Power steering fluid leaking from cap

[AceOfHearts]

The power steering fluid on my Jaguar keeps leaking from the vent at the top of the reservoir cap. I have just been and tested it whilst parked up to watch what it is doing, and it seems to be that when you turn the wheel and stop it suddenly, there is a little puff of oil mist coming from the breather at the top of the cap.

The fluid loss is minor, but it is covering that half of the engine bay

Any idea?

[Jimmyarm]

How full is the resevoir ? It should only be up to the max mark at highest, any higher and you will get some leakage until the level drops back down.

Assuming the level is correct, there is probably an issue with the rack allowing the high pressure to be released straight back into the resevoir along the low pressure side (causing the big spurter ) Or possibly the non return valve has failed allowing the pressure to shoot back up through the pump.

Not 100% familiar with the Jaguar system but has it had any work done recently ? The Fords of that era have a little valve in the end of the pipe on the rack that can be put in the wrong way round/not at all.

[AceOfHearts]

It had the engine replaced late last year

The fluid level is fine, as the reason I noticed it was that the engine bay was covered in oil and the power steering fluid was low.

The one way valve does sound suspect. I don't know the system particularly well either and the internet doesn't seem to have much detail on it, I will have to dig around the parts manual later and see if it shows anything.

If it is the rack then that isn't too bad a job as i wanted to remove it at some point anyways to polybush the mounts as they seem very slack. I don't want to get lured in to replacing bits willy nilly though before I fully understand what the issue is.

[oakdale]

This kind of problem is usually caused by tiny air bubbles in the fluid.

Check the joints on the low pressure hose between the reservoir and the pump.

[AceOfHearts]

Thanks guys, I have checked the hoses but cannot see anything obvious, but i have since done a couple of fluid flushes with some high quality power steering fluid and seems to have almost totally fixed the problem.

All there is now is a tiny weep from around the cap but I can't see any mess on top from it jetting out any more and the level hasn't dropped in 200 miles. Maybe it was a sticking valve or some air trapped in the system which changing the fluid has fixed?