Power Steering "weak".

[L31MaxExpress]

Just to confirm...

Since OP has PS and hydroboost (presumably both OE not retrofit) he would NOT have EVO.

My assumption: EVO is incompatible with hydroboost.

EVO and Hydroboost were used together atleast on the vans. The 1-ton donor I pulled apart had EVO.

The Astro/Safari vans also had EVO with Hydroboost. I also believe some of the GMT800 Escalades had EVO and Hydroboost as well.

 

[stutaeng]

Yes, at least on my 2000 K3500 SRW it still had EVO. When I changed my PS pump due to failure (yes, lost brakes too) I had no idea what EVO even was! My replacement pump had that little valve thing. Instructions said to take the left over connector and wrap it up with electrical tape...but I just left it hanging there.

I have no idea if my EVO was working correctly. I don't recall feeling a difference. Before and after the steering requires very little effort even at low speeds.

 

[1998_K1500_Sub]

EVO and Hydroboost were used together atleast on the vans. The 1-ton donor I pulled apart had EVO.

The Astro/Safari vans also had EVO with Hydroboost. I also believe some of the GMT800 Escalades had EVO and Hydroboost as well.

Yes, at least on my 2000 K3500 SRW it still had EVO.

Interesting. I assumed the variable orifice feature (which I interpret as variable flow control, perhaps I'm wrong) would have an effect on the HB, i.e., provide power brake assist that varied with the steering input (i.e., as the EVO varies with steering input).

As such, I assumed that the HB feature would preclude the EVO feature.

Hmm... oh well, it is what it is.

I wonder if @mpyusko has both on his. OP, what say you?

 

[HotWheelsBurban]

EVO and Hydroboost were used together atleast on the vans. The 1-ton donor I pulled apart had EVO.

The Astro/Safari vans also had EVO with Hydroboost. I also believe some of the GMT800 Escalades had EVO and Hydroboost as well.

I'm pretty sure that Rawhide, my crew cab ( very early production '97, C3500) has EVO. Where the pressure line hooks up to the bottom of the PS pump, there's a cylindrical fitting like the Burb has. As long as the system has plenty of fluid, it works fine. But I think the pump does seep a little, so replacement is in the future....

 

[Schurkey]

1. Hydroboost has a hydraulic accumulator. Just like losing vacuum supply to a vacuum booster, the booster has enough vacuum to supply power for a couple of stops. The accumulator stores enough hydraulic pressure for a couple of stops. It's entirely possible for the accumulator to go defective, though.

2. My '97 K2500 7.4L has hydroboost and EVO. (At least, there's what looks like EVO parts by the PS pump.) I don't think it works, though--steering seems pretty light all the time.

3. PS test systems are readily available for purchase. I don't expect most parts stores to keep that in their loaner-tool program, however.

4. Since I don't have PS test equipment, when it's me I pull the pressure relief valve out of the back of the pump, and look for debris/clogs. If I don't see any obvious problems, I'd replace the entire pump/reservoir/pressure relief with a suitable Treasure Yard item.

5. Yeah, I suppose you could have a defect in the steering gear or in the hydroboost that's causing low pressure system-wide. I'd suspect the pressure-relief first, pump second, though.

 

[Piratehunter]

My 97 k2500 has hydroboost and had EVO. I replaced the PS pump with one without EVO, and the lines to/from it, flushed the system, and made a huge improvement in steering

 

[someotherguy]

Y'all really muddying the waters here with all this talk about EVO. OP's truck is a 1996 so he does not have EVO.

Richard

 

[L31MaxExpress]

Y'all really muddying the waters here with all this talk about EVO. OP's truck is a 1996 so he does not have EVO.

Richard

Some 96s have EVO.

 

[someotherguy]

Some 96s have EVO.

Never seen nor heard of a 1996 GMT400 having EVO. If you think it's possible then I'd suggest you ask OP if he has it, direct him how to determine this, then proceed. I don't believe that automatically assuming he does have it is helpful, as it's very unlikely that he doesn't. If his 1996 does indeed have it I'd be very interested to know, as it would be the very first I've heard of.

Richard

 

[stutaeng]

Good point Richard. I was going to mention that it probably wasn't EVO, since that's supposed to "boost" the pressure at slow speeds. That's what I understood on that system.

OP's symptoms are lack of boost altogether. I wouldn't be chasing anything EVO related. If OP doesn't in fact have EVO, this is all moot.

Gearbox or pump are things I'd be having my eye on.