98 GMC EVO Fustration

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Curt
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Joined: Wed Oct 09, 2013 2:38 pm

98 GMC EVO Fustration

Unread post by Curt » Wed Oct 09, 2013 2:46 pm

1998 GMC Sierra 4x4 6.5 Diesel. Turned steering wheel while stopped, felt like ABS went off. Rapid vibrations through steering column and brake pedal. Replaced pump and EVO assembly, now I have no pressure. Removed pressure line from EVO assembly and observed only slight dripping at idle. The pump is new and shaft is fine. Could the Steering Wheel Position Sensor have caused this? Will the EVO completely restrict flow if it is not receiving a signal? Hoping to narrow it down before I replace the SWPS but I think this would be the last option?

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carriedi
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Re: 98 GMC EVO Fustration

Unread post by carriedi » Wed Oct 09, 2013 10:01 pm

have you scanned to see if you have a evo code?
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TerryAuto
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Re: 98 GMC EVO Fustration

Unread post by TerryAuto » Wed Oct 09, 2013 10:05 pm

Curt wrote:1998 GMC Sierra 4x4 6.5 Diesel. Turned steering wheel while stopped, felt like ABS went off. Rapid vibrations through steering column and brake pedal. Replaced pump and EVO assembly, now I have no pressure. Removed pressure line from EVO assembly and observed only slight dripping at idle. The pump is new and shaft is fine. Could the Steering Wheel Position Sensor have caused this? Will the EVO completely restrict flow if it is not receiving a signal? Hoping to narrow it down before I replace the SWPS but I think this would be the last option?
The first problem you describe does not sound like a steering problem at all, so not sure why you replaced the power steering pump and EVO. You have an ABS problem. That is why you felt the brakes activate with a feeling like ABS, because it WAS the ABS. Yes, you can also feel it though the steering wheel.

See this link for a common problem for GM truck ABS activation when turning.

As for the no power steering and the steering wheel position sensor, see this link for a description of Vehicle steering stability.
The SWPS cannot cause a no power steering problem, especially not a no pressure in the line problem. Here is a link for what that sensor can cause. Code C0455 and C0244.

Sounds to me like you got a bad new power steering pump.

Curt
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Joined: Wed Oct 09, 2013 2:38 pm

Re: 98 GMC EVO Fustration

Unread post by Curt » Wed Oct 09, 2013 10:47 pm

Thanks for the replies. I did scan it, no codes. I changed the pump because I heard clicking at the back of it.assumed it was the evo valve opening and closing rapidly, hence the vibration. The vibration continued in park with no brake application. Was curious about the SWPS because it controls the EVO valve.thought if the SWPS was not providing the EVO with a signal it may leave the valve closed causing the new pump to bypass internally? First time I've dealt with a steering system like this. I do appreciate the input.

Curt
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Joined: Wed Oct 09, 2013 2:38 pm

Re: 98 GMC EVO Fustration

Unread post by Curt » Wed Oct 09, 2013 11:07 pm

I am going to reinstall my old pump assembly tomorrow. It was making pressure when I removed it, try to rule out the new pump being faulty. Not the first time I suppose.

Curt
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Joined: Wed Oct 09, 2013 2:38 pm

Re: 98 GMC EVO Fustration

Unread post by Curt » Thu Oct 10, 2013 3:19 am

Just laying before bed, thought I would post every bit of detail at the time the problem started. Im sure someone has had the same problem. Pulled up to the driveway and came to a full stop, switched from drive to reverse still stopped, turned steering wheel while stopped and vibrations commenced. Could feel them through the steering wheel and brake pedal. Steering was severely diminished but got her off the road and into the driveway. Placed transmission in park and left vehicle running. Clicking noise coming from vicinity of EVO component on the pump. At an idle I could feel vibrations through the steering wheel and (brake pedal with hand only, no brake application). Would this not indicate the EVO is trying to open and close rapidly (false signals)?. If it were an ABS issue would that not mean the HYDRO-BOOST would have to be activating rapidly on its own? The vibration was felt through the steering and brake pedal in park, no brake activation. The only component that links these two is the power steering pump. And since there was an audible clicking at the rear of the pump would this not point to a faulty EVO component or that the EVO is being sent erratic signals? Im not saying it isn't ABS related, but it seems like the pump is the source. If the pressure out is repeatedly opened and closed you should feel it pulsing through the brake pedal as this is a hrdroboost system which is powered by the Steering pump, especially when you consider the vibrations were there after the vehicle was in park and no foot pedal input? I humbly say again that this is the first time I have worked (trying to) on this type of system. I appreciate any and all input and hope to be able to pay it forward.
Cheers.

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carriedi
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Re: 98 GMC EVO Fustration

Unread post by carriedi » Thu Oct 10, 2013 10:46 am

I think you are on the right track about putting your old pump back on when it comes to the no power assist with the new pump.
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Curt
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Re: 98 GMC EVO Fustration

Unread post by Curt » Thu Oct 10, 2013 2:09 pm

Put the old pump back on, and its making pressure so the new one will be going back. Still having the issues. Try to turn the wheel and it feels like the pump is laboring and pulsating. Pulled the connector to the EVO and no change. Pulled the 60 amp fuse on the fenderwell for the ABS and still no change. Im not sure if pulling the fuse would deactivate the ABS if that was the source of the problem?

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carriedi
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Re: 98 GMC EVO Fustration

Unread post by carriedi » Thu Oct 10, 2013 2:29 pm

so are you taking it back and getting another new pump?
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