NEW P/S pump, nothing at idle or below 15mph

[TwistedTahoe]

I’ve got a 99 Tahoe 5.7L. I have put on 2x New Carquest pumps (P/N #988748CQ) I did one new pump, had the issue described in the title. I chalked it up to being a bad part and just slapped on a pump from a junkyard. All was fine until that blew up doing donuts (stupid i know). I figured I’d try the new Carquest pump and to my surprise, it has the same issue (as described in the title). I had transferred the sensor that hangs off the back onto all 3 pumps from the original so it can’t be that either. Any help with diagnosing this would be appreciated. I’m about to gut the spring and plunger from where the fitting screws into the pump itself.

 

[SAATR]

Their pumps may just be garbage, especially since the only used pump that you've installed worked fine. The alternative is that the new pumps are air bound, and you'll have to try some alternate bleeding procedures to get the pump to prime.

If you remove the pressure regulating valve from inside the pump, your pump won't function as all the flow generated by the pump will be dumped back to the reservoir. The valve is absolutely necessary for the pump to function. I have a tutorial on disassembling and resealing the pump in the Suspension forum.

 

[TwistedTahoe]

Their pumps may just be garbage, especially since the only used pump that you've installed worked fine. The alternative is that the new pumps are air bound, and you'll have to try some alternate bleeding procedures to get the pump to prime.

If you remove the pressure regulating valve from inside the pump, your pump won't function as all the flow generated by the pump will be dumped back to the reservoir. The valve is absolutely necessary for the pump to function. I have a tutorial on disassembling and resealing the pump in the Suspension forum.

if it was air bound, wouldn’t I have nothing at all? I don’t know much, so take that with a grain of salt. What would be some alternate ways to bleed it? What I did was I just topped it off and went locked to lock idling and it was fine for like 5 miles and then I had nothing at low speeds/idle

 

[SAATR]

if it was air bound, wouldn’t I have nothing at all? I don’t know much, so take that with a grain of salt. What would be some alternate ways to bleed it? What I did was I just topped it off and went locked to lock idling and it was fine for like 5 miles and then I had nothing at low speeds/idle

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This is from Lee Power Steering, but is similar to a lot of procedures I've seen. Essentially, bleed with system by raising the wheels and turning the steering wheel back and forth until all air is purged from the system. Prevents damage to the pump internals due to air. Other than that, I would speculate that the pumps you're buying are just junk, and you should get another used one and inspect/reseal it yourself and call it done.

 

[AuroraGirl]

your flow control valve may be sticking or similar. pull the valve out of the rear of the pump,m NOT to play with the internals but to check the bore and the valve for damage. Do you have the original pumps valve? Try swapping.

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basically you want to see the bore that flow control valve rides in

 

[Orpedcrow]

Here’s some steering stuff from the FSM

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[Schurkey]

I just topped it off and went locked to lock idling and it was fine for like 5 miles and then I had nothing at low speeds/idle

Did you ever re-check the fluid level?

Sounds to me like the fluid level is low, gets aerated, and the assist goes away because foam doesn't transfer pressure very well.

 

[TwistedTahoe]

This is from Lee Power Steering, but is similar to a lot of procedures I've seen. Essentially, bleed with system by raising the wheels and turning the steering wheel back and forth until all air is purged from the system. Prevents damage to the pump internals due to air. Other than that, I would speculate that the pumps you're buying are just junk, and you should get another used one and inspect/reseal it yourself and call it done.

Any reccomendation for a good pump? I'm just going to return this one and get maybe an ACD or GM Genuine from rockauto if not. I figured it'd be a good pump because it was $250 out the door

 

[SAATR]

Any reccomendation for a good pump? I'm just going to return this one and get maybe an ACD or GM Genuine from rockauto if not. I figured it'd be a good pump because it was $250 out the door

The Genuine GM on RockAuto should be perfectly fine.