and ECU? :) –  Zaid Jun 4 at 19:54
    
Agree with Paulster2 and TMN. The rotary vanes inside the power steering pump will eventually wear with use and give a characteristic whine. One way to confirm the whine comes from the pump is by probing and listening to it with a mechanic's stethoscope. It isn't the most practical of tests since you need access to the pump while the engine is running, but it should put things beyond doubt. –  Zaid Jun 4 at 20:04
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If the fluid level is fine and it still whines after you turn the steering wheel from lock to lock 10 times, it could be that air is leaking into the system. You could have put pressure on the reservoir while changing the MAF sensor. Try refitting it with the new o-ring. If that fails, replace the reservoir itself and if that doesn't help, change the steering pump, you may have just been unlucky.

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TY, I will look into all that this weekend and update how it goes. Also, I assume by from lock to lock you mean sitting still and turning the steering wheel as far as it will go to the left and then right 10 times, correct? –  SpYk3HH Jun 5 at 17:40
    
Yes. Best if you do this when the car is on axle stands. –  user5122 Jun 6 at 8:35
    
Replacing the O-ring ... surprisingly seems to have shut up ... no idea why? –  SpYk3HH Jun 29 at 22:25
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