I have a 2014 E350 with around 127,000 miles. I recently noticed what I would say sounded like a whining noise you would normally think is related to the power steering system usually because the fluid is low. So logic states you try the cheapest thing first. I look under the hood for the reservoir and can't find one. So I do some googling and I search my VIN number to see what factory options my car had equipped and it turns out I have EPS system instead of a belt driven one. I can't find any videos or info out there about the one equipped in my car. I read that some are closed systems and that some don't even us traditional power steering fluid. The whine matches and gets higher pitched with engine RPM. I haven't tried to see if the whine also matches when the steering wheel is turned. The steering is still buttery smooth and I haven't gotten any warning on the dash about the power steering system. No visible leakage either, but I still like to figure this out before it gets worse. Could it just be pulley going bad and have nothing to do with the EPS system? If there is a previous thread or if anyone has info on the EPS system I'd really appreciate it. Thanks for reading

 

-- Electrical Power Steering uses a standard rack & pinion assisted by a strong electric motor.
There's no fluid, no pump whining and the belt has teeth like a T-belt.

-- That leaves only one choice for belt kit repair: the multi-ribed serpentine Continental belt + tensioner + idlers.

-- As to which accessory causing the whining... perhaps the water pump? Loosen the belt to check loose accessory bearings.

-- Remember the genuine parts are cheap, the services added on top of parts, no so much. This may be an easy job, at least the belt kit is.

 

My 2014 C350 is I think hybrid electric-hydraulic (or maybe just hydraulic). The reservoir is next to the oil filter.

 

So MY'14 features a mix of power steering:

• E350 has electric power steering rack
• C350 has hydraulic power steering rack

 

Maybe start the car with the hood open and get an empty paper towel tube, put it to your ear and point it at alternator, air pump, water pump and Idler pulley, if necessary have someone increase RPM's so you can be sure, likely the serpentine belt idler/tensioner pulley, but good to check first.