'91 Lumina Euro power steering failure

My son's Lumina had the power steering fail SUDDENLY tonight. No warning. The belt is fine and the fluid level is fine. No visible leaks. Any clues?

Spool valve in the rack might have frozen up, power valve in the pump may have failed....blockage in the lines...

Pump's not moaning or anything? When the engine's running is the fluid circulating in the reservoir, or just sitting there?

Also make sure the SHAFT of the pump is turning...seen a couple of GM pumps spin the pulley on the shaft (press fitted) but usually the pulley will fall off soon after...

Thanks for posting Jeff!

I do not believe I heard any noise coming from, the pump. I did not look into the reservoir while the engine was running. I take it from your comment that I should see fluid movenement in there? I will check on that. I will also confirm that the shaft is turning but I think I would have picked up on this if is not.

How can I troubleshoot whether "Spool valve in the rack might have frozen up, power valve in the pump may have failed....blockage in the lines." ?

Thanks again!

Mike V.

When nothing is happening, pressure coming off the pump impeller that isn't doing anything pushes the relief valve open, allowing it to recirculate back the reservoir, so you'll see it stirring around in there....

When you turn the wheels, fluid level should drop a bit as the high pressure flow is diverted to do some work. Fluid will still circulate, as it's pushing fluid return back through the low pressure hose now, but you'd probably notice a change in direction, on most units.

Depending on the reservoir design, you might have to suction out enough fluid so that you are seeing right into the reservoir cavity, rather than the neck...but I'm thinking you have the old square box-type reservoir with no neck, so you should be already looking straight into it, even when full.

If no circulation at all, something really catastrophic has happened, like I said the pulley could be spun on the shaft, or the pump impeller may have done something similar inside the pump. I'd probably try cracking the high pressure line open a bit and verify that there's no pressure from the pump, if it's accessible with the pump mounted up. No pressure, a new pump is called for.

If the impeller went bad, I'd definitely recommend flushing the system, the lines and rack may be full of shavings from the disintegration. They'll ruin a new pump, and probably the rack, in short order.

If you have circulation and pressure, the problem is likely the spool or a line blockage. If the spool went bad, it's new rack time, unless a blockage is the problem...and maybe even then.

I don't really know any good way to check for a blockage other than to remove the lines at both ends and see if they are clear by blowing through them or whatever. Or crack the high pressure line fitting slightly at the rack, see if you have strong pressure there....if so, I'd say the rack is shot.

Return line blockage is probably not likely, but you might check to make sure there's not a screen in the pump side of the return, I have seen it before, I don't know if these have it though. You take the return line off and you can see it in the hole and can usually remove it for cleaning. I've seen this more on imports though...

GM racks usually go bad starting with morning stiffness, but not always. If it has a blocked orifice inside you might be able to blow it clear with compressed air through the line fittings (from low side to high, I'd imagine) but I never tried, I'm just guessing.

I do remember seeing a couple of pumps on the older GMs like yours just fail suddenly, I'm hoping that's your problem...a lot easier than a rack replacement.

Thanks again Jeff. That will give me some things to investigate. Weather man says this weekend temperatures will be alot nicer than the teens we've been dealing with so I will get some driveway time in.

I think I'm looking right into the "box" part of the reservoir when I remove the cap (no long filler neck) so I guess I should easily be able to see any turbulence in there,.

I can only say that the fluid looked quite brown when I checked it last Friday night.

Mike.

I suppose if the relief valve failed stuck open the pump wouldn't produce enough pressure for assist....if the pump seems bad, you could see if that valve is accessible and serviceable...it's just a spring loaded ball check-type valve...if I remember right...

Finally have a chance to close the loop on this....

First thing I did was I checked the cost of a replacement pump and my local Autozone had a rebuilt one on the shelf for $40.00. I figured that at that price, I would go against my pricnciples and "shotgun" one in and hope that it solved the problem. Well, it did! And as it turns out, the job would have been pretty quick and easy if:

1. The power steering pump pulley puller I borrowed was not damaged and
2, I had done everything is the exact proper sequence (for example, I had to remove the pump a few times because I did not make plumbing connections before I actually installed the pump mounting screws.)

My guess at this point is that the relief valve was stuck open. I say this because the fluid was VERY dirty and I could see how it could stick a valve. When I installed the new pump, I ran the return line from the rack to a drain pan and ran a few reservoir worths of fluid through the system until the return fluid looked clear and clean.

Thanks again for the comments Jeff. I don't know how I would have gotten at the relief valve to clean it out. The replacement pump is a little different in that respect. There is a plug there that I believe I could have pulled to access it. The old pump was strictly a casting with no apparant access.

I'll be talking with next time this old Lumina acts up. Just hoping it lasts until Fall...

Mike V.

Finally have a chance to close the loop on this....
. When I installed the new pump, I ran the return line from the rack to a drain pan and ran a few reservoir worths of fluid through the system until the return fluid looked clear and clean.

.

Good job, most neglect this step and ruin the new pump pretty quick too.

Glad it worked out!

Hey, I forgot to ask...

When I was getting ready to flush the system, I had planned to crank the engine on the starter motor - but not start the engine. I could not come up with an easy way to disable the ignition system that I was confident would not damage any of the ignition system components. Finally I just cranked it and shut it off as soon as it started. It actually worked out fine this way but I would still like to know how to safely disable the ignition. Anyone know?

Thanks again,

Mike V.

I would think pulling the harness from the ICM (module under the coilpacks) would be safe.

When I flushed them I had a helper start the car and turn the wheel back and forth to the locks while I poured fluid in as fast as it pumped out. I'd have them shut it off when I was about to run out.

I used Dexron ATF for flushing, it's cheaper than PS fluid and has high detergency for cleaning. And it mixes with PS fine, long as you don't have an oddball car that requires mineral oil PS fluid, like some imports.