Vikefan88

Hi everyone. I’m going crazy. I’ve read almost all the forums, but I need help. 65 mustang v8 with bendix power steering. I replaced the control valve with a rebuilt one, all new hoses. It no longer leaks. But the steering goes crazy from end to end. Is it getting rid of the air? See my video.


https://youtu.be/br7Fey02vB4

Gun Jam

so it was fine before the control valve replacement?

Just by looking that really seems to indicate a valve issue. I would contact the seller of the valve.

Vikefan88

yea, it worked great. Just leaked...

Gun Jam

Right... I remember those days. The valve is responsible for feeback if I recall correct. Perhaps its built wrong or there is a faulty part in in. There isnt much else that I can think of that would induce a turn like that. i know little about them but the phrase "a ****ed up servo" is likley correct. or whatever its got that acts like a servo.
-Gun

imp

Original 65 PS used a control valve mounted integrally with the idler arm. The valve was spring-centered; During straight-ahead driving, the valve directed pressure to both sides of the PS cylinder at the same time, providing added guidance control. When the valve was off-centered as in turning in a parking lot, that added more pressure to the appropriate side of the cyl. piston, adding power assist. During taking curves at speed, the spring within the valve was too stiff to add any assist. It was a PRESSURE_BALANCED system.

A broken or misadjusted spring allowed oil pressure to be present where it did not belong, under given driving conditions. This could range all the way from an oscillating back and forth to the video condition above. Such oscillation happened on mine occasionally at road speed; It was scary, but did not jerk the wheel from my hands. It kind of "wiggled" side to side about once a second. Kicking the brake pedal stopped it. Such occurrence is is called POSITIVE FEEDBACK.
;

Vikefan88

so you recommend trying to adjust the spring to center?

Vikefan88

imp

The valve spool is centered by a single spring, as I recall (it's been maybe 40 years now since I had one apart). One direction of movement compresses the spring, allowing hydraulic assist to one side; other direction depresses valve against hydraulic pressure, but allows power assist to other wheel. There is a specific travel called out for the valve, it is quite small, maybe < 1/4" total, 1/8" either direction. Since it's centering is mechanically determined, location is automatic. What CAN happen is the spring loses tension over time, or breaks, rendering the valve position indeterminate: may steer either way, or not at all. Sludge build-up can be a problem. The valve spool itself is typical of any spool valve, like found in transmission valve bodies. Spools sometimes jam, an added problem. Seals effectively prevent oil from entering the spring chamber, which is located at one end of the valve body, enclosed by a 2-screw hollow cap. The adjusting nut for spring tension is located within this cap.

Why is this system worth a ****? When power assist is not needed, as driving straight ahead, or turning non-demanding paths on highway, pressure is directed to BOTH sides of the power piston, enclosed in a separate tube, which "locks" the wheels together turn-wise, stabilizing steering control. Only when steering effort is great enough (as in parking) does the valve off-center to provide assist.

Your question: Centering of the valve is basically mechanical. The spring tension only maintains the valve at one stop of it's travel. A front-end hit can damage the valve's ability to move properly, heat check may have weakened the spring, or it may be broken. Higher spring tension means later PS "kick-in", and vice-versa.

Whew! imp