Power steering fluid filter?

Down the road I'm going to plumb in a cooler for the power steering (custom C4 rack). Would it be possible to plumb in a filter of some sort on the return line, too? What's the flow rate of the original C3 pump (in this case, hooked to a rack) versus what an engine oil filter deals with? It's an expensive rack, and I'd like to do a little extra to help the longevity.

Just curious. Opinions?

69427 said:

Down the road I'm going to plumb in a cooler for the power steering (custom C4 rack). Would it be possible to plumb in a filter of some sort on the return line, too? What's the flow rate of the original C3 pump (in this case, hooked to a rack) versus what an engine oil filter deals with? It's an expensive rack, and I'd like to do a little extra to help the longevity.

Just curious. Opinions?

Click to expand...

I'm not Jim Shea, but I have used the cheap inline filters form Autozone no problem. Just cut the return line, and clamp it in. I know the coolers and filters are ALWAYS in the return line.
I also know the stock Saginaw pump has a magnet inside like a tranny pan to collect metal particles.
I put a cooler in the Winnebago return , and it dropped the temp big time. Between the steering and hydroboost, it got quite warm before.

big2bird said:

I'm not Jim Shea, but I have used the cheap inline filters form Autozone no problem. Just cut the return line, and clamp it in. I know the coolers and filters are ALWAYS in the return line.
I also know the stock Saginaw pump has a magnet inside like a tranny pan to collect metal particles.
I put a cooler in the Winnebago return , and it dropped the temp big time. Between the steering and hydroboost, it got quite warm before.

Click to expand...

Bird, I agree with everything you said up until the but.

Naw, i was thinking the same thing then realized that return hose is constantly moving around. Seems to me an in-line can would get hung up in the frame.

The blue thing on the reservoir is a filter

Through the years the maximum flow rates for C2 and C3 pumps varied quite a bit.
1963 through 1969 was 1.75 gallons per minute
1970 through 1973 was 1.60 gallons per minute
1974 through 1981 was 2.9 gallons per minute
1982 was 1.9 gallons per minute

I really don't know why the pump output was increased (almost doubled) starting in 1974.

Improved fuel economy was the reason that the flow was dropped back to 1.9gpm in 1982.

In 1975 there was a change to a internal spring in the control valve. The spring went from 55 lbs at a certain installed height to 40 lbs. A weaker spring with higher pump flow would have made the valve more responsive. (It also would have lighter effort.)

Tires were changing in the early to mid 1970s (bias belted to radials). This also may have had some influence with respect to pump flows, control valve springs, and the Corvette ride and handling engineers.

Years ago I talked to a service rep at Vette Brakes and he indicated that their rebuilt valves had 40 lb springs. He indicated that valves with 55 lb springs could be obtained from them if desired. (At the time, you could even request a 55 lb spring as part of a VB rebuild kit.) I know that this information was posted on another forum. I don't know if people ever followed up on requesting the spring. If some owners did try the change I don't recall any feedback - positive or negative.

Jim

Jim, I think we may have discussed this some time ago, but I don't recall if you had any answer...
All I did was take the '72 brass valve assy as came with the car in '95, and screwed it into the '88 vette serp pump that's on the car now, spliced the lines, and so never changed it since doing first the rack, and then the HB.....

I understand the flow and pressure should be greatly reduced from what would have been for a more 'normal' factory setup.....

guys complain about over assist from rack and brakes with the updates/conversions....yet I have no such complaints.....

would that valve react the way I think it would?? and therefore make my setups feel 'better'..??

h:

Gene,
I know that you obtained your rack & pinion gear from a salvage yard. You knew exactly what line of vehicles it came from. I don't have any proof for the following statement but years of hanging around these various forums has given me some insight. I don't believe that the rack & pinion gear rebuilders are as exacting as Saginaw when it comes to providing a valve with a specific effort.

You can easily measure rack travel and the number of turns of the pinion for movement of the rack but quantifying valve effort requires a special machine with known flows, pressure gages, and calibrated torque wrenches and a chart or scope to combine the readings. So what I am saying is that there is probably a lot more variation gear to gear and some people complain about a light effort others may be competely satisfied.

Gene, I think that you just have a good performance rack & pinion with a high effort valve (or at least a valve that you are happy with.) If I remember correctly I provided a listing of various Saginaw racks that assisted you in selecting your gear.

I also did a quick study on Saginaw pumps supplied to various truck platforms. I didn't note any real difference in flow rates or pressure relief settings on pumps provided to platforms with hydroboost versus the same platform without hydroboost.

I never worked in the pump group but I think that one of their philosophies was to provide a pump with a minimum amount of flow and pressure so that the vehicle would get the best fuel economy without sacrificing steering performance. With respect to our "custom" vehicles a bit of extra flow isn't really noticed. Since the OEM 1/4 inch ID hoses were the pressure limiting factor on C2 and C3 Vettes, when you install a rack and hoses designed for 1400 psi, running a pump with higher pressure relief settings isn't a big deal either.
Jim

Jim, it very well could have been you in late 01, that led me to the Grand Am rack being same as Idar Anderson's conversion I followed from years earlier....

I know I switched and kept the '72 pump brass valve for the flare fitting years before that even 15 years ago....I dunno how that reacts with the '88 serp vette pump....I did it for the flare fitting on the OEM steering....

makes me wonder if somehow I lucked out as I have no complaints and lots of other guys are unhappy with the feel on HB brakes and rack steering....

dunno....:friends:

69427 said:

Down the road I'm going to plumb in a cooler for the power steering (custom C4 rack). Would it be possible to plumb in a filter of some sort on the return line, too? What's the flow rate of the original C3 pump (in this case, hooked to a rack) versus what an engine oil filter deals with? It's an expensive rack, and I'd like to do a little extra to help the longevity.

Just curious. Opinions?

Click to expand...

Since you want to protect the rack, consider putting an inline filter between the pump and rack.
In a pump/valve/cylinder system, the pump is what creates the greatest contaminates.
Most serious hydraulic systems use 3 filtrations.

http://www.compressedairstore.com/38-NPT-HYDRAULIC-IN-LINE-FILTER--VITON--20-MICRON_p_2849.html

If you put a filter between the pump and the rack you will be subjecting the filter to 1500 psi when you turn near full lock. You are much further ahead by placing a filter in the low pressure return line. There may be heavy duty, high pressure filters available but with a free flowing open center system, particles are going to be filtered and trapped on the lower pressure side just as easily as the high pressure side.

Saginaw never was able to justify placing a filter in their power steering systems. The magnet inside the pump reservoir did a good job of picking up magnetic wear particles during the life of the car.

Jim

JIML82 said:

If you put a filter between the pump and the rack you will be subjecting the filter to 1500 psi when you turn near full lock. You are much further ahead by placing a filter in the low pressure return line. There may be heavy duty, high pressure filters available but with a free flowing open center system, particles are going to be filtered and trapped on the lower pressure side just as easily as the high pressure side.

Saginaw never was able to justify placing a filter in their power steering systems. The magnet inside the pump reservoir did a good job of picking up magnetic wear particles during the life of the car.

Jim

Click to expand...

Jim, I going to start another thread.....curious about how you all did stuffs....

JIML82 said:

If you put a filter between the pump and the rack you will be subjecting the filter to 1500 psi when you turn near full lock.

Click to expand...

That's the whole purpose, you use the parts required to do the task, in his case/ the OP asked to protect the rack assembly. You want the contaminants trapped before the rack. BTW, the filter I linked to, is rated at 3000psi, double the relief.

You are much further ahead by placing a filter in the low pressure return line.

Click to expand...

The oil would then be filtered after the rack, not the optimal intended protection desired.

There may be heavy duty, high pressure filters available but with a free flowing open center system, particles are going to be filtered and trapped on the lower pressure side just as easily as the high pressure side.

Click to expand...

Open or closed system, for best filtration, the components that should be filtered directly.
As far as hydraulic systems go, 1500, is a relatively low pressure system.
With a high side filter, only the relief/flow valve, hose, fittings and filter are at risk.
With a return filter, the whole system is at risk of relief pressure with dirtier oil, including the end seals in the rack, if the filter were to be blocked, and the oem return hose won't handle that either.
It looks like TT used some rated hose to plumb his in the pic he posted.

Saginaw never was able to justify placing a filter in their power steering systems. The magnet inside the pump reservoir did a good job of picking up magnetic wear particles during the life of the car.

Click to expand...

I can only imagine if they had installed filters. Can you imagine the warranty problems/complaints etc, let alone the added cost for the gazillions of systems they put out. I don't know of anyone that ever even changes the fluid in a PS system unless there is a failure.

Where are fuel injection filters?
Same in a small block engine, the filter is before the components that need protection, but it has an idiot proof feature, the bypass.

In all likelyhood, 69427 is probably attentive enough to not have to worry without a filter at all, and good oil, but filtration is a good thing, better in the right place.

Using your same logic, after installing a high pressure filter to protect the rack now you should install a low pressure filter in the return line to protect the pump. The pump has a driveshaft seal, very close tolerances in the rotating section, as well as many o-ring seals.

Since we are continuously circulating over 3 gallons of power steering fluid per minute a filter in either place is going to do the job.

Jim

Serious hydraulic systems should have 3 filters, pressure filter after the contaminate creating pump and before the expensive valves, return filter, especially in systems using hydraulic motors and then a properly sized mesh inlet screen (usually incorporating a good magnet).
The No1 cause of failure in hydraulic systems is contaminated oil.

I understand that it may be unrealistic, even for a purpose built system, especially being that small, but prevention has it's place.

The other important consideration is the fluid, and the vane pumps have traditionally used an oil with a higher zinc additive for the same reasons flat tappet motors like. I assume the GM PS fluid was high in that as well as antifoam and temp and viscosity agents.
I think it was in 07, GM issued a TSB recommending Valvoline SynPower Synthetic Power Steering Fluid to help lubricate a heated system better.

Along with a good cooler, the OP can come up with a great system.