1968 Continental Power Steering Issues

Hi Bill –
I found your blog and that you’ve helped so many people, I hope you can help me.
I have a 68 Continental and the power steering fails to assist after the power steering system begins to warm up… maybe after 1 hour of the engine running. It works fine when cold, with no sounds of the pump straining.
I put the car in the air and disconnected the Pittman arm to see if the linkages were causing extra strain on the pump or steering box. Some joints moved freely with just a noticeable amount of tension to a few joints as compared to the rest. Ball joints were free as well. With the front wheels on turntables and the linkages connected without the Pittman arm connected, I can manually move the wheels left and right with slight effort but I’m not straining. Without the Pittman arm connected, I can steer at the steering wheel all day and have no issues with the steering box or pump. I reassembled the Pittman Arm, and put the car back on normal ground surface. I had a friend who is an expert in steering and suspension suggest that I install a pressure gauge between the pump and the steering box, and the readings were unusually high as I steered left and right (pressures that he was not used to seeing in a steering system). PSI reading from 600-800 PSI for normal left and right turns…without hitting the stops. Someone also suggested I get a temperature reading on the components to see which got hotter first or was the hottest…maybe indicating a restriction in the system. By the way, the wiper motor works perfectly. I’ve done a lot of research and investigating and my guess is to condemn the steering box. I’m thinking that the valving has become worn/ restricted and is sensitive to the slightest strain put on it. Any input on your part would be very helpful.
Sincerely,
Shane
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Hello Shane –
I’m not sure if you have the Factory Service Manual or not but shown in this manual are specific pressure tests for this era of Lincolns. Since you indicate that your steering is fine when cold I am leaning toward a possible pressure drop from the pump that is due to the thinner oil at normal operating temperature. If this is so, the pump may be failing. The correct p/s fluid as specified MUST be used in this system. Incorrect fluid can produce low pressure when hot. Accurate diagnosis is of course very important because of the parts and labor costs of the unnecessary replacing or repairing components that are already in good order. We are including in our reply to you a copy of the shop manual pages for pressure testing Lincoln and other p/s pressures. You can then note the high normal operating pressures needed for the Lincoln p/s system and you can also perform your tests with the fluid cold and hot in order to compare. These crankshaft mounted pumps are well known to require overhauling after all of these years and we do offer this service. If we can be of further service, do not hesitate to contact us.
Sincerely,
Bill