Power Steering Pump Failure?

[jemram]

Hi Guys,

My first post on here, but I've got a few post on the UK forum.

I have a problem with my Power Steering on my 1991 LS400. When the start the engine from cold it's fine, but as the engine warms up and the idle settles to a warm idle of around 650rpm my power steering becomes very heavy, as heavy as when the engine is switched off. If I increase the engine speed to 1000rpm again it's fine, and it's fine when the car is moving at anything above walking pace.

I've removed and cleaned the strainer on the soloniod on the steering rack and also changed the fluid to fresh DexronIII, but it's still the same.

I'm guessing the only option now is to change the pump?

Many thanks in advance.

[larryp]

Probably the pump but could also be the air control valve on the pump. It is designed to give a "boost" to the steering at low rpms. However, when mine went bad (starts sucking PS fluid into the intake and exhaust billows thick white smoke), i just pugged it and ran without it and had no problems with steering at low idle.

[wwest]

Probably the pump but could also be the air control valve on the pump. It is designed to give a "boost" to the steering at low rpms. However, when mine went bad (starts sucking PS fluid into the intake and exhaust billows thick white smoke), i just pugged it and ran without it and had no problems with steering at low idle.

"....designed to..."

Power stearing pumps are traditionally a horrible waste of HP, they are constant displacement pumps with a spring relief valve to releave excess press/flow back into the sump. Cruising along a 55MPH the is little need for this pumping effort so virtually all the "work" is needless. Normally the air control valve reduces the level of pressure the pump must provide as roadspeed increases. Apparently yours has failed in the "cruising", low pressure, mode.