ML350 '06 ~100k miles
after i felt wheal is hard to turn i replaced power staring pump witch Chinese one. problem became less noticeable but symptoms remained and they are not typical for my understanding.
here is what im getting:

Cold start, all turns well and perfect, short city drives are all perfect.
Trouble comes with long drives, ex highway drive 50 miles, then city traffic lights then pulling into drive way after stop sign and 3 sharp turns and slow slow at driveay as i have 1/2" form mirror to wall then when I go reverse at parking lot to fit in my slot im looking power searing amplification, not a lot but i need to tuen much harder then regularly.

It feels like going reverse after longer drive it activates a problem, though logically reverse is at lower RPMs. So if i ramp engine for split second so car has no time to move that restores power staring to normal.

To me those are symptoms of pump problem (especially that this ML has no complex controls, more like nothing besides pump and cylinder on the line)

Overtime china pump became better but still shows some symptoms.

So i got not good pump? or some other ideas?

biggest doubt is that on cold start, and short drive all front and reverse works just fine, and power searing is not something tha get hot and more liquid so it would pass though the pump blades at when heated up
So im little hesitant to replace pump again

any thoughts?
maybe some one had similar symptoms?

 

The newer Pentosin CHF 202 has a tad more silicone anti-foam, and was developed for VAG cars. If you flush, try this fluid. I've switched to ATF, Dexron 6, but cannot recommend this because mixing those two fluids is a bad idea, you have to flush it completely. The added visc will give you more pressure though.

 

i can probably figure out how to flash system but not to a total clean,, just train old fluid. cruet flied is refresh MB cans from dealer.
more pressure i guess more leaks for now system is dry no leaks and we added new tank gasket so probably can be one option to try

 

Your fresh fluid is good enough. ATF is more of a track mod or extreme high temps, but worth mentioning.

Is there anyway you have blockage from a part dropped into the system?

I would seriously take it to a good mechanic to have diagnosed before you blow up the system. Why did you need a new pump to begin with???

I wish you could back flush it or at least purge any air. I don't really have any specific advice, except maybe to find a BOSCH Service Center near you, they are the best.

 

Did the Chinese pump come with a new reservoir?

After you replaced the Chinese pump, did you follow the bleeding procedure?

 

@Audi Junkie
I think if there was a blockage it would exhibit symptoms on cold stat low rpm or periodically at different situations
i had pump replaced because i had same identical symptoms but but at point that wheel felt like im on a truck form form 1940ss that's at the end of the day when reversing and pulling into driveway only
new pump gave same symptoms but at lighter level, i just feel more force needed

im kinda starting to suspect there maybe air in line? especially when new pump added. i can probably putt vacuum on cup and suck air out

@Maj. Dundee
pump was just pump, we used old resevruar

i did not replace it myself, so it was doen at garage, i have no idea what guys there did. my guess they just topped up fluid without bleeding properly

 

i did not replace it myself, so it was doen at garage, i have no idea what guys there did. my guess they just topped up fluid without bleeding properly

Before you replaced the pump, was there any noise while turning the steering wheel?

 

nope no noises even when going to far cut off corners. original pump (which i still have) is MB (bosh i guess) and it was my guess about 5-6 year old as when i got tha car it looked like pump was replaces by MB when they reconditioned car for sale

 

Then follow the bleed instructions and see what happens. Two people needed, one to turn the steering wheel and the other to look into the reservoir.

If there are bubbles in the fluid, continue turning until there are none. If the bubbles do not disappear, the reservoir must be replaced and the bleed sequence must be done again.

 

Hi, I had same thing it was better when cold got harder tp turn and it was whiny when turning. i thought it was pump to. but i order New MB reservoir on fcpeuro replaced it, new fluid got the air out of the system and BINGO. Very quiet no whining. i bet your pump was good i hope you didnt throw it out.
Filter inside the reservoir gets plugged up and its starts whining.

 

will try to bleed, if no air exits then will try new reservoir (or i can perhaps figure out how to clean filter?

 

Dont even waste ur time bleeding, just get a new reservoir install it then bleed it. Filter is integrated inside you cant really see it. Its $58 you not loosing much, just do it. I am glad i did, because i wanted to do the pump to and i am glad i didnt

 

What the heck? My manual says it takes MB PS fluid or ATF. I have to flush mine out asap.

 

I had noise(air) and inconsistent steering effort in mine.
Replacing the reservoir and doing the rack/bleed procedure did it for me.

I have a steep hill near my house that doesn't get much traffic - when I want to do that procedure I just creep up it and go lock-to-lock back and forth up the hill.
Lucas makes a viscosity improver for power steering fluid, it seems effective too.

 

So the actual tech is to use Pentosin if you are operating below -25c, and a full flush is required.
I started flushing Pentosin cars TO ATF a long time ago, for the converse reason; to get a thicker fluid for high/normal temps. Guys doing stuff like Baja style driving or doing doughnuts would overheat the system from runaway heating via visc reduction and metal-to-metal contact. They were pulling metal bits out of their system.

Just don't mix the two fluids. I was looking for the TSB relating to the subject. It's in the Pentosin literature someplace.

 

I don't know about Lucas, but if someone had a legit seal issue in the rack, they could use Maxlife ATF to offer a little seal-swelling effect. It's Dex II to VI backwards-compatible.

 

so im back here as problem continues,
i replaced reservoir and problem did not go away.
now as i have new pump (china aftermarket), fully bleeded, new resevuar,

im starting to think maybe rack cylinder seal is not holding when it heats up? my bigest problem is that its harder to reproduce symptoms
there are no leaks form rack itself

any ideas?

 

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1st one is lubricant, seams like its more to remove noises (which i don't have any) i can try it anyway maybe it help

 

any one knows what fuse goes for "speed valve" or how to check if that vole fitted to car?
i noticed steering column does not lock any more, no even motor sound. I had problems with fuses oxidized and not working for some time until they heat up... so maybe same happening to that valve... so wanted to check before putting any foreign fluids to the system. Any ideas?

 

I had a similar issue
I just bought a brand new pump and replaced, drained all the old power steering oil, and bought new one into it, started engine turned steer end to end and that fixed the problem!
my total cost was around $280