Power steering fluid pressure

I have just got my car back after having the entire suspension front and rear overhauled, every single bush was replaced including the front sub frame V block mounts and the circular rear mounting bushes.The springs and pans were powder coated along with the wishbones and roll bar, new shocks were fitted all round and both subframes painted. The front sub frame was removed from the car during this process along with the steering rack so the power steering system had to be drained. The car feels fantastic to drive but I’m not sure if I have a problem or not with the power steering system.
When I arrived home after the 120 mile journey from the workshop I removed the cap on the power steering resevoir just to check the level and quite a lot of fluid spewed out. Thinking it was just over filled I syringed some off until the level was just above the white screen and level with the ’ Max ’ mark. I’ve been keeping a check on the level for the past week and it has remained at this level, but when I remove the cap following a drive and everything is hot there is a residual pressure, it hisses like when removing a radiator cap and I can hear a gurgling noise. In the past I’ve only ever checked the fluid level when the car is cold so I’m not sure if this is a problem or not ? The steering feels great when driving and there are no leaks, am I worrying about something that is normal ?

Any signs of water/coolant in your PS fluid, or signs of PS fluid in your engine coolant reservoir?

Hi Mike, no there is no sign of coolant in the PS fluid, or of PS fluid in the coolant. Just a long hiss and gurgling noise when I remove the PS filler cap. The fluid level is remaining constant at the correct level too.

Try leaving the removal until the PS is cold and see if the condition (pressure) is still apparent.

Hi Robin, there is no pressure or gurgling noise if I leave the car to cool down for half an hour or so. I have been checking it immediately after each period of driving just to be sure I hadn’t removed too much fluid and that’s why I noticed it. In the past I’ve only ever removed that cap when everything was cold so I’m not sure if it’s even a problem and maybe they all do that when the fluid is hot ?

Maybe there’s an airlock? Try opening the cap and turning the wheel lock to lock a few times them have a look at the level?

The fluid expands when heated and the cap needs to seal. Never overfill the reservoir and don’t open it while the fluid is hot and if everything else works, you’re fine.

You’ll hear it if the level is too low.


Thanks for the explanation David. That makes sense to me now. If the fluid expands when hot it must create a small pressure in the space below the filler cap and that is what I’ve been hearing when removing it with the fluid still hot.