Hi Folks,

First post here. Reading this forum was very helpful with my first car project over the winter of completely rebuilding the front and rear suspension on my 78 that I picked up in November. Got a little problem and I'm hoping some corvette gurus can help me out.

As part of this project, I rebuilt all the power steering components (pump, valve, ram, new hoses). After bleeding the system and balancing the valve, the power steering worked great for about two minutes, then.... no more power assist. There was no noise that happened or anything, it just stopped working. I was hoping that the system hadn't been thoroughly bled, but I've made sure of that, and I'm certain something is wrong. What's strange is that if I remove the ram from the frame and try to balance it again, it does still go in and out, but slowly and weakly. For instance, if I tighten the adjustment nut on the valve all the way down, the ram comes all the way out, but I can still push it back in with my hand. It's like the pressure is very low. I also noticed that when I first started it and it was working correctly, the metal fittings on the hoses connecting to the valve were hot to the touch, but now they are just slightly warm.

So, any idea which component is bad? I'm leaning towards the pump, but I think I was most likely to screw up the rebuild of the valve (although the valve appears to be working?). Are there any tests I can do to determine which piece is bad? I'm hoping to avoid a shotgun approach to replacements.

Thanks a bunch for your time.
Mathias

 

Mathias,

I had the same thing happen and found two things. First, I didn't bleed the system correctly. I didn't bleed it with the engine off enough. Get the front wheels off the ground and turn the steering wheel lock to lock about 20 times with the engine off. Top off the fluid and start it up, turn it lock to lock a couple more times and check the fluid. You'll know when you start it up if it's working or not. If it is, then put it back on the ground and turn it lock to lock a couple times. If it's not, chances are the flow control valve in the pump is stuck. Drain the fluid and pull the high pressure hose off the pump, followed by the fitting. The flow control valve should be moving freely in the bore. It's probably stuck, using a magnet usually gets it out. Check it for burrs or anything else that might make it stick. I found that just not bleeding correctly can make it stick. Put it back together and go through the bleeding process....

 

Has nothing to do with bleeding, there is low pressure, a restriction, or a bad ram.

 

Cool - I like the idea of the flow control valve being stuck. That would also explain why the hoses aren't getting hot any more I think. I also like it because your suggestion doesn't involve spending any more $$$ on it yet.

I'll drain the pump today, inspect the flow control valve, refill and re-bleed, and report back with results.

Thanks again!

 

Excellent - you were right damoroso! The flow control valve is wedged down tight all the way down into the bore. I can't get it loose with a magnet, so I'm pulling the whole pump now. Any idea what would cause this to happen - incorrect bleeding procedure? I didn't notice any burrs or problems when I rebuilt the pump, but I wasn't looking specifically for this problem at the time.

 

Glad you found it! Yep, I've found inproper bleeding can cause this.

 

On old power steering systems, sometimes the flow control valve will have a lot of varnish on the diameter because the fluid has become oxidized through the years. Then it may stick.

Otherwise the problem could be supplier quality; possible poor machining of the pump bore, or mishandling of the flow control valve during assembly.

Jim

 

Well, after I got the pump out and apart, a good whack on the bench popped out the flow control valve. I didn't see any evidence of burs or any debris. I put the spring and valve back in the bore and pushed it through its full stroke with a brass drift several times, and it was very smooth, and I could not intentionally get it to stick. So, I put it all back together, and went through the proper bleeding procedure (from Jim Shea's docs), fired it up, and it's working GREAT! Took it out for a short drive around the neighborhood and it's still working great. Hopefully I won't be pulling the power steering pump out again for a long time. Thanks a lot for your help guys.

 

I just had the same problem on a 76 and thanks to this thread I was able to sort out the stuck valve in the pump as the problem as described by Damoroso. After I removed the pump to work on getting the valve out, I found that a 7/16 deep wall socket would turn the valve spool and finally loosened it up enough to pull it and make certain there weren't any burrs or dirt causing it to stick. If I had looked harder at the stuck spool while it was still on the car, it would have saved pulling the pump, but maybe this will help someone in the future

ANOTHER GREAT EXAMPLE OF THE VALUE OF THIS FORUM!!

Many thanks to Mathias999us and Damoroso.


Unk

 

RU7376Vettes,
I don't understand about the 7/16 deep wall socket extracting the flow control valve from the pump bore. The face of the valve pointing at you (and the discharge fitting) is round and completely smooth. Did you just use the socket to press on the valve?

Jim

 

Jim:
When I took my pump off the car and looked into the bore where the high pressure line connects after the line, nut and spring were removed, the end of the spool had a hex on the end of it. When I got the spool out the end that was towards the front of the car was round and smooth. The spring was on the other end that had the hex on it. Now you have me wondering if Bubba had been into the PS pump before me and had the spool in backwards! With all the other screwed up things I have found on this car, it would not surprise me if one of the PO's had been into the pump. I could not find a pump assembly drawing in either the Assembly Guide or the Shop Manual. After putting it all back together, my steering was better. Now you have me thinking that the spool is in backwards and the hex is an adjustment for spool position that bottoms out on the other end of the pump body. What do you think?

Unk

 

The flow control valve is in backwards!

First insert the spring, then the flow control valve. Orient the valve with the small hex screw and screen in contact with the spring. Then install the discharge fitting.

The hex on the valve controls the pump relief pressure. There is a spring inside the valve and a check ball. The position of the hex screw dictates the spring pressure inside the valve against the ball.
Jim

 

Another issue to add to the very long Bubba list on this car! Many thanks for all your kind help Jim, you are a real asset to this forum!!! Back on the lift again, this shouldn't take long to resolve now that I know how to fix it.
Thanks again,
Unk

 

What timing for this thread. I just installed a Borgeson system on my car. When I went to test the steereing, no power!! Removered the valve and cleanered it up with some scotchbright pad and reassembled. The power steering works great now!! This Forum Rocks...

 

I know this thread is old but I have the exact same problem but mine keeps sticking. Everything was fine until I decided to replace my working pump with a Cardone reman unit from Carquest. I unstuck the valve several times and it will work for a while and then stick again. I replaced the valve and pressure fitting. I replaced the entire pump under warranty (twice). Both times when I took the pump out the magnet looked like a Chia pet. On the last pump I installed a filter and did the 3F procedure Cardone recommends and I ran about 3 quarts of fluid through the system. I have another unit now that I haven't put in yet and am reluctant too until I figure out why this keeps happening. I've learned way more about C3 power steering than I ever wanted to know. If anyone can help I sure would appreciate it.

 

Although my comments don't specifically address your issue, something to consider if you still have the OEM pump is to rebuild it yourself. I had the front pulley shaft seal leaking and purchased the rebuild kit from corvette central for $20 and rebuilt it myself after being unable to find a NEW pump. Corvette central sells a new pump but it was back ordered when I needed mine about 1.5 years ago. It was easy to rebuild and works perfectly again.

A-1 Cardone is out for me as a supplier since I never buy rebuilt anything unless I have to AND I recently purchased a NEW water pump for my Chrysler 300 and a friend who rebuilds wrecked Volvos told me that the A-1 Cardone water pump that i purchased new is Chinese. Sure enough, contacted Cardone and asked and was told designed in Philadelphia and made in China. can't return it now since I bought it months ago and have to buy another water pump NEW from Gates-made in America!

 

Hi Guys, two years ago I replaced all parts of the power steering. Worked great until this summer...at some points when the engine rpm's (like pulling into and out of the driveway)are low the power steering doesn't hardly work. I rev the engine and it works. Driving around it seems fine, just balks when low rpm's. Any thoughts? Thanks,Rog

 

Either the pump is not generating adequate pressure/flow or you need a smaller pulley on it. If the pump/pulley is original to the car, then the pump has problems.

 

I wish I had the OEM pump, it was gone when I bought the car in 1990. I wish I still had the pump I started with which was the one that came off the 1989 Firebird that I got my accessory drive serp system from. Thanks for your reply, I think my plan is now to get my money back from Carquest for the Cardone reman and get Lee Manufacturing to build me a pump and set it up to the 75-79 specs. One thing I learned through all this is the 75-79 C3 original pumps were set up for more flow than most. Once I get a pump that works correctly and is set to 75 specs I will never trade it in as a core again.

 

Is it still working good? I thought I had mine fixed a few times only for the valve to get stuck again. What type of power steering fluid are you using? I learned from the full size Chevy forum something that I would like to share on this thread. A member on that forum who works on a fleet of Chevy trucks for a living was having the exact same problem as we are (was for you I hope). On every truck that they opened up the steering system on to replace anything they would start having problems with the flow control valve sticking. These trucks use a P type Saginaw pump also. After the flow control valve stuck it would ruin the pump and would have to be replaced. They were getting their pumps as brand new GM. He resolved the problem by changing fluids. They were using Johnsen's PS fluid and they switched to ATF with Lucas Trans Fix added to it. He claims that the PS fluid did have enough lubrication. Now using ATF doesn't make sense to me but he says they haven't had a problem with a single truck since they switched over a year ago. The fluid I have been using is on the Cardone list of approved fluids but now I'm thinking of switching fluids to either GM or Lee Manufacturing's fluid.