Power Steering goes out while driving on the road and then comes back again

[gaC5]

I have a 78. When I've been driving on the road for about 40 miles and then get off the highway my power steering goes out. Then if the car sits awhile it comes back on again. It never does it just driving in town.

 

[Mac]

Is the fluid reservoir appropriately filled? When was the last time you changed/flushed the fluid?

Does the system use the cooler in the radiator or has an aftermarket cooler been added? In either case, are you certain that it's circulating freely?

Are your belts and hoses in good condition? No slippage of the belts or bulging of the hoses?

Mac

 

[gaC5]

I never have changed or flushed the fluid. How do you do that? Thanks

Is the fluid reservoir appropriately filled? When was the last time you changed/flushed the fluid?

Does the system use the cooler in the radiator or has an aftermarket cooler been added? In either case, are you certain that it's circulating freely?

Are your belts and hoses in good condition? No slippage of the belts or bulging of the hoses?

Mac

 

[Mac]

I never have changed or flushed the fluid. How do you do that? Thanks

Power steering fluid is a form of hydraulic fluid. While it's not hydroscopic (meaning it doesn't attract/absorb water), it does contain significant additives that deplete. The usual way of changing it for home mechanics is to remove the lowest fitting and popping the cap so it will drain by gravity. That doesn't remove all of the fluid but it usually gets most of it. The small portion trapped in the system isn't that significant. The reason I asked about the cooler is what you've described might be caused by the fluid getting heated and losing viscosity.

The advice to follow might inspire the ire of some folks here who prefer to do everything themselves but life is like that.

Take it to a trusted mechanic or GM dealership. It's not an expensive job and you won't have to deal with the fluid afterwards. Don't agree to replace any parts unless they proved failure.

Mac

 

[gaC5]

Power steering fluid is a form of hydraulic fluid. While it's not hydroscopic (meaning it doesn't attract/absorb water), it does contain significant additives that deplete. The usual way of changing it for home mechanics is to remove the lowest fitting and popping the cap so it will drain by gravity. That doesn't remove all of the fluid but it usually gets most of it. The small portion trapped in the system isn't that significant. The reason I asked about the cooler is what you've described might be caused by the fluid getting heated and losing viscosity.

The advice to follow might inspire the ire of some folks here who prefer to do everything themselves but life is like that.

Take it to a trusted mechanic or GM dealership. It's not an expensive job and you won't have to deal with the fluid afterwards. Don't agree to replace any parts unless they proved failure.

Mac

I'll try that. Thanks