Steering box issue

[RaceDiagnostics]

I took the merc out for a drive today, its not been driven or moved for 5 months, the steering was working just fine when I put it away but not now.

The problem only happens on a right turn (vibration and hum), when the steering is loaded up. No problem with the car jacked up and the wheels up in the air till the right hand end stop.

Checked the belts, tight, no slip.
Fluid level, at full level.
Felt for vibration on the pump, nothing, silky smooth.
Looked for the source of the sound, its coming from the steering box.
I can feel the vibration through the steering wheel.

Any thoughts, (a new box is £1200)?

 

[AVI_8]

Have you checked the fluid level?
If the box is knackered it can be reconditioned, don’t imagine it would cost more than a couple of hundred.
Western power steering in Bristol have a good reputation.

 

[Melvyn Best]

Might be worth flushing out the PAS fluid?

 

[Rannsachair]

Not sure if the relief valves are accessible, sounds like it could be the right hand relief valve leaking/damaged as you are only getting the noise when you are building pressure on that side. That is assuming there is a relief valve per side or does one valve operate both for both irections?

 

[RaceDiagnostics]

The box internals look like this.

The valve itself doesn't have any seals, I'm wondering if there is a bit of grit stuck in it but I'm no expert on how the box works.

Close up it looks like this.

 

[Rannsachair]

The reaction pistons look like simple relief valves: could be grit or a worn/damaged spring in one, though for the hassle of stripping may be easier to get refurbished by a specialist.

 

[Beeezer]

208 cdi?

 

[knighty]

I'd jack up, engine ticking over, spin the wheel full lock left to full lock right a few times... just to make sure there's no air stuck somewhere

also if it's something a bit gunked up or a bit stuck it might sort it out


worth a try before taking things apart

 

[RaceDiagnostics]

I tried that, there was no vibration till I got to full right lock, but didn't fix the issue.

 

[Burdekin]

Don’t know about the PAS boxes but is there play in the steering wheel? Boxes need a bit of play when the wheels are directly ahead otherwise they bind when turning.

Old Volvos with boxes the idler arm bush wears and folk over tighten these to compensate, maybe worth checking. Steering arms and bushes all good and toe in still correct?

 

[RaceDiagnostics]

The entire steering system is only 1000 miles or so old since a total rebuild and the box adjuster is just on the loose side of tight.

One thing I did do today was to check the three box mounting bolts were tight, they were fully torqued down. It was a long shot.

I'm going to drive it a bit on the off chance it fixes itself.

 

[Melvyn Best]

I had similar problems on a Mondeo that I was able to rectify by flushing out the system. Removed the return hose from the reservoir and capped it off , placed the return hose into an oil drainer then kept filling the reservoir while an assistant turned the steering from lock to lock . Pretty sure I used a 50/50 mix of ATF and paraffin first then neat ATF

 

[RaceDiagnostics]

Well I left it for 3 years in the hope it would fix itself, but no luck. Time to remove and rebuild.

If course, no way to get it past the exhaust.

So first a lot of messing about with the exhaust. Took off the back box and manipulated the middle box to release the downpipe.

Pitman arm pulled off.

Bolt out of the steering coupler.

And after about 2 hours, it's out.

Will rebuild tomorrow.

 

[RaceDiagnostics]

Pretty sure the problem has something to do with the valve in the middle, all I can do is try to flush it out as the the service manual says don't open it up.

 

[RaceDiagnostics]

All back in place.

Exhaust back on.

Filled up ps reservoir, then started up the engine, steering lock to lock, lots of grumbling. Topped up and repeated a few times but the grumbling continued!.

Went back to the pump, what a mess!

Once the froth died down I turned the engine over with the starter only and topped up bit by bit. That seemed to solve the issue.

Went for a drive and the vibration is gone. Result!