Ok, so I replaced the power steering pump about a year ago (because it was groaning). It worked fine for a few months, but started leaking. Exchanged it under warranty, and the new one has been fine for a few months, but all of a suddend I have no power assist.

I took the '75 for a nice long freeway cruise this weekend. It was fine all the way there. Then, it was fine all the way home. Dropped a buddy off, then got back on the freeway to go home. When I got off the freeway, I didn't have any power assist. Once I got moving it turned ok (but just like a car with no p/s, it turns much easier when moving). It was like that the next couple of miles until I got home. I checked the fluid, and it was right at the low mark, so I topped it off. Started the car, and still no power assist. A little later I tried again, and at idle, no power assist, but if I reved the engine a little it came back.
So ok, it sounds like the pump is bad. But then today, I started it up, and everything seems back to normal. I took it out for a short spin around the neighborhood, and it was find.

So what's the deal? Could the pump just be failing, and it's working now, but will quit again? Or could that happen? When the pump goes bad, does it go bad all at once? or maybe the valve got stuck? Any ideas?

Yes, I did a search, but I couldn't find exactly what I was looking for.

Thanks!

 

The only power steering pump that failed for me had a bearing go out. I think that's the most common type of failure.

You didn't mention that it was making any noise so I doubt that is the problem. I was just wondering if there is some reason that the belt isn't turning the pump. Maybe the pump has loosened and the belt is loose or possibly the pulley is spinning on the shaft. I don't know how the pulley is attached on the Vettes but some pulleys are just pressed on an some are held on with a bolt. I guess it is possible that something is loose. At least it's something you can check.

 

Could this valve be stuck?

 

Did you check the oil level in the steering pump?

 

It sure seems that losing power steering fluid and the lack of assist problem are related. First determine where you are losing fluid. Also when you lose assist, peak into the pump reservoir. Is the fluid clear or milky in color? A milky colored fluid would indicate air has entered the system and your are feeling the lack of assist because the fluid has millions of tiny bubbles circulating in the system.

It is possible that the low pressure (return line) side of the system can be sucking air into the system as the fluid circulates. Then fluid drips out when your engine is off.

It is possible that your lack of assist can be a stuck flow control valve as shown in the picture above. Remove the discharge fitting. Reach into the pump cavity and press on the valve. You should be able to depress the valve against the spring. It should easily slide in the pump bore and not feel sticky. But a sticky valve would not explain the fluid leak.

Jim

 

So I'm not losing fluid, and I've driven the car to work two days in a row (22 miles each way) with no loss of power assist... so I guess a valve got stuck somewhere... then unstuck...

I guess I'll just drive it until it goes out again.

 

Keep Jim Shea's input in the back of your mind. If this happens again, it is very possible that your problem is as Jim describes. If the return line is allowing air to mix with the fluid, it will eventually foam up and will no longer be "incompressible", thus preventing proper operation. After the fluid sits for several hours, the foaming subsides and the unit will again work OK (for a while). If this is actually occurring, a longer trip will yield another P/S failure.