SO being one of the first people to do the w215 ABC to coilover setup swaps. I realize this is probably the last subforum to ask this question in, but here it goes

I switched from the ABC tandem pump to coilovers and the traditional w220 regular power steering pump. this worked great for a couple years until I had a high pressure hose blow. i ended up losing most of my power steering fluid because of this

So i took the hose to a hydraulic shop and they said it was fixed. I reinstalled it thinking everything would work but I guess my power steering pump was already blown from when i originally lost all my fluid.

The engine seemed to struggle to power the steering pump and made a terrible groaning noise. Power steering pump actually ended up producing smoke from when I tried to run it. So i removed the pump

I got a used power steering pump from eBay. They go for only $45/50 USD these days which is great. My first $45 one lasted a while for only being $45

I installed the new pump. And BEFORE STARTING THE ENGINE i jacked the front wheels and bled the power steering system by turning the wheel from lock to lock (left to right) each way 10 times. I've done this exact bleed procedure before so I know I'm doing it somewhat correctly

Thinking everything is good to go, I start up the car and the NEW power steering pump STILL HAS A LOUD GROAN/sorta grinding noise. So I tried to bleed the system 2 or 3 more times with the engine off

I did some research and saw someone mention you should do the bleed procedure with the ENGINE RUNNING to fully bleed the system since it is a self-bleeding system. I tried that and the noise slightly improved but the groaning still persists. I can tell the pump is slowly failing because it starts to smoke if i let it run for more than 10 seconds. I would hate to blow another pump

Before you reply, I read the countless threads where expert user "43spd" mentioned you need to verify your reservoir filter is in good condition. If not, it causes a cavitation effect that produces more air bubbles. My last step before closing up the garage today was to remove the reservoir and the filter seems to be in great shape. It is not blown. I even stuck a drill bit in the opening to verify the filter was still holding strong. Filter feels firm, I can still blow air through it and suck air through it with my mouth gently and everything seems fine. AKA - Reservoir filter feels great

I know what a bad reservoir filter feels like, because i purposely busted one of my scrap reservoir filters with that same drill bit. So i would firsthand understand how it feels when the filter is busted

I noticed another expert user "Erik" mentioned sometimes the power steering rack can fail in m113 engine equipped vehicles (M class and so forth). Erik is great and really helped my finish my cl500 to cl55 amg engine swap when i ran into dead ends. Hopefully he can provide some clues as to whats happening here

Did i just so happen to order a failing power steering pump? Seems unlikely to me, new (used) pump seems to be in great condition. Reservoir O ring doesn't leak, reservoir built-in filter seems to be in good health

My only idea left is the steering rack but I'm tired of throwing money at this issue

I notice some people have lifelong power steering pump whine on m113 engines but mine is obviously burning up hence the smoke it produces with the awful groaning noise

Some people say just drive the car and after a few miles the Ps system will bleed itself. I'm not taking my chances....