Power steering gurus required

My project has ground to a halt due to failed steering. We rebuilt my car using, my rack and PAS pump. We added a NSF air to oil cooler under the head light mounted to the chassis leg. The system bled as per instructions. The rack performed well for about 300 hundred miles of testing and mapping. Suddenly the pump started to make a noise, which rapidly got worse. We got hold of a pump from a runner. This pump made a noise right from the start, now we have no power steering at all.

We are a bit stuck now, we could strip the pump and check all the specs and replace parts as necessary. However the second pump had never been subject to the 8500rpm of my original, but still howled in protest at tick over and above. The system was bled but the noise would not go away. I see two possible causes for the problem, one being higher pressure on the system than it was designed to take, the other higher temperature fluid round the system. As yet we have not tried to test temperatures in the fluid. Now with no pump action, getting a temperature readings is going to be difficult. If we assume the second pump was OK, then what could cause the pump to howl right from the start?

I have been away, so the car was not run for a few days, one of my sons had to move it, this is when the steering failed. Any input to this problem would be much appreciated, it is so frustrating having a beast of a car that can not be driven.

a NSF air to oil cooler

This and the extra plumbing, possible restriction/airlock which has caused the problem? You wouldn't expect the pump to last only 300 miles with the increased load on it.

When you go single is the increased speed or the increased acceleration of the pump likely to cause problems? Is it possible to dispense with the cooler and increase the size of the power steering pulley and fit a larger belt. I suppose this depends on how exactly the Supra varies the assistance relative to speed if you want to keep this the same as a stock car.

Subscribed, I have a modified powersteering system with -10AN lines and a oil cooler, the cars off road just now, just hope I dont have this same problem,

My lines arent as long as yours though, but it shouldnt really matter, the pump should be capable of pumping power steering fluid around your cooling system

Could the Oil cooler be the restriction?

Are you using underdrive pulleys?

Have you changed the reservoir for a new, unpolished, unadulterated one, IE it could be debris in the filter that's within the reservoir? Could be a suction side air leak on the lines to the reservoir or pump. Could be a goosed rack.

Reach down inside the resevoir with a flat blade screw driver and scrape it across the mesh/filter gently. Pull it up carefully and see if there's much cack on it....as Chris said the filter (which is not removable) could be blocked.

Edit: If it is then a new resevoir would be a sensible purchase.

Thanks for the input, food for thought. I will carry out the simple tests this morning. Perhaps over the short period of time the car has been rebuilt any air sucked in has collected in the cooler. If this is so, then air collected in it, has made a compressible air bubble that would getting bigger and bigger until the system could not pressurise properly. That would certainly explain why a replacement pump made absolutely no difference, and we have no steering at all now, as the air introduced by fitting a pump has also gathered in the cooler. I know this is just theory but it all fits the symptoms and speed of onset.

It's not air bubble, it'll be the pump, the feed from the reservoir or the rack itself, unless you have crushed a pipe when doing engine work.

All sorted. The feed pipe to the pump goes under the new plenum. The hose had a slight kink which was suck closed when the pump was under demand. Temporary fix was to shorten the hose so that the kink was pulled tight to prevent the hose from collapsing. New stiffer walled hose being delivered tonight. System bled after two steering cycles, steering back to normal.

Thanks for the advice.

Nice one.

So would the old pump have been ok?

No worries.