Hi everyone. Recently bought a 2016 M135. After about 5:6 months the steering became very stiff intermittently and went to BMW to have a look. They advised the steering rack needed to be replaced. I did this and replaced it with a second hand steering rack I found. After less than 2 months th exact same thing happened to the new steering rack and it is again intermittently very stiff and almost undrivable. 
Has anyone ever experienced this? Looks like my last option is to try a steering rack from BMW which will cost around £3k which I really don’t want to do. 

BMW haven’t been able to figure out what is causing the issue but I think something is causing the problem with the steering rack to bless I just got very unlucky with the replacement I bought. 

Thanks for anyone that can help

Morning Nick

Welcome to the Forum

I have read of issues caused by water ingress and other internal issues I have also read of several specialist companies who are refurbishing racks and giving Warranties with their work.

I would carry out an internet search for Repairers and talk to them. Remember BMW do not repair they just replace units so their price is based on the cost of the unit (plus their mark up) then their labour rates (North of £200 phr) all plus VAT not to difficult to reach £3k 

Good Luck

Dave