A lesson learned-Power steering fluid vs. ATF

[Bob Dillon]

Recently, I had the rack and pinion and power steering pump replaced in my '97 SE.

I've been a car guy for 50 years now, and I've always just used ATF in power steering pumps. The repair shop used it also. About 3 days after the repair, I had whining, even though I had made sure to bleed the steering.

I checked the PS fluid level, and the reservoir was empty. I didn't have the shop replace the hoses during the overhaul because I'd recently replaced the high side hose, and I've never had a low-side hose fail. There's a first time for everything, as we all know, so I figured the low-side hose was the culprit, as it was the only old part in the assembly. I went to the auto parts store and ordered one. As I was checking out, I noticed they had actual P/S fluid on sale cheaper than ATF, so I bought a quart.

This was on a Wednesday. I drove home and filled up the reservoir with the P/S fluid, figuring to swap out the hose on Saturday. Come Saturday morning, after putting about 300 miles on the clock, I checked the reservoir again before diving in, and, WTH? It was full, and no oil on the driveway? The pump was also noticeably quieter.

I'm as willing as any of us to get greasy, but I decided to think it over before going in, and to put off the job for a few days to see what happened. I also checked the web on the properties of Dexron versus P/S fluid, and discovered that Dexron has a viscosity of 43, while the P/S fluid was 63, both a 40 degrees centigrade (104 F).

Bottom line is that, more than a month later, the reservoir is still full, no leaks, and after I bled the P/S again, no whining. (be sure to loosen the P/S pump cap before bleeding-it's airtight, or close to it. The air in the system has to have an exit) I have no explanation for this, except possibly the seal in the P/S pump is designed for the higher viscosity fluid. Make sense?

We live and we learn, I guess. So, if your pump is whining and you're using ATF for fluid, this may be the fix.

[MattStrike]

My truck, with the 1975 power steering pump, takes ATF and doesn't seem to leak, still going strong. Might just be a thing with new(er) pumps?

[SSEiMan01]

I doubt it. My GXP uses Dex 6 from the factory as PS fluid. Maybe something about the 92-99 pumps? I notice mine whines a lot at lower RPM even though it's full. I don't mind though.

[Bob Dillon]

My truck, with the 1975 power steering pump, takes ATF and doesn't seem to leak, still going strong. Might just be a thing with new(er) pumps?

My thought as well. The car in my avatar happily uses ATF in the steering. (also a lot of premium gas.)

[ron350]

Makes me wonder if the leak was at the plastic fitting at the tank or at the metal line going to the rack?
When I replaced my PS pump it leaked at the plastic fitting until I replaced the spring clamp with a screw clamp.
This was with the original return hose and original spring clamp placed back in the exact position on the hose.

[Woosch]

Bob,

Another possibility is that the shop didn't properly purge all of the air from the system when they replaced your rack and power steering pump. As the air bled from the system while you were driving, and as the fluid displaced the air, the level in your reservoir would drop. Did you notice any signs of a leak?

[Bob Dillon]

Bob,

Another possibility is that the shop didn't properly purge all of the air from the system when they replaced your rack and power steering pump. As the air bled from the system while you were driving, and as the fluid displaced the air, the level in your reservoir would drop. Did you notice any signs of a leak?

I bled the system at the shop-it's a buddy's-before the car left the shop, including loosening the cap so the air would be able to escape. There was also a geared clamp on the return hose at the pump. It seemed to me the only leak possible was at the pump bearing. ATF was present on my driveway.

So, my advice is if you have a leak or loud whining, use P/S fluid to replace the fluid, not ATF.

Couldn't hurt, may help. Worked for me.

[Woosch]

That's good to know!