What would cause my power steering fluid to boil?

[oz]

What would cause my power steering fluid to boil over?

I had my steering pump, valve and ram rebuilt recently (when I had the engine out of the car...), replaced all the hoses and fluid.

A couple of times since I got the car running again, after long periods of high speed idling, it looks like the pump has shot boiling hot steering fluid out of the filler hole. I have not witnessed the purge but the placement of the oil makes me think it's coming out the top (its on the valve cover, headers, back of the pump, etc). The fluid level is correct and I have cycled the steering side to side to purge any air but the fluid still gets super hot.

Later in the day - after the most recent fluid purge and cleanup, I started the car up to put it in the garage and it left a regular drip trail in the driveway as if the high pressure hose was leaking at the connection near the bottom (there was no fluid up high, only on the hoses). I cleaned up everything and wrapped rags around the lower hoses and over the filler cap. I drove it around the block (after it was cool) and there was no oil on any of the rags.

In the past, when the wheels were off the ground and turned a little, if I started the car and the wheels would turn to full lock. Not always in one direction. They go in whatever direction the wheels are turned at the time.

Does anybody have any ideas or suggestions?

 

[reenmachine]

In the past, when the wheels were off the ground and turned a little, if I started the car and the wheels would turn to full lock. Not always in one direction. They go in whatever direction the wheels are turned at the time.

Perhaps a screw-up during the rebuild of the control valve? It looks at the steering input direction and gives assist in the same direction. Perhaps the internals are sticking, and when you're driving down the road in a straight line you're actually fighting it a bit, heating the fluid.

Anyway, if there's a restriction that shouldn't be there, the added friction will heat the fluid.

 

[mustangdave]

It could be the rebuild. Try recentering the control valve centering spring.
Raise the car and remove the two screws and lock washers and remove the spring cap.
Tighten the adjusting nut snug; then loosen the nut 1/4 turn.
Put the cap, screws, and washers back on.
If this doesn't work, the only other thing I can rhink of is the valve is not installed the right distance onto the center link.Let me know if you need that procedure and the measurements.

 

[oz]

I will try the centering adjustment. Please see your PM mustangdave.

As far as the valve being positioned wrong to the link - if it means anything, everything lined up and the steering wheel was straight after the rebuild. I will check the turns lock to lock (wouldn't that tell me if it's off)?

Thanks!

 

[ron67fb]

In the past, when the wheels were off the ground and turned a little, if I started the car and the wheels would turn to full lock. Not always in one direction. They go in whatever direction the wheels are turned at the time.

This means the lines at the control valve are reversed. They're the same fitting so it's easy to mix them up.

 

[reenmachine]

This means the lines at the control valve are reversed. They're the same fitting so it's easy to mix them up.

It's been my understanding that when the lines are reversed you get violent oscillation back and forth, and the car wouldn't be driveable like it apparently is.

 

[oz]

Car drives very well... I don't have to rock the wheel back and forth anymore to keep it going in a straight line (had the gear rebuilt too). The steering effort is pretty low too.
The only thing that has gone wrong is that the fluid seems excessively hot and the pump spit fluid out the top (and maybe from a hose... not sure yet though) after sitting and idling for awhile.
The service manual says the steering oil temp should be ~175F so I will check that.
The working pressure of the pump is 750 psi acording to the manual so if I had a leak in the lines, I think I would know right away.
I will keep investigating.
THANKS!

 

[thehueypilot]

Sounds like it could be air still in the system. With air in the system you would have less fluid causing the higher temp. The air would work its way out, but would shoot out the vent hole when it arrives back into the pump reservoir taking some fluid with it. Just a hunch....

 

[oz]

What's the best way to correct this if this is the case?
Just Saturday I jacked up the front of the car, started it and turned the wheel lock to lock a few times (after the oil was spit out)... I had not done that since the rebuild.
I may try to recreate the problem again before I go any deeper in case there was air in the system.

Thanks.

 

[thehueypilot]

What's the best way to correct this if this is the case?
Just Saturday I jacked up the front of the car, started it and turned the wheel lock to lock a few times (after the oil was spit out)... I had not done that since the rebuild.
I may try to recreate the problem again before I go any deeper in case there was air in the system.

Thanks.

To get air out of a hydraulic system you need to bleed it from the highest point in the system but with pressure on it. Somestimes air gets trapped in places that is not the highest point so then you must try to bleed it as close to that point as possible with pressure on it. It's like bleeding your brakes but you don't want to crack open a fitting very much. If you crack it open and it hisses at you you know you stuck air.

 

[reenmachine]

To get air out of a hydraulic system you need to bleed it from the highest point in the system but with pressure on it. Somestimes air gets trapped in places that is not the highest point so then you must try to bleed it as close to that point as possible with pressure on it.

Isn't that why the pump is the highest point in the system -- so you don't have to crack a line to bleed it? Since the fluid circulates (unlike brakes), wouldn't air bubbles find their way back to the reservoir once the system is run through its full range of motion several times?

 

[oz]

I checked the car again last night and now fluid is leaking out the front of the pump - around the edge where the reservoir meets the pump. It did not leak here for ~8 months and now it does.... I think this is a result of the other problem (excess pressure and temprature maybe).
I'm going to call Harry's Steering Gear today and find out what they (or I) can do about this since they did the work and I never had any problems with the pump or valve before.

Update: Called Harry's and he said to bring in the pump and valve and they would look at them again...

 

[ron67fb]

It's been my understanding that when the lines are reversed you get violent oscillation back and forth, and the car wouldn't be driveable like it apparently is.

<shrug> I just remember that before the server crash there were a few threads about cars steering themselves, and turned out that their connections were reversed. No experience with it myself.

 

[thehueypilot]

Isn't that why the pump is the highest point in the system -- so you don't have to crack a line to bleed it? Since the fluid circulates (unlike brakes), wouldn't air bubbles find their way back to the reservoir once the system is run through its full range of motion several times?

Yes you are correct, but if you have an air pocket that you can't seem to get out I would try to help it along with this method.