Hi everyone

Sorry if this is a repost, I did a search and didn't find what I was looking for.

So I bought my car about a month ago, on a Saturday.
Sunday evening, on the way home, the power steering just goes completely.
Thankfully this was right outside my house, so after a lot of muscle exercise, I was able to put it into my garage.
Next morning the mechanic arranged a tow truck and took it to his place.
He replaced the power steering pump and cleaned all the lines etc.
A week later the power steering goes again, but not as bad as the first time.
I was able to drive it, but it was just tighter than normal.
The mechanic advised me to take it to a mechanic that is a friend of his (I was about 600km away from home when it happened). The 2nd mechanic looks at it and notices some metal fillings in the bottle. His assumption is that the first mechanic didn't flush the system out properly when he replaced the pump.

Now for the weird part....
The mechanic plugged in his computer, cleared any faults and the power steering was back to normal. About 3km later, it goes back to being tight.
So I drove it back home, as it was 99% freeway and mechanic said it would be fine.

Back with my mechanic, he puts another brand new pump, removes the rack, bottle, cooler etc etc. and flushes everything out.
Car is fine for under a day, and the steering goes tight again!

Go back to him, and he does some calibration reset for the steering, and the car is fine for a few kilometres and then back to being tight!

There is no faults on the system, so don't think it could be an electrical issue.
Mechanic advises putting a thinner fluid as that should help.

Sorry for the long dang post, but just wanted to cover everything, and really don't know what to do next!

 

I am not the expert on power steering but a few things. Firstly changing to a thinner fluid is not a fix it is your mechanic not able to fix the actual issue and grasping at straws, I would not accept that as any type of solution or even try it.

Second, has the reservoir been replaced, it has the filter built in and is a know problem point and should be replaced especially since you said they saw metal in it.

Rob

 

So he says that Merc recommended changing to the newer fluid (which is thinner) with the new pump.
How true it is, I can't be certain, its just what he mentioned.

Regarding the reservoir, yes both the reservoir as well as the filter was replaced.
This time around when the steering went tight, I checked the reservoir and there is no visible fillings in there.

 

the filter is integrated into the reservoir so by replacing one you must replace the other. I’m only stating this bc it sounds like either you or your mechanic might be confused on this topic.

have you noticed any leaks? Almost sounds like you are losing the hydraulic assist

 

Mechanic replaced the reservoir, so filter would have been changed as well.

There are no visible leaks anywhere.
I suspect that there could be the slightest of tears on one of the lines that is allowing air into the system, but not enough to see oil dripping on the floor unless it would be parked for a long period of time.
However, there are no bubbles showing when turning the wheel with the cap of the reservoir off.
Is there any way to test for leaks? Like a pressure test of some sorts?

 

did some more reading and saw that although it is a hydraulic system, there is an electronic power steering proportioning/control valve. any chance this could be the culprit? If youve replaced the filter/reservoir, fluid, and pump (and belt?), i dont know what other components to check unless there is something wrong with the rack itself.

 

So my fear is it being the rack.
I am not sure if any belts were changed, will ask him.

He did mention that he would change some solenoid. I can't remember which solenoid it is, I will ask him and let you know.
Hopefully that fixes it.

 

Mostly its the SPS solenoid. It varies steering assist with speed => High speed = heavier steering Low speed = light steering

 

So I posted an update, but it clearly didn't update so here goes again....

So the mech replaced the solenoid as instructed but no luck, car still did the exact same thing.

When he removed the pump, he noticed that the part number on the current pump does not match the number on the pump that came with the car.
He did some digging, and realised that the part numbers have changed between Pre F/L and F/L.

So the pump that he put on the car was actually from a pre F/L, and my car is a F/L....

He ordered a new pump, that matches the part number of my original pump, and installed it.
I got the car back for about 2 weeks now, and everything seems to be fine (touch wood).