ML 320 Power Steering quandary!

[theshark180]

Hi Guys, I hope I have posted this in the right place!
I have a 2000 ML320 with a curious power steering issue! Back in June the power steering stopped working but only when turning left! Perfectly fine if you only want to turn right. Took it to my indie who diagnosed a steering rack issue. The rubber boots were also full of fluid. He sourced a professionally reconditioned rack and fitted it (At considerable cost). All was fine for a month then exact same issue re emerged. A possible faulty rack was diagnosed and this was replaced by a different supplier. All was good for a few weeks then it happened again! It was then diagnosed that the power steering pump may be faulty causing the racks to fail. Hence another rack and new pump was fitted. 3 days after having the vehicle returned it has failed again?? My indie garage is at a loss as to what it could be. He has ensured that the correct fluid is used and has checked all the rubbers etc. The system is not leaking fluid and levels are good. Have any of you experts any idea what could be causing this problem please?
I love my old jalopy and have looked after it and thrown money at it and I really don't want to end up breaking her for parts!
Many thanks
John

 

[Taffy7hfa]

Must be something in the pipework causing an intermittent blockage.

 

[theshark180]

Many thanks for the prompt response I hadnt thought of that and will get my mechanic to investigate this avenue and will post the result.
Cheers
John

 

[theshark180]

I have just been to the garage who inform me that all the pipes were blown through prior to fitting the new rack and they dont seem to think that this could be the issue. They mentioned that the only part not changed is the cooler and that might be the problem. Would a faulty cooler only affect one side of the rack?
Thanks
John

 

[theshark180]

Apparently all the pipework was blown through clean prior to fitting. I have since discovered (although on a different model) that there is a set of valves inside the rack directing the steering fluid left and right and these can fail as a 'common problem' This would appear to be the logical explanation if the racks are similar. Just a little unbelievable that this would happen on all 3 racks unless something was amiss with the remanufacture process. The suppliers are now in the process of stripping the 2 returned racks to see what they can find.

 

[13enzy]

Must be something in the pipework causing an intermittent blockage.
View attachment 65993

hi, i have an ml 270 cdi auto (w163) 2002, i am based in manchester UK, how can i obtain a diagram like this one for my vehicle showing the steering system and also the cooling system.....Thanks

 

[ajlsl600]

Apparently all the pipework was blown through clean prior to fitting. I have since discovered (although on a different model) that there is a set of valves inside the rack directing the steering fluid left and right and these can fail as a 'common problem' This would appear to be the logical explanation if the racks are similar. Just a little unbelievable that this would happen on all 3 racks unless something was amiss with the remanufacture process. The suppliers are now in the process of stripping the 2 returned racks to see what they can find.

Possible if a repeated assly error but unlikely if racks are tested prior to despatch
I am guessing oil is cooled thru rtn line to tank after it goes thru the rack myvfirstvthoughtvwascfaultybor miss assembled valves, assuming they can be fitted in more than one way, position. really interested in solution.