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300Tdi Power steering - system bleeding after fitting a new steering box

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Hi all,

I’ve done lots of things on the Defender over the years, including changing the PAS pump. But until today I hadn’t changed a PAS steering box. 

It’s in place and connected, but when I tried to refill it I think I only got about 500ml or so into the system before it stopped draining out of the reservoir. I’ve searched on here and read the often-offered advice about turning the steering side to side. I’m OK with that and can find an assistant to help, but can I check this is done with the engine off?

The WSM is very specific about not turning on the engine/running the pump until the reservoir is full so I’m assuming the “lock to lock” advice is with the engine off?

I’m not expecting to get the full 3.4L into it, which is the quantity listed in the manual. I reckon there was only about 1L in in the drain tub , though there’s likely some still in the old box, so I don’t think it will be completely empty. 

Any advice gratefully received.


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Thanks very much for that. I was concerned that 500ml in the system would soon dissipate through the box and pipework and possibly leave the pump scavenging a bit. I guess I need to stand by with a jug of fluid and keep on topping up as someone else is doing the lock to lock thing. 

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Thanks again. 

I’m not expecting a ‘problem’ as such - hoping it will all go nice and smoothly. I was really just clarifying that point about ‘lock to lock’ with engine running vs the WSM saying ‘don’t run the engine’. 

I’ve decided not to do this today. I’m waiting for new steering shaft UJs to arrive, and some new fixings for the steering box itself. They’re due on Monday so the way the weather is I can’t really see the point in rebuilding with the old stuff, just to do it all again the next day. I have till Wednesday for the MOT re-test and this is all that needs doing now.

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On 12/17/2022 at 8:40 PM, Bowie69 said:

Don't overfill..... or when you switch off you end up with a stream of ATF shooting out the breather hole..... 




Ah well…. Good advice. I won’t say I “ignored” it as I was watching how much was going in, and putting more fluid in just as quick as the reservoir was being emptied but then it did that frothy thing and I now have ATF on both sides of the engine bay… 

On the test run something (pump or new box?) was girning just like Chewbacca in a grump, but it seems to have settled down now. Test run was through a residential area, lots of 90’ lefts and rights to get the steering going from side to side. The steering feels fine - same amount of effort or assistance as I remember before

I reckon I have only got about 1.2 - 1.4 litres into it though. Considering that the reservoir was empty, and it was a new pump, that doesn’t sound like much when the WSM says 3.4L. 

I’ll check the levels again before I take it for the retest tomorrow morning, but would anyone think a go at bleeding through the bleed nipple on top of the box might be worth considering?

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2 hours ago, Northwards said:

I’ll check the levels again before I take it for the retest tomorrow morning, but would anyone think a go at bleeding through the bleed nipple on top of the box might be worth considering?

I've never had to do that.

As Bowie says, if it's gone quiet and the reservoir is at the correct level and not frothy, you're probably good. Worth checking again after a few miles.

BTW it may be easier to jack the front axle up & turn the steering lock to lock than drive round the neighbourhood trying to swerve around ;)

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^^^ Ha ha! I'm not quite that daft! 😄 

When I first ran the engine and was filling the system I had my daughter doing the 'lock to lock' thing - and the car was on the big jack. 

It was the next stage where I hit the street - where the WSM talks about doing a road test with "rough surfaces; harsh braking and using both locks" or words to that effect. 

In fact I was quite interested that the three tie bar fixings (steering box to panhard rod) were initially nipped up to 80Nm and then loosened 'one full turn' - which given that it was not a fine pitch thread on those fixings was essentially 'loose'. You do the road test and then nip them up again to 110Nm and 80Nm once things have settled.

I like to try and follow the manual where I can - gives me a little confidence that I'm keeping my numpty tendencies in check! 

(Edited to add 'no offence intended') 

Edited by Northwards
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