Power steering overrun - lack of flow or worn box?

[hal9000]

I've had an electric power steering pump on the car for about 3 years, info about it here.

It has been just fine for around town driving and parking lot work. If you are turning the wheel fast, it seems to be easy to overrun the pump and lose assist. I took the car to an autocross last weekend and the power steering was effectively useless. Every time there was a fast transition, assist was gone. I assume this was because I was moving the box piston faster then the pump could flow. What I'd like to try to understand is if this is a lack of flow symptom, or a warn out, 55 year old, steering box issue which now has a lot of internal bypass going on in the control servo valve.

I don't have enough experience with PS box's to understand if this is a common thing, and I don't have the flow number on a factory pump vs my pump to know if I'm way off etc. I can rock the the wheel side to side and easily find the limits with the current setup, I'm really hoping it's the box.... I don't have a factory pump to put on there anyway to test. (magnum swapped car), but I may just have to try that before replacing the box.

When I got the car, it was being driven with no pump on a power box, so I have no idea if the box worked well then, it alwasy just had lots of play until I put the electric pump on it.

Thanks all for your thoughts.

 

[chrgdrt]

I used to run into that problem in my 68 that had the federal pump. I currently have a 67 that I converted to ps using a Saginaw pump and have not had that problem so I’m going to say it’s a pump problem, not enough flow.

 

[hal9000]

Just for anyone who runs across this. The pump I'm using is the problem, not enough flow. I hooked a flow meter up to it and it runs 1 GPM in it's limp mode, so, it's just fine for around town driving, but no good for racing / autocrossing. It looks like you need at least 2 to 2.5 GPM for the borgeson box, and I suspect more for the OEM box.

 

[Kern Dog]

I used to run into that problem in my 68 that had the federal pump. I currently have a 67 that I converted to ps using a Saginaw pump and have not had that problem so I’m going to say it’s a pump problem, not enough flow.

I agree with this.
What also helps is to add an inline cooler like this:

This one I mounted on the frame rail below the battery tray.