c3 power steering

[William S.]

I just changed the PS control valve and hoses in my 1969 350/300 to repair a leak. Steering was fine before changing the unit. Now while driving the wheel occasionally jerks in my hand and it feels as if the car is trying to turn. Seems to happen on acceleration, although it also sometimes also seems to happen at constant speed. It's a fairly subtle jerking and at first I though I was imagining it because the steering was a lot lighter with the new control valve.

I adjusted the valve as described in the service manual. I've examined the front steering components and don't see any other issues. The car corners fine and steers fine most of the time.

Could a defective control valve do this? Is it possible that changing the control valve surfaced an issue in the pump or power cylinder? Can I remove the power steering belt and drive the car to see if it eliminates the problem? I think the issue has to be power steering related. Any advice greatly appreciated.

[Timothy B.]

Re: c3 power steering

William,

The one suggestion that comes to mind is to make sure the system is purged from air first then adjust (center) the valve null position.

[Joe L.]

Re: c3 power steering

I just changed the PS control valve and hoses in my 1969 350/300 to repair a leak. Steering was fine before changing the unit. Now while driving the wheel occasionally jerks in my hand and it feels as if the car is trying to turn. Seems to happen on acceleration, although it also sometimes also seems to happen at constant speed. It's a fairly subtle jerking and at first I though I was imagining it because the steering was a lot lighter with the new control valve.

I adjusted the valve as described in the service manual. I've examined the front steering components and don't see any other issues. The car corners fine and steers fine most of the time.

Could a defective control valve do this? Is it possible that changing the control valve surfaced an issue in the pump or power cylinder? Can I remove the power steering belt and drive the car to see if it eliminates the problem? I think the issue has to be power steering related. Any advice greatly appreciated.

William------

As Timothy mentions, the problem could be that all of the air has not been bled out of the system. Did you follow the procedure in the service manual?

Most likely, though, the problem is with the control valve. It might not be defective but, as Timothy also mentions, it might not be centered properly. The best way to center these valves is on an hydraulic test bench. Of course, you won't have one or, likely, even have access to one. The valve rebuilder or manufacturer should have done this for you. I have found that centering the valve on the car can be much more difficult in practice than the service manual implies.

One more thing: do you know the manufacturing source of the valve you have? I understand that inferior Chinese-manufactured valves are on the market these days.

[Edward J.]

Re: c3 power steering

Bill, Tim's idea is a good one, also add to the mix make sure the front wheels are off the ground when making the adjustment.

[William S.]

Re: c3 power steering

I didn't follow the bleeding procedure carefully. I'll try that. The control valve didn't seem too far out of balance. Following the procedure required very little adjustment. I bought the valve from Paragon. They had two new options, one with the parts made overseas and assembled here, which was several months on back order. I bought the one made and assembled overseas because I didn't want to wait. They told me they haven't had any issues with the valves. I've bought a lot of parts there and never had a problem before so I went ahead and got it. Should probably have done some more research before buying. Anybody have any recommendations on a source?

[William S.]

Re: c3 power steering

I think this was a coincidence. I bled the system and couldn't replicate the problem with the front wheels in the air but it still happened when driving. I had examined the entire steering and front suspension when it first happened so today I took off the rear wheels and looked at the rear suspension. One of the trailing arm bushings has disintegrated and is just about gone. I think what I was feeling on acceleration was a shimmy in the rear. The fact that I had just changed the control valve threw me off because I figured that had to be it. Now that I think about it, but problem didn't occur until about a half hour into my first test drive and I was feeling the car swerve rather than the wheel jerk. Thanks for all the good suggestions.

[Edward J.]

Re: c3 power steering

[QUOTE=Joe Lucia (12484).

One more thing: do you know the manufacturing source of the valve you have? I understand that inferior Chinese-manufactured valves are on the market these days.[/QUOTE]

Joe I just installed my first new one for a cust. and it was from Lonestar, and as you say they are in trail stages right now, Any way mine had a small leak. from what I understand there is a shortage of original valves for rebuilding.

[Joe L.]

Re: c3 power steering

I think this was a coincidence. I bled the system and couldn't replicate the problem with the front wheels in the air but it still happened when driving. I had examined the entire steering and front suspension when it first happened so today I took off the rear wheels and looked at the rear suspension. One of the trailing arm bushings has disintegrated and is just about gone. I think what I was feeling on acceleration was a shimmy in the rear. The fact that I had just changed the control valve threw me off because I figured that had to be it. Now that I think about it, but problem didn't occur until about a half hour into my first test drive and I was feeling the car swerve rather than the wheel jerk. Thanks for all the good suggestions.

William-------

Failure of the forward trailing arm bushings can produce the symptoms you describe. However, it does seem highly coincidental that this should happen right at the same time you replaced the power steering parts.

[William S.]

Re: c3 power steering

Hi Joe,

Completely agree. My plan is to change the bushings and do another test drive to see. Given all of the symptoms though, and the fact that I couldn't replicate it with the front wheels in the air, I'm thinking it's a big coincidence. We'll see. Thanks again for your help.

[D S.]

Re: c3 power steering

And don't put your arm inside the steering wheel to start it off the ground.

[William S.]

Re: c3 power steering

William-------

Failure of the forward trailing arm bushings can produce the symptoms you describe. However, it does seem highly coincidental that this should happen right at the same time you replaced the power steering parts.

Rear bushings are completely gone on both sides so I think this will do it. I have a follow-up question. I've taken out the bearings on one side and cleaned them off. They look fine. No discoloration and they spin freely. I'm assuming that once I assemble the unit and the play is within tolerance then the bearings are fine. Is there any other test on them I should do? They aren't that old and I didn't have any problems until the bushings went but I'd hate to put this all back together and find out I had another problem.

[Joe L.]

Re: c3 power steering

Rear bushings are completely gone on both sides so I think this will do it. I have a follow-up question. I've taken out the bearings on one side and cleaned them off. They look fine. No discoloration and they spin freely. I'm assuming that once I assemble the unit and the play is within tolerance then the bearings are fine. Is there any other test on them I should do? They aren't that old and I didn't have any problems until the bushings went but I'd hate to put this all back together and find out I had another problem.

William------

There is no other test I know of for the bearings. As far as REAR wheel bearings go, it's rather difficult to access them for inspection. So, my plan is always to replace the bearings whenever I have them out for any reason, even if they have low mileage on them. However, this is just my approach which, admittedly, may be overkill.