MB E350 CDi (265hp) Sport 2010.
Hi members, I have tried to find a similar post unsuccessfully so I hope that this isn't a repeat.
One of the hydraulic steering pipes (

Expansion pipe

MB 345.0 fluid
- Expansion Hose according to EPC) developed a leak from the inside - there was no evidence of scuffing or rubbing against other components and I've never seen that happen before. Anyway, I replaced the pipe and if anyone would like to know how to do this job then I'd be happy to share. I looked up the correct fluid in WIS - MB345.0 and bought a litre of Liqui Moly CHF Synthetic Central Hydraulic Fluid Power Steering MB 345.0
Following MB instructions, I topped up and slowly swung the steering (wheels off the ground) from side to side 30 times and another 20 for luck after leaving it overnight. Then I started the engine and all sounded well, the steering was clearly working with no obvious noise from the pump. However, when I got the car on the road I got some low but acceptable noise from the pump but with heavy steering. Has anyone had this issue before? I feel as though I am using the wrong fluid but before I start again with genuine MB fluid, does anyone have any suggestions? Is it possible to flush the fluid without removing the pipe again? Thanks in advance for any advice.

 

I think you've got the right conclusion about thin oil into your steering system.
You multiple air bleed did the trick for sure. 2 or 3 full turns should do.
So it's not air in the line causing this

Do you have an engine "oil extractor" or electric pump???

Use it to suck wrong fluid out :

1. suck steering pump tank once
2. turn wheel one way then suck tank
3. turn wheel the other way the suck again
4. Refill tank and rack.

Let me ask you how old is your serpentine tensioner + belt???
They can stress the steering pump pressure regulator with surges. This pressure surging help destroy old pressure hose.
Replace these cheap parts at once as a complete set with idlers so your new pressure hose will last long.

 

Thanks for your comments CaliBenzDriver. I changed the belt at 52k and 90k each time I did the fuel filter because of accessibility. The car has just passed 92k.
I want to understand why the fluid that I bought has the wrong viscosity when it's advertised as correct; after all, I doubt that Merc make their own fluid.
Thanks again.

 

I see... you said belt but the key component of this system is the tensioner itself.
Perhaps your steering pump filter is plugged up by all the rubber pieces disintegrating. That would prevent building up necessary pressure.
It is built-in the pump tank itself.

 

Thanks again, CaliBenzDriver. The mystifying bit is that the steering was perfect until I changed the pipe and fluid. However, the tank is pretty cheap and fairly acesible so I'll definately change that. I'll do the tensioner and idlers next belt change.
I appreciate your suggestions. regards, Chris

 

the funny thing is I've just watched a presentation about this last week by Ken from mercedessource in Washington. He stressed replacing the tank and its O-ring on the suction side.

Regarding the fluid he said by it locally which you did.... perhaps your steering needs a specific viscosity - MB likes to keep changing fluid specs and parts so it's difficult for anyone to source matching replacements, genuine or aftermarket.

 

Hi again. This tank is seperate from the pump and I'm aware of the common leakage point at that o-ring on the composite pump/tank models. I have contacted Liqui-Moly and they are confident that I've used the correct fluid, suggesting that I continue to try to bleed the system.
Today (car on floor), I'm going to run the engine for a good period without ttouching the wheel but starting on full lock so as to fill one sided of the ram cylinder only. This should clear all of the lines and cooler. Then I will move slowly onto the other lock since, theoretically, any air must be in that chamber, the valve or the ram supply pipes. In other words, I'm getting a bit desperate!
regards and thanks once more for your interest.

 

Jtlyk that this was the solution. After I did as I said in my last post, I took the car to a big pub carpark just over the road and went round and round in circles for 10 minutes! It is now back to 95%, self-centering and generally as good as I've had. I am expecting the remaining air to slowly percolate into the tank over a few miles. Thanks so much for you suggestions and time.

Regards, Chris