Steering pump or steering rack?

[xxvoicexx]

I am not sure if my steering pump or rack is causing it to be heavy to turn.

Car is w210 e270

When I turn lock to lock during idle, the rpm drop/ surge a little, during touching the maximize turn limit.

Any suggestions besides try to change whole steering system?

I want to change pump but seem like the pump has pressure because turning the steering wheel, touching the maximized turn the rpm drops/surge

Want to change the rack but feel like it's the pump not enough pressure.

 

[brandwooddixon]

I would suspect the pump rather than the rack, have you checked the fluid level?
I think that the 210 also has "parametric steering" whereby the amount of steering assistance varies according to road speed so there could be an issue whereby the pump is okay, but the speed signal is not.

 

[LostKiwi]

Do not ever hold power steering at full lock as it stresses the pump and rack (which is why your revs drop) and can damage both.

As you load up the pump it draws more power from the engine..
Perfectly normal behaviour.

When you say heavy to turn are we talking about while stationary with foot brake on? If so again perfectly normal as when the steering is turned to wheels will try to rotate. If 5ge brakes are on you're effectively trying to turn the steering against the brakes.

 

[Blobcat]

I’m presuming you’ve checked the tyre pressures and they’re not low leading to the heavy steering…