Classic/Antique Car Repair: 1967 Mustang Power Steering, friction modifiers, automatic transmission fluid

Question
Recently I rebuilt a 1967 Mustang with a 390 cu in engine.  I replaced all the power steering components and the system worked great.  However, the pump had a small drip at the bottom of the reservoir so I replaced the pump.  As I was running a few miles with the new pump the power steering fluid (Type FA) leaked all over the engine compartment (through the filler tube).  Assuming the the pump was defective I replaced the pump again.  Once again the 2nd pump seemed ok until I put on some additional miles at a higher RPM, then boil over again.  When the car is running the steering is good with no problems turning.  I am not sure what went wrong since the car was running great until I replaced the pump.  Any sujestions on what to check or tips on reinstalling this particular pump?

Thanks,
Pat

Answer
I think there are two possible causes for all this. #1 is that I don't think you are using the right fluid. You mention power steering fluid, but I think you are putting type F fluid in there, but that has friction modifiers and was never intended for use in anything other than the few Ford transmissions that specify it.

So, step one is to get all that fluid out of there. You can use Dexron-Mercon automatic transmission fluid in your power steering pump.  But flush all the type F out of there by removing the return hose from the pump and then lower it to the ground and let it drain into a pan overnight.  You can start the engine briefly to expel the last bit of fluid by turning the wheels to both stops a couple of times, but don't run the engine for more than a minute or so!  Better yet, take the belt off the pump and turn it clockwise by hand until you expel all the oil.

Now, refill the system with Dexron-Mercon fluid and after you've filled it, start the engine and again, work the wheels back and forth a few times to expel all the air from the system - I think that is probably problem #2- there was some air trapped in the system.  You will have to keep topping up the fluid until all the air is gone.

If you have the old pump (the one with the drip at the bottom), you can fix it by replacing the large "O" ring that seals the reservoir can to the casting, and keep it as a spare - you know it's a good pump, and you can put it back on if the "new" ones (which were rebuilt in some dusty workshop in the poor end of town) continue to give trouble.  The "O" ring is a 50 cent part.

I hope this solves your problem - if not, let me know!

Dick