Power Steering Leaks

#1
Well, not exactly 'leaks' but does overflow through the filler cap. Here is the situation: I fitted a power steering box from a 3500S into my highly modified 2000TC, coupling the box to a Saginaw pump/reservoir unit (so called 'Ham Can'). The limited real estate under the bonnet, with the Ford 302 V8 taking up a lot of space, dictated the position of the pump relative to the steering box. The reservoir, therefore, is a couple of inches below the box return fitting.

Today I started the car after it had been sitting for a week or so, and noticed a lot of fluid coming out of the top of the reservoir, past the filler cap. And the power steering wasn't working, probably because all the fluid had drained out of the box, down into the reservoir. So my question is this: have I designed in a fundamental flaw by placing the reservoir below the box? Or is there something else going on that I don't understand about the system?

Originally I had a remote reservoir (salvaged from a Jaguar Mk2) and it was placed higher than the steering box. This system used a separate pump with no integral reservoir and all seemed to work well. But the pump failed and I decided to 'neaten up' the engine compartment by going to the combination pump/reservoir. If necessary I will return to the remote reservoir scheme but before I do I would like to understand the system better and what I'm doing wrong. Any help would be greatly appreciated.

Cheers,
Tom
 

corazon

Well-Known Member
#2
Is the pump pressure too high?
I'm planning on using an adjustable valve, Heidts make one, which allows you to tune the feel of your power steering by bleeding off some pressure back to the return pipe.
Mine will have a hydroboost brake booster which works from the power steering pump, and this means full power can go to the brakes and less to the steering box..
Jim
 

colnerov

Well-Known Member
#3
Hi, Tom. Everything you say is right, I think that is exactly what is happening. You need
to go back to the higher remote reservoir system. Nice try though!

Colin
 
#4
colnerov said:
Hi, Tom. Everything you say is right, I think that is exactly what is happening. You need
to go back to the higher remote reservoir system. Nice try though!

Colin
Colin,

Yes, I'm afraid you are right and that I screwed this one up. But I'm wondering if some sort of anti-drain back valve might work if inserted in the return line? Something along the lines of the anti-drain valves used in oil filters to prevent them from draining dry when the motor isn't running.

Tom
 
#5
corazon said:
Is the pump pressure too high?
I'm planning on using an adjustable valve, Heidts make one, which allows you to tune the feel of your power steering by bleeding off some pressure back to the return pipe.
Mine will have a hydroboost brake booster which works from the power steering pump, and this means full power can go to the brakes and less to the steering box..
Jim
HI Jim,
I set the pressure as low as the pump would allow, namely 750 psi. The Rover box is said to operate at 850 psi but because it is old and hasn't been rebuilt, I was afraid of blowing seals. Also I wanted to reduce the power assist to get more road feel. Seems to be ok in that regard, ok that is, when there is actually fluid in the system and it hasn't drained out all over the road and my garage floor :)

Tom
 

colnerov

Well-Known Member
#6
Hi, unfortunately Tom, oil is supposed to return to the reservoir so anti-drain valves
are not a good idea! If you can used a sealed cap on the reservoir with a small bore
breather pipe going from it to above the level of the steering box that may stop the
mess. However you would have to run the motor up before checking the level, and
thinking about it you may get notchiness and hydraulic whine every time on first
start up because of the introduced air.

Colin
 
#7
colnerov said:
Hi, unfortunately Tom, oil is supposed to return to the reservoir so anti-drain valves
are not a good idea! If you can used a sealed cap on the reservoir with a small bore
breather pipe going from it to above the level of the steering box that may stop the
mess. However you would have to run the motor up before checking the level, and
thinking about it you may get notchiness and hydraulic whine every time on first
start up because of the introduced air.

Colin
Hi Colin,
the type of valve I was thinking about opens at around 2 psi so it would prevent drain back while the engine is off but should open when the box gets some pressure. But it is looking like the best route is simply to go back to the remote reservoir that I had mounted higher than the pump. That setup worked well and I should have left it in place.
Cheers,
Tom
 

unstable load

Well-Known Member
#8
You could try extendng the return inside the tank to a point whare it's below the lowest possible level the oil will reach.
That way, no air can migrate up the line to allow the oil to drain back.
 
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