No power on power rack

[dsraven]

here is a blurb from the hotrodders site by a guy called centreline. maybe it will help.


Someone asked the other day about a problem he was having with his Mustang II rack blowing out seals. He was running a GM pump and a Mustang II IFS power steering rack unit just like everyone else and wasn't sure why he was having the problem or what was causing it.

To begin with the GM pump puts out too much pressure for the Mustang rack. GM power steering pumps operate between 1000 and 1200 psi. Mustang II power racks were only designed to operate between 700 and 800 psi. This difference in pressure requirements can and does cause a couple problems.

First is a very "touchy" feel to the steering at highway speeds. This makes any vehicle a pain to drive for long periods since you can't really relax while driving. You have to pretty much be on top of the car at all times. The second problem is blowing out seals in the Mustang rack. You don't want to see power steering fluid puddling under your car in the driveway but it can and often does happen with this combination.

When he contacted the company that made his Mustang II kit, one of the guys there told him to just "cut" the pressure spring in the back of the pump. This is NOT the right way to lower the pressure of a GM pump. If you cut the spring it's like shooting in the dark. You never know what pressure you'll wind up with because a little taken off the spring can make a lot of difference in the pressure output of the pump. If you cut too much you could wind up with such low pressure it would be like driving with a manual rack. So, how do you correctly solve this problem?

The solution to all this is of course to lower the pressure of the GM pump and there are basically two ways to correctly do this. One is to purchase an Adjustable Power Steering Valve from someone like Heidts . They go for about $125 with all the fittings you'll need and basically mount in the high pressure line and allow you to dial the pressure you want. This method works well but for some people it can be a bit pricey.

The second solution, and the one I recommend, is to pick up a GM Power Steering Pump Flow Valve kit from Borgeson. With this kit you can easily adjust the line pressure in a GM pump to make it compatible with the Mustang II rack. The kit includes simple instructions, shims, and all the parts you'll need to do the job including a tool to hold unit in a vice while installing shims. If you are interested, take a look at page 11 of the Borgeson catalog (there's no picture but that's where its listed). The kit costs less than $30 and takes about 15 minutes to install. Best of all, it reduces the pressure the at the pump and no "add on" in line valve is required so there are less fittings to leak.

So if your Mustang II power steering is making your ride feel a bit skidish on the highway or you're rack is leaking all over your driveway, you now know a couple ways to properly solve the problem.

Centerlin

[yoshi]

I'm finding the power steering a bit flighty is that the right word? I'm turning into junctions & throwing myself about in the truck. Is it just getting used to it or should I reduce the pressure a bit more?

[dsraven]

some gm pumps are also set up to deliver 1500 psi. lower the pressure to relieve the skiddish steering or, you could fab up some brackets and use a ford pump.
hope you get it figured out. also, is the front end alignment within spec? maybe you have several issues compounding the steering feel.

[dsraven]

the Borgeson part number is 899001. summit used to sell them so not sure anymore. the previous comment was from a hotrodders post in '02. surely they or someone else would still have that kit. we haven't stopped using chev pumps on ford racks. have you tried heidts or some of the other mustangII suppliers?

[dsraven]

Summit Racing Part Number:BRG-899001. also has a pic if you google it.

[yoshi]

I've got the pressure down to 850 psi, should I go lower?

[dsraven]

if the alignment is spot on then I would try going lower with the pressure. all that can happen is the steering will become more like standard steering than power steering, right? if it helps with the twitchy feeling then it would be better, in my opinion.
is that 850 psi at idle or at a higher rpm, like what you would experience while driving? what would the pressure be at when rpm is, say, 2-3000? you could also use an under drive pulley as long as the pressure is enough at idle for those parking lot turns. that may take some stress off the pump.

[dsraven]

I would probably try to get the pressure around the 700 psi mark at 2-3000 rpm and then check what it is putting out at idle. if you get enough boost to comfortably steer in a parking situation then it would be fine, right? probably not be as twitchy at speeds either.
newer vehicles have speed regulated p/s boost for that reason. there is a solenoid valve on the pump outlet that reduces pressure at highway speeds. you could look into that as well I guess. gm has them on their stuff for sure. I think it is either higher pressure for low speeds or lower pressure for high speeds, no variable pressure. one or the other.

[yoshi]

I raised the engine revs & it was at 855 psi I couldn't see the rev counter. Under drive pulley?

[dsraven]

a chevy astro van I had, 97 vintage with 4.3 auto, was equipped with that valve. if you wanted to do a quick search at a wrecker to see what they look like.

[yoshi]

Summit wants $50 for part plus shipping to uk

[dwcsr]

we had an issue with similar steering , it was very quick steering to the point of being scary. We changed from a 2.5 turn lock to lock rack to a 3 turn rack and it solved the problem. Pressure was at 800-850 psi. Someone else here had the same issue and resolved it with a 3 turn rack

1988 FORD THUNDERBIRD 5.0L 302cid V8
ATSCO 6406 ( 3 turn) Rack and Pinion Complete Unit $ 72.79 unit from rock auto

[yoshi]

With shipping that rack would cost me $205.38

[yoshi]

I added 2 of 1/32" shims to what was already there this lowered it from 1000 to 850psi so I think ill source a 1/32" shim & put that in

[dsraven]

that's what I would try first before spending cash on a rack plus an alignment after. try to get it down between 700-800 and try it on the road again. shims are cheap. make sure the spring has room to move without bottoming on the thick shim pack. it's been awhile since I was into one of those so can't remember how much room there is or how thick of a shim can be put in without interference. anybody else have a clue?

[Hampshire]

The second solution, and the one I recommend, is to pick up a GM Power Steering Pump Flow Valve kit from Borgeson. With this kit you can easily adjust the line pressure in a GM pump to make it compatible with the Mustang II rack. The kit includes simple instructions, shims, and all the parts you'll need to do the job including a tool to hold unit in a vice while installing shims. If you are interested, take a look at page 11 of the Borgeson catalog (there's no picture but that's where its listed). The kit costs less than $30 and takes about 15 minutes to install. Best of all, it reduces the pressure the at the pump and no "add on" in line valve is required so there are less fittings to leak.

...absolutely the place to start if you are going to do it right

We changed from a 2.5 turn lock to lock rack to a 3 turn rack and it solved the problem. Pressure was at 800-850 psi. Someone else here had the same issue and resolved it with a 3 turn rack

....and that would be me. For my build, I bought a GM pump from Borgeson with their kit installed so I knew it would be properly calibrated. At first I ran a 2.5 turn rack. The PS worked fine, but the steering was too quick on the highway, so I changed to a 3 turn rack- much, much better.

Only tricky part I ran into is dealing with leaks at the pump where the lines go in. Very solvable, but that's a whole other story. If it becomes a problem, DWCSR can fill you in on that part - he's been there & knows the facts.....

[Coach529]

Following along......

[Coupeguy2001]

I know you are almost there, but just another tid bit.
I installed a GM pump and GM recirculating ball type steering box in my 57.
The thing has no feel, and you have to pay attention or it changes lanes on you.
What I did was to add 3 shims, and change the box to a rebuilt one from AutoZone, and on the hydroboost, I used a smaller fitting that feeds the power steering box.
The box I used is lock to lock 2 3/4 turns, it was out of a Z28 70 Camaro, and was termed the "quick ratio box".
So far, I have played and played with it, and like I told you previously, there is a guy here in town that can adjust the feel by using a Chrysler center internal valve body/shaft inside the box to make it feel normal. It is $168 to repair.
If you get to the point that your rack doesn't come up to expectations, you can always use a box instead of a rack.

[yoshi]

I removed one of the 1/32" shims & added a 1/16", I didn't do a pressure test but it must be around 775 now. It feels better but I noticed it felt notchy so I did some investigating & found out that the 1st grub screw from the rack on the knuckle is touching the exhaust down pipe

[mr48chev]

Progress at last.