isosceles

When I drive the car at highway speed, RPM over 2500 for a few minutes or above 3000 for a shorter time, the power steering assist doesn't seem to work when I slow for a turn. After the first turn, it seems to be fine when I try to turn the wheel for the next turn.

I installed a new control valve Monday evening. Last night I made sure to bleed the system of air with the cap off the pump, front wheels off the ground, turned from lock to lock several times, some at idle, some at 1500RPM.
What could be the cause?

Matt Gruber

did the old control valve do the same thing?

isosceles

Matt,
No, the old control valve leaked, so I replaced it. There was also some play in the old one that is not present in the new one. I also replaced the pump about 2 months ago. Could the suction hose be collapsing at higher RPM? If so, can I used transmission cooler hose for that? I have a bunch of it at home.

Matt Gruber

someideas
1. idle too low
2. belt slipping
3. hose near exhaust boils fluid
4. low fluid
5. dirt in valve

Jim Shea

Just to get the terminology correct. First I assume that you have a production power steering system, (i.e. power steering pump with a reservoir attached directly on the pump, hoses, control valve, assist cylinder, & manual gear). Therefore, the low pressure 3/8 inch ID hose coming from the control valve back to the power steering pump reservoir is a typically called a power steering return line hose.

If you have a special power steering pump with a remote reservoir. There is typically a 5/8 inch ID hose that feeds from the remote reservoir back to a 5/8 inch OD tube that is part of the pump. A large ID hose is required so that the pump intake isn't "starved" for fluid.

Typically the 3/8 inch ID return line hose doesn't collapse and cause restriction. The fluid coming from the control valve will "push" its way back and open the hose. However, it is possible a return line hose to be incorrectly routed so that it could be severely kinked and therefore it might restrict flow.

If you had a remote reservoir, then it is sometimes possible for a 5/8 suction hose to collapse because the pump is trying to draw a large quantity of fluid back into the pump intake. A power steering 5/8 suction hose should be designed to withstand low pressure suction forces.

Now back to your problem. When you experience a lack of assist, do you note that the pump is making more noise than usual? Also, have you checked to see if the fluid appears milky? A milky appearance is caused by air that has been whipped into the very small bubbles as it passes through the pump.

If there was any air left in the system, driving your car about 10 miles and leaving it sit overnight is usually enough time for all of rest of the air to work itself out.

Are your return line connections secure? It is possible for a low pressure return line connection to actually suck air into the system even though it may not leak air out!

Keep posting if you continue to have a problem.

isosceles

Thanks guys. Jim, I have a stock setup on the P/S. It's weird, I encountered the problem this morning, but not on the way home, AND not on the way to or home from the track tonight.
I do have new cylinder hoses to install as the flare fittings seep slightly on the old ones.

I'll re-bleed it after I install the new hoses, but am leaving them alone for now. Thanks for the tips! :yesnod: