Power Steering - air in the system?

[SPendrey]

Firstly, this is an issue on a 1994 Disco, but I figured the power steering is the same on Defenders too?

So, starting up in the morning I get a couple of seconds of heavy (no) power steering, but after a few revs and/or metres travelled all seems to be fine.  Very rarely, later in the day (after work), I'll get the same for just a second or so.  Would this be symptomatic of air in the system?  I'm imagining as the pump develops pressure, that air is compressed to the point of not making much difference.

The pump itself is a fairly new (cheap Chinese) thing, and the steering box is a 2 year old recon unit... so neither can be 100% relied upon, but they've been doing a good job so far.

I suppose belt slippage would also cause this sort of symptom, will check the tensioner.  But, I don't see why that would only happen at the start of the day.

Regards,

Scott

[=jon=]

Air in the system manifested itself on mine as 'lumpy' steering - turning from lock to lock wasn't smooth. 

A few turns of lock to lock back and forth and 15 mins driving round and it bled itself. 

Maybe belt is slipping a bit after the stress on the system of starting up / increased draw on alternator / all fluids cold etc... 

[Maverik]

Belt slip or your PAS pump is on its way out.

[SPendrey]

Can't be 100% sure yet, but I forced child #2 to sit in the cab turning left/right while I bled the steering box back into the reservoir (fluid is fairly new).  Didn't see anything untoward, but doing this seems to have stopped the heavyness.  At the same time, I noticed the front left tyre was deflated slightly, so pumped that up (from ~18 to ~30psi).  That probably helps too.