Steering violent kicking!!

Diazalon

New member
Hello!

I have a 2001 Mercedes Sprinter 211 CDI MWB, right-hand drive, and I've been working on the steering rack for a few months now. I'm a self-taught, DIY guy when it comes to mechanics, but after the van failed its MoT due, in part, to a leak in the steering rack, I decided to try to fix it myself. I've got as far as finding the leak that needed repairing (in one of the fluid pipes running along the length of the rack between the rack and the chassis), replacing the part and reinstalling the rack, topping up the fluid and bleeding the system by turning from lock to lock with the engine off.

When I turn on the engine, however, the steering wheel (and whole system) starts to buck back and forth, quickly and violently as soon as I try and turn the wheel even slightly. It then just continues to sit there kicking back and forth in the same motion until I turn the engine off.

On inspection after, there is then a lot of resistance in the system when I try and turn, sometimes resisting so hard I have to counter-turn a little to be able to continue the rotation.

This led me to believe that there are air bubbles trapped in the system. There is a sound like bubbles of air are being drawn into or through the rack at pressure as I turn the wheel from lock to lock, approx one rotation away from full right lock, even when the wheel is turned with the engine off. It's a sucking sound, similar to the sound liquid makes in your mouth if you swish it around.

I can sit there and turn from lock to lock and it seems to get better as the air is pushed through and out of the system somehow, but as soon as I turn the engine on, the kick back and forth returns as soon as I try to move the wheel, in either direction.

From this, I thought then that there must be air being pulled into the system somewhere as soon as it's under the pressure of the pump. I found the pump was leaking a little, thought it might be that, replaced it, it works fine but the problem is still there.

I had a little look on the other pipes that run from the rack to the engine but can't see any fluid escaping, which I assume I would if there was a hole that then sucks air in under pressure.

I took the rack off for the umpteenth time and wrapped all the ends of the pipes and their connects to the rack with PTFE plumber's thread tape. That's all airtight.
No wear on the copper sealing rings that I can see, and have now also been wrapped in thread tape.

Is it possible there can be a leak in the rack itself?

Does anyone know what would happen if the pipes that run along the rack were connected in reverse, i.e the long pipe is screwed into the top hole on the top of the rack and it's meant to be connected on the bottom, or the small pipe is connected to the bottom and is meant to be on top?

I'm a bit stumped. Any/all ideas are appreciated.

This is my first post on here, so please ask if there's any more information I should include.

Here is a link to a short video I made of the problem in action: https://youtu.be/OninNyZcWVE

Cheers
 

koenb

Active member
It seems like fluid pressure is being supplied to both sides of the rack piston at the same time, thus fighting itself back and fourth. What are the chances a line is crossed or you may have damaged the input shaft/rotary valve during removal.
Edit: FWIW its best to avoid using teflon tape on threads for fluids, better to use a thread sealant like loctite 542 but shouldn't be required if the seals are good. Typically copper seals are a one time shot and need to be replaced every time.
visual aid ---> https://www.youtube.com/watch?v=eudfJPHf7DE
 
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Diazalon

New member
Thank you all for the responses! Spot on, I had the hard lines reinstalled the wrong way round. What a headache!

Rack is now reinstalled and fully operational. I really appreciate the help, my van and I would have been lost without it.

That video is great, it's really good to finally understand the inner workings having tinkered with the outside for so long. I'll look for more of that kind of thing next time.
 

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