Freelander 1 Td4 Power Steering - Hissing ! SOLVED

Just bought another Freelander with 40k on clock. All is good, usual window / central locking issues but the one that is causing me some grief is a hissing noise (louder inside the cabin but only die to engine running blocking it in the engine bay). The noise is present when the steering is straight ahead, when the steering wheel is moved only 1 inch it stops. Sound is obvs coming up column. Power steering seems to work fine, no fluid loss etc.

Anyone had this? Can a worn rack allow fluid to be pumped around when power steering not being operaterd (turned) ??

Head scratcher - someone may just know !?!?
Thanks.....

A faulty rack control valve can give this hissing sound. Is the steering wheel straight when driving straight? I have come across a twisted torque link in a rack before now. This held the valve open when it should have been closed.
I'm sure that the Freelander uses a torque link in the rack too. It's a clever little link that keeps the steering effort constant for the driver. Basically the stiffer the steering to turn, the more pump pressure is applied to the piston in the rack. However if the rack has been subjected to excessive torque, the link can remain slightly twisted, opening a valve. This then circulates the fluid all the time, causing the noise.

Thanks - wheel is off to left a bit when driving straight. Can this link be replaced / repaired? All works well and MOT passed !! But the old chap that did it couldn't hear it - so he said !

If the rack is at fault, it's a replacement job really. They are easy to get second hand and aren't that expensive. Thankfully the Freelander doesn't wear it's rack out like many other cars.
I'd carry out a few checks first before condemning the rack. Look at the fluid without turning the steering to see if it looks to be frothy or bubbly. Also see if the fluid gets warm quite quickly, as this would indicate that it's being worked, when it shouldn't.

Thanks Nodge, just been reading up on changing the rack - if bolts and pipes come off o.k looks fairly straightforward ! That is a big IF !
Will look for movement in fluid and temp - didn't realise there was a cooler too.

The cooler is there for those that hold the steering on full lock. This will rise the fluid temperature very quickly. However while the steering is straight and unloaded, the temperature shouldn't rise much at all.

Some tests today. Fluid not heating up, no froth in reservoir. Lifted front of car, unlocked steering lock, turned wheels from lock to lock several times. PAS fluid came up over top of reservoir. Wondered if it could be air. Checked level and all settled. Listened and NO HISS !!!

Took car out for a run, Silence until I got home and then hissing again. So theory is could it be air and a slight leak letting air in again after bleeding and using?? Will be checking all unions next but any ideas welcomed !

Is it a 1.8? I'm thinking that it could be the pump inlet pipe has hardened and shrunk over the years. This happens sometimes and my be accompanied by dampness on the pump casing.

Thanks, clues is in the title ! TD4 !!

But will check all hoses when it is operating. There is a thread on here about hoses collapsing and being flat, then someone said a new one was also flat !!

Have found new factory rack for £165 so not end of world, bushes at top of struts are creaking too so will do that at the same time. Thanks for your help.

It does sound like it's drawing air into the system. The burp seems to suggest that too. I'd check everything very carefully before splashing out on a rack.

So finally changed the rack to a new one. I suspected the non return valve- fitted on one hose entry, but couldn't remove it so changed whole rack and the cabin is quiet !!!

Not a hard job, just fiddly aligning steering column splines and getting bolts back in to bulkhead with the other 3 arms required to fix it back in !!!!