Gm Power steering pump - tech artikel

[falloutboy]

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There was a time when power steering was considered to be a convenience accessory; today it seems to be standard on most cars, including many street rods.

While power steering on street rods continues to be popular, there are also common complaints about it, usually concerning steering sensitivity. Touchy steering can be an issue with standard steering boxes and it’s quite common when rack-and-pinion steering is used. In most cases it’s the result of mixing and matching parts, but then that’s what we do, so the challenge is to find a way to make the pump and the gear work together.

In street rodding the most commonly used power steering pump is the Saginaw. To get the lowdown on how to tailor a pump to our specific needs we turned to Jeff Grantmeyer at Borgeson for his expertise. “The Saginaw self-contained power steering pump was used widely by all off the Big Three from the ’60s on up into early 2000. That being said, this has resulted in many different variations of this pump throughout the years. We won’t be dealing with the larger Saginaw ‘P-Series’ pump found on early full-size cars and Chevy/GMC medium-duty trucks but rather we’ll examine the standard Saginaw canned ham pump.”

Pump Shafts: The Saginaw self-contained pump was offered with two different pulley shafts. The 5/8-inch nut retained keyway-style shaft was used from its inception until 1974 and the 3/4-inch diameter “press-on” style shaft was used from 1975 and on.

Pressure Hose Connection: The Saginaw self-contained pump was offered with two different high-pressure hose fittings. The 5/8-inch flare connection was used from the beginning until 1979 and a 16mm O-ring connection was used from 1980 on.

Pump Mounting Studs/Holes: The mounting studs/holes changed on the same timeline as the pressure fitting above from SAE to metric.

Pump Reservoir: The Saginaw self-contained pump was offered with way too many to list return hose fitting configurations. The hose return fitting varied completely by original vehicle application. Some reservoirs had returns running up, back, left, right, forward—well, you get the idea. The Saginaw pump reservoirs were even offered with two return fittings for vehicles with a Hydro-Boost brake system.

Pump Flow/Valve Rating: This is another aspect of the pump that varied completely by original application. The OEMs would specify what flow rating was required based on vehicle weight, steering gear piston diameter, and whether or not the pump was running a Hydro-Boost brake system. The Saginaw pump in OEM applications can be set from 2.0 on up to 4.5 GPM.

Pump Bypass Pressure: Just like the flow rating above, the OEMs would specify output pressure based on the original vehicle application and what system the pump was running. Most steering gear applications would run between 1,100-1,300 psi with heavy vehicle high demand applications on up to 1,550-1,600 psi. Rack-and-pinion steering on the other hand is generally happier at a lower operating pressure of 850-950 psi.

Excessive Response/Touchy Steering: This is generally caused by excessive pump pressure. Borgeson offers a pressure reduction kit (PN 899001) that will allow the customer to adjust the internal bypass pressure of the power steering pump (self-contained and Type II with a remote reservoir). This is a very common issue on street rods running a GM pump with a Mustang rack-and-pinion.

Pressure Chart

Power Steering Pump Troubleshooting Tips from Borgeson

Inoperable Pump: There is usually one cause for a new power steering pump to be inoperable: damage during pulley installation. The pulley, although called press-on, is not to be pressed on; a pulley installation tool must be used. Failure to use the proper installation tool can crack the pump housing and cause the pump to be inoperable.

Pump Noise or Groan: This is most commonly caused by a restriction or air trapped in the system. It can also be caused by heat buildup. (This would include a loss of assist.)

No Power Assist After Recent System Service: This is most commonly caused by fluid contamination causing the pressure bypass valve to stick open, resulting in no pump pressure. To fix this, remove the flow valve and ensure the pressure bypass valve moves freely in and out. This can also be a large amount of air trapped in the system.

Hard Steering in Both Directions: This can result from insufficient pump flow/pressure, low power steering fluid level, air trapped in the system, and excessive heat buildup.

Foamy Power Steering Fluid: This is most often caused by either air trapped in the system or a leak in the return line sucking in air.

Reservoir Cap Blows Off: This is most often caused by an air leak. Air is sucked in to the power steering system compressed with the fluid and then expands when it reaches the reservoir, causing an unintended pressure buildup in the reservoir.

[falloutboy]

Ok, eigentlich wollt ich das an ein Thema anhängen wo jemand ein Problem mit seiner Servopumpe hatte. Da ich aber den Thread nicht mehr finde, und über das hier gestolpert bin.

Hier noch einmal etwas zum Thema:

Power Steering Rehab

By Jeff Smith, Photography by Jeff Smith

Car Craft, December, 2012

If you are a celebrity in America these days, it’s nearly a requirement to spend at least a week in some trendy, beach rehab facility. Thankfully, we’re not celebrities, but one of our junkyard power-steering pumps recently suffered from leak issues and cried out for rehab, so maybe we’re more tragically hip than we thought. With our minds now cleared from a synthetic power-steering-fluid-induced haze, we thought it might be interesting to show you how easy it is to put your classic GM Saginaw pump through rehab and have it come out a clean, happy, and fully functioning member of our high-performance society.

The Saginaw power-steering pump first made its appearance on GM cars in 1960. The early pumps used a threaded 5?8-inch-pulley-shaft-diameter fitted with a woodruff key. Later, GM changed to a larger, 3?4-inch shaft minus the threads and woodruff key, converting to a press-on pulley. According to RockAuto information, GM was still using this pump in some LS truck applications as late as 2009. The fittings and fasteners in later pumps merged to metric at some point but retained the same basic pump configuration, with its integral fluid reservoir. The ’65 and ’66 big-block Chevy applications used a smaller pump housing that relied on an external reservoir. If you like the idea of a separate reservoir, Original Parts Group (OPG) reproduces that pump cover. One thing that makes this pump so popular is that the same basic reseal kit will service all pumps between 1960 and 2009, and you can find one from RockAuto for less than $10.

We mentioned that the Saginaw pump went metric at some point in the later ’70s, but we discovered that the thread pitch on the high-pressure output fitting that screws into the pump is so similar that the older SAE output fitting will screw right into the metric-pump body. This is important because the older pumps use inverted-flare fittings, while the newer ones use a Saginaw O-ring fitting. So if you want to update your ’60s GM pump with a newer ’90s Saginaw pump from the junkyard, the exchange is a snap. In most cases, even pump housings will interchange. If your pump housing is beat up, Tuff Stuff offers both natural and chrome housings that will fit most applications. So this means you could snatch a newer pump out of the junkyard, slip on your original pump housing (or a new one from Tuff Stuff), add new seals, and have a virtually new pump for very little coin. Plus, you can reuse your original pressure fitting to retain your original high-pressure hoses, so you don’t have to buy new hoses. There’s also a smaller, late-model power-steering pump called the Type II that we have some tricks for, but we’ll save for a later story.

Power-Steering Pump Bleeding

If you also replaced the power-steering box, there is a simple bleeding operation you can perform that will eventually save you lots of time. Power steering is just like any other hydraulic system in that it will work best with no air in the fluid. So with a dry pump and box, fill the pump reservoir with fluid, and then with the front tires off the ground, manually turn the wheels lock to lock. This will force air out of the box and lines. Do this several times, and refill the pump with fluid as needed, until no more air bubbles appear in the reservoir. Now you can start the engine and slowly run the steering lock-to-lock. The system should not create any mechanical whine. If the system whines when running, there is still air in the system and you will have to wait 12 to 24 hours for that air to exit the system. You could also try applying vacuum to the system by drilling a hole and sealing a tube in a spare pump lid plumbed to a vacuum pump in order to draw the air out of the system.

Parts List

Description PN Source Price

Gates seal kit 351160 RockAuto $8.18

Dorman reservoir cap 82581 RockAuto 2.34

Royal Purple synthetic PS fluid 013626 Summit Racing 5.46

Borgeson flow valve-shim kit 899001 Summit Racing 16.97

PS cover for remote reservoir CH28422 OPG 90.98

AFCO PS hose kit w/steel fittings 10637102 Speedway Motors 149.99

AFCO PS fluid 10636901 Speedway Motors 8.99

Power steering pulley tool, OTC 4530 Summit Racing 38.95

Tuff Stuff reservoir, left return tube 6501C Summit Racing 39.95

Sources

American Fabricating Company (AFCO); 800/632-2320; AFCORacing.com

Borgeson; 860/482-8283; Borgeson.com

Harbor Freight; 800/423-2567; HarborFreight.com

Original Parts Group (OPG); 800/243-8355; OPGI.com

RockAuto; 866/762-5288; RockAuto.com

Royal Purple; 888/382-6300; RoyalPurple.com

Tuff Stuff; 00/331-6562; TuffStuffPerformance.com

Text zu Bildern:

01: Car crafters love interchangeability, and there are very few GM parts that have remained basically the same from 1960 to 2009. The pump on the left is the newer, metric version with a press-on pulley, while the one on the right is the older, bolt-on version with a threaded shaft and a woodruff key. To disassemble the pump, the first step is to remove the pulley. Newer pumps require a specific power-steering pump puller/installer. You can buy a decent universal puller/installer from Summit Racing for a fair price.

10: After pressing off the pulley, remove both bolts on the back side of the reservoir and remove the large, high-pressure fitting from the rear of the pump. Then, mount the pump in a vise using the flat portion of the shaft housing. The housing is press-fitted over the pump, and a few whacks with a large rubber mallet will drive the reservoir off the pump body. This will expose the one large and three smaller O-ring seals (arrows) that need replacing.

03: There are two styles of high-pressure fittings: the SAE with an inverted flare (top photo) and the later metric version that requires Saginaw fittings (right photo). The good news is that these fittings are interchangeable in the pump housing, since the thread pitch between metric and SAE is close enough not to be an issue. We’ve tried this, and it works. This allows you to use a newer, metric pump but retain your original inverted-flare hoses (that’s a Saginaw fitting in the lower photo).

04: There are two styles of high-pressure fittings: the SAE with an inverted flare (top photo, left) and the later metric version that requires Saginaw fittings (top photo, right). The good news is that these fittings are interchangeable in the pump housing, since the thread pitch between metric and SAE is close enough not to be an issue. We’ve tried this, and it works. This allows you to use a newer, metric pump but retain your original inverted-flare hoses (that’s a Saginaw fitting in the lower photo).

05: Kein text

11: If you remove the pressure-relief valve from the pump, you will see that behind it is a spring. Notice that the valve uses a small nut that retains a shim (arrow). The thickness of this shim determines the pump’s output pressure. When used with rack-and-pinion steering, these Saginaw pumps create too much pressure, making the rack feel twitchy. Borgeson makes a shim kit that increases the shim thickness, reducing peak pressure for use with rack-and-pinion steering.