Power steering needs some help???
1st Gear
Joined: Feb 2012
Posts: 1
Likes: 0
Jim, some questions for you.
GM has a real problem with inadequate fluid flow on some platforms. Heavy engines, bigger tires, aftermarket wheel offset, etc illuminates the problem, which is most noticeable at idle parking scenarios where brakes (hydroboost) robs flow further. In these scenarios, steering assist suffers unless engine rpm is increased during the maneuver.
1. Is there a reason to expect flow to increase at idle rpm with a modified flow fitting?
2. What is the function of the larger hole on the wall of the fitting, closest to the flow control valve?
3. Can the large flow control spring lose rate over time, creating recirculation (bypass) even at idle/low flow condition?
I have examined a couple of reman pumps and noticed that the fit of the flow control valve in the port is not very tight, there is obvious play.
4. Can blowby recirculation be a factor, particularly in reman pumps?
Michael
GM has a real problem with inadequate fluid flow on some platforms. Heavy engines, bigger tires, aftermarket wheel offset, etc illuminates the problem, which is most noticeable at idle parking scenarios where brakes (hydroboost) robs flow further. In these scenarios, steering assist suffers unless engine rpm is increased during the maneuver.
1. Is there a reason to expect flow to increase at idle rpm with a modified flow fitting?
2. What is the function of the larger hole on the wall of the fitting, closest to the flow control valve?
3. Can the large flow control spring lose rate over time, creating recirculation (bypass) even at idle/low flow condition?
I have examined a couple of reman pumps and noticed that the fit of the flow control valve in the port is not very tight, there is obvious play.
4. Can blowby recirculation be a factor, particularly in reman pumps?
Michael
Le Mans Master
Joined: Jul 2000
Posts: 6,001
Likes: 111
From: Saginaw Michigan
Jim, some questions for you.
GM has a real problem with inadequate fluid flow on some platforms. Heavy engines, bigger tires, aftermarket wheel offset, etc illuminates the problem, which is most noticeable at idle parking scenarios where brakes (hydroboost) robs flow further. In these scenarios, steering assist suffers unless engine rpm is increased during the maneuver.
1. Is there a reason to expect flow to increase at idle rpm with a modified flow fitting?
2. What is the function of the larger hole on the wall of the fitting, closest to the flow control valve?
3. Can the large flow control spring lose rate over time, creating recirculation (bypass) even at idle/low flow condition?
I have examined a couple of reman pumps and noticed that the fit of the flow control valve in the port is not very tight, there is obvious play.
4. Can blowby recirculation be a factor, particularly in reman pumps?
Michael
GM has a real problem with inadequate fluid flow on some platforms. Heavy engines, bigger tires, aftermarket wheel offset, etc illuminates the problem, which is most noticeable at idle parking scenarios where brakes (hydroboost) robs flow further. In these scenarios, steering assist suffers unless engine rpm is increased during the maneuver.
1. Is there a reason to expect flow to increase at idle rpm with a modified flow fitting?
2. What is the function of the larger hole on the wall of the fitting, closest to the flow control valve?
3. Can the large flow control spring lose rate over time, creating recirculation (bypass) even at idle/low flow condition?
I have examined a couple of reman pumps and noticed that the fit of the flow control valve in the port is not very tight, there is obvious play.
4. Can blowby recirculation be a factor, particularly in reman pumps?
Michael
Here are my answers to the best of my knowledge:
1. Idle flow will not increase with larger outlet fitting throat diameters. At idle, the flow is controlled by the displacement of the pump itself. A larger rise cam is needed to increase the flow at idle.
2. I think the hole on the end of the discharge fitting is to prevent the flow control valve from restricting flow when it is hard against the end of the fitting.
3a. I am not aware of flow control valve springs losing compression load. But anything is possible.
3b. The fit of the flow control valve to the pump bore is very critical. Excessive clearance would translate to increased blow-by and loss of flow under all conditions. I know that Saginaw held the pump bore inside diameter and the flow control valve outside diameter extremely close. I don't recall the exact clearance numbers. We did competitive analysis of Toyota pumps and found that they had to zone their parts (measure and match) in order to obtain the tight clearances that Saginaw held as produced.
Jim
Advanced
Joined: Jun 2007
Posts: 94
Likes: 0
From: Salem NH
My power steering works most of the time. Sometimes tho, at slower speeds I have to really rev the engine to get it to be power steering again. It just goes non power...should I check the valve, part no. 6, inside the pump?
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
I just tried this yesterday. A 1/8 inch (0.125") drill bit was a sloppy fit in the passageway, and a 9/64" (0.141) would not fit. So I guess the origional orifice was something like 0.130". Drilled it out with the 9/64, cleaned and deburred it, and replaced it. So I increased the cross sectional area of the orifice by maybe 17%. Hope it's not too much.
Test drove at about 9:30 PM last night.
Nice.
I like it.
Test drove at about 9:30 PM last night.
Nice.
I like it.
Drifting
Joined: Mar 2011
Posts: 1,886
Likes: 9
One thing about opening the throat of the discharge fitting is that more flow also translates to higher system fluid temperatures. More flow out of the pump causes higher back pressures down stream and the pump has to work a bit harder. This will cause somewhat higher system temperatures. I'm not saying that you will need a cooler but just be aware of this drawback.
Jim
Jim
Thread Starter
Safety Car
Joined: Mar 2007
Posts: 3,652
Likes: 49
From: Bridgewater nj
Hope that helps.
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Instructor
Joined: Jan 2009
Posts: 163
Likes: 1
From: Port Allen Louisiana
This might be an odd ball question but is there anyway to boost the power steering on these old vettes? Mine is an 82 and because of authritis I'm starting to have a had time with parking. I thought there might be a way to bump up the hydralic pressure but I can't find anything on line.
Instructor
Joined: Oct 2011
Posts: 153
Likes: 0
From: Des moines Iowa
I had a similar problem. Someone told me about the stuff so I tried it. I sucked all the fluid I could out with a fluid pump. I then added 16 oz. of Lucas Power Steering Conditioner and Stop Leak. I then finished filling the reservoir up with fresh power steering fluid. It made a world of difference. It was a cheap fix, and that was about 4 years ago.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,398
From: SW Florida.
and if you don't like the result?
One thing about opening the throat of the discharge fitting is that more flow also translates to higher system fluid temperatures. More flow out of the pump causes higher back pressures down stream and the pump has to work a bit harder. This will cause somewhat higher system temperatures. I'm not saying that you will need a cooler but just be aware of this drawback.
Jim
Jim
Intermediate
Joined: Dec 2013
Posts: 35
Likes: 1
I went a different route to increasing the power steering output. I tried replacing the power valve and pump, wheel alignments, and played with the pump valve modification as listed in the above post without any luck.
I replaced the springs in the power valve. The spool in the power valve must move to provide the assisted power steering. By replacing with a weaker/lighter set of springs the spool will move side to side with less effort applied. Look at how the power valve works and you will see what I'm talking about. One must use caution to not install to weak a spring to provide to much assist. I made this modification around 20-25 years ago and can't tell you what springs I used.
This made the 74 vette a different car. I actually hated driving the car at first but loved the lines. After the power valve modification I then loved driving the car. Much lighter feeling and didn't drive like a tank around town.
I replaced the springs in the power valve. The spool in the power valve must move to provide the assisted power steering. By replacing with a weaker/lighter set of springs the spool will move side to side with less effort applied. Look at how the power valve works and you will see what I'm talking about. One must use caution to not install to weak a spring to provide to much assist. I made this modification around 20-25 years ago and can't tell you what springs I used.
This made the 74 vette a different car. I actually hated driving the car at first but loved the lines. After the power valve modification I then loved driving the car. Much lighter feeling and didn't drive like a tank around town.
Burning Brakes
Joined: Oct 2015
Posts: 781
Likes: 113
I guess the first question is, are you sure your steering is working properly now? These aren't designed to have so much assist that you can turn the wheel with a finger, but they aren't that tight if things are working properly. If you have a stuck flow control valve, faulty control vavle or some other failure, that's an entirely different issue. Then there's the problem that these systems were designed to work with a specific pressure, if you go over that, I'd think you run the risk of blowing seals or hoses.
That being said, you could always swap to a Borgeson steering box or a rack system if you need more power assist.
That being said, you could always swap to a Borgeson steering box or a rack system if you need more power assist.
Same here and before making any modification..Check the power steering fluid AND see that the level is proper on the little dipstick based on TEMPERATURE..COLD will be lower level than hot..Also check the belt,,
yes it's not easy to be older..but check the simple stuff first..IF you have anyone in a local club who has a similar system..have them try your steering..and you try theirs...Jim
"
Burning Brakes
Joined: Oct 2002
Posts: 914
Likes: 14
From: Aberdeen, Scotland
I still don't fully understand that if Hydroboost is added does it change the dynamics sufficiently enough to require a PS pump upgrade? A low speeds after the accumulator is drained braking is dangerous, when parking both braking and steering is nearly impossible. I am running 245 tires up front. Mind you the issue seems to have gotten worse, thinking the pump is fading or I just NEED more flow. I see that Corvette Pacifica offers both an OEM and a Saginaw pump, with the later being new and cheaper! I know I can adjust the pressure output, but I don't think is this the way forward.
Any ideas? ... I want to take this old girl to the track someday!
Any ideas? ... I want to take this old girl to the track someday!
Drifting
Joined: Sep 2006
Posts: 1,986
Likes: 21
From: Columbus MN
I still don't fully understand that if Hydroboost is added does it change the dynamics sufficiently enough to require a PS pump upgrade? A low speeds after the accumulator is drained braking is dangerous, when parking both braking and steering is nearly impossible. I am running 245 tires up front. Mind you the issue seems to have gotten worse, thinking the pump is fading or I just NEED more flow. I see that Corvette Pacifica offers both an OEM and a Saginaw pump, with the later being new and cheaper! I know I can adjust the pressure output, but I don't think is this the way forward.
Any ideas? ... I want to take this old girl to the track someday!
Any ideas? ... I want to take this old girl to the track someday!
I increased the flow but I'm still don't have power assist to either brakes or steering. Checking the actuator rod length and projection into the master cylinder is the next thing I'm going to check.
C3. 427, 4-link, c7 z06
Joined: Sep 2019
Posts: 987
Likes: 200
From: Virginia
I rebuilt my 76 with a kit from mid American or ecklers about 10 years ago and thought it worked great and frankly was easier than my modern challenger to turn. A little too light I always thought. No leaks anymore either. Maybe yours isn’t working properly?
Last edited by Corvettedave02; Dec 17, 2019 at 06:23 PM.
Heel & Toe
Joined: Jun 2018
Posts: 22
Likes: 0
Power steering hose leak at 1400 psi?
I know that this may not sound correct but trust me! You don't want more absolute pressure from your pump, you want more flow in order to reduce the amount of effort to turn the steering wheel. When you have more flow, pressure builds quicker, your steering will be more responsive, and your effort at the steering wheel will be less. Your Corvette pump puts out a controlled flow of around 2.9 gallons per minute.
You could try this, obtain a power steering pump from a Chevrolet Astro van (or the GMC equivalent - the name escapes me right now.) The connector & fitting assembly #24 is threaded into the back of the pump. This fitting controls the amount of flow out of the pump. Astro van pumps have fittings that allow pump fluid output of something like 3.3 gallons per minute. You want to swap that fitting with the one in your pump. It should increase the flow by a measurable amount.
You do NOT want to swap the control valve assembly #6 behind the discharge fitting. That valve will increase the absolute pressure that the pump can produce. The control valve assembly inside your Corvette pump was designed to limit pump pressure to around 1000 psi. The control valve in the Astro van is set at 1400 psi. There is a good chance that your Corvette hoses will leak from the increased pressure if you swap the control valves.
However, while you have removed the fitting assembly from your pump, reach into the pump with a rod and press on the control valve assembly. It should easily slide inside the pump bore and compress the spring #5 behind it. If it feels sticky or binds, it could cause your steering effort to increase and feel like manual steering.
Good luck,
Jim
You could try this, obtain a power steering pump from a Chevrolet Astro van (or the GMC equivalent - the name escapes me right now.) The connector & fitting assembly #24 is threaded into the back of the pump. This fitting controls the amount of flow out of the pump. Astro van pumps have fittings that allow pump fluid output of something like 3.3 gallons per minute. You want to swap that fitting with the one in your pump. It should increase the flow by a measurable amount.
You do NOT want to swap the control valve assembly #6 behind the discharge fitting. That valve will increase the absolute pressure that the pump can produce. The control valve assembly inside your Corvette pump was designed to limit pump pressure to around 1000 psi. The control valve in the Astro van is set at 1400 psi. There is a good chance that your Corvette hoses will leak from the increased pressure if you swap the control valves.
However, while you have removed the fitting assembly from your pump, reach into the pump with a rod and press on the control valve assembly. It should easily slide inside the pump bore and compress the spring #5 behind it. If it feels sticky or binds, it could cause your steering effort to increase and feel like manual steering.
Good luck,
Jim
it would just shorten the life of the hose the higher you go. A well-made high pressure power steering hose has of working PSI rating of about 1,500 PSI so again 1400 PSI would not be a problem unless the hoses will bad to begin with.
if you're going to give advice at least make sure the advice you giving is accurate. I only say this because of my 53 years experience in the automotive field and in that. Of time you make a lot of mistakes what you learn from. Nobody's perfect and we'll always learning unless we have a head in a box.
BTW, I agree with increasing flow. Also check your ball joints. I had a customer that swore the slave cylinder was bad because he wasn't getting the power assist that it should have and the customer is always right. I replaced it and it was the same way. He insisted I replace it. While I had the car up in the air I checked the whole thing out, which is the right way to do it, turns out that both of the lower ball joints we're almost seized. I mean with the tie rod disconnected I really had to put both hands on the Tire to move it. Make sure someone didn't crank down on the steering box adjuster. They do that thinging it will stop the 3" - 4" steering wheel play. Nope! It just makes it harder to turn the wheel.
So go over the whole front end suspension to make sure the problem is not being caused by more thsn one thing.
Last edited by Cobratei; Aug 7, 2020 at 06:32 PM.
Burning Brakes
Joined: Sep 2002
Posts: 1,009
Likes: 62
From: Houston Tx
I know that this may not sound correct but trust me! You don't want more absolute pressure from your pump, you want more flow in order to reduce the amount of effort to turn the steering wheel. When you have more flow, pressure builds quicker, your steering will be more responsive, and your effort at the steering wheel will be less. Your Corvette pump puts out a controlled flow of around 2.9 gallons per minute.
You could try this, obtain a power steering pump from a Chevrolet Astro van (or the GMC equivalent - the name escapes me right now.) The connector & fitting assembly #24 is threaded into the back of the pump. This fitting controls the amount of flow out of the pump. Astro van pumps have fittings that allow pump fluid output of something like 3.3 gallons per minute. You want to swap that fitting with the one in your pump. It should increase the flow by a measurable amount.
You do NOT want to swap the control valve assembly #6 behind the discharge fitting. That valve will increase the absolute pressure that the pump can produce. The control valve assembly inside your Corvette pump was designed to limit pump pressure to around 1000 psi. The control valve in the Astro van is set at 1400 psi. There is a good chance that your Corvette hoses will leak from the increased pressure if you swap the control valves.
However, while you have removed the fitting assembly from your pump, reach into the pump with a rod and press on the control valve assembly. It should easily slide inside the pump bore and compress the spring #5 behind it. If it feels sticky or binds, it could cause your steering effort to increase and feel like manual steering.
Good luck,
Jim
You could try this, obtain a power steering pump from a Chevrolet Astro van (or the GMC equivalent - the name escapes me right now.) The connector & fitting assembly #24 is threaded into the back of the pump. This fitting controls the amount of flow out of the pump. Astro van pumps have fittings that allow pump fluid output of something like 3.3 gallons per minute. You want to swap that fitting with the one in your pump. It should increase the flow by a measurable amount.
You do NOT want to swap the control valve assembly #6 behind the discharge fitting. That valve will increase the absolute pressure that the pump can produce. The control valve assembly inside your Corvette pump was designed to limit pump pressure to around 1000 psi. The control valve in the Astro van is set at 1400 psi. There is a good chance that your Corvette hoses will leak from the increased pressure if you swap the control valves.
However, while you have removed the fitting assembly from your pump, reach into the pump with a rod and press on the control valve assembly. It should easily slide inside the pump bore and compress the spring #5 behind it. If it feels sticky or binds, it could cause your steering effort to increase and feel like manual steering.
Good luck,
Jim