325e rack and pinion

[Brendan Daly]

I have a rack and pinion steering for a E30 that I got from the scrap yard. Is there any way to test it for leaks before I put in in the car ?

[Wayne 962]

Hmm, good question. You might be able to take it to a machine shop and have them leak test or pressure test it with some compressed air or fluid. I know they can usually do this with used oil coolers (at least my shop can)...

-Wayne

[kuehl]

Originally posted by Brendan Daly
I have a rack and pinion steering for a E30 that I got from the scrap yard. Is there any way to test it for leaks before I put in in the car ?

There are a few visuals you can do that will give a clue as to whether the rack leaked before or whether it could become a leaker:
1) Inspect rack shaft (connects to the tie rods) for signs of power steering fluid. If you see oil (typically red ATF or clear ps fluid) then you "may" have a leaker. We say may because the fluid could have gotten on the rack shaft from handling.
2) Inspect the "boot breather tube" usually a black plastic tube that attaches to the rack housing with plastic 90 deg fittings that press in. If there is fluid in this tube then you have a leaker.

The other inspections you can do yourself would be a simple "roll test". Carefully grasp the input shaft (pinion spline) with a pair of vise grips (don't clamp too much because you don't want to damage the splines). Slowly turn the input shaft left to right and "feel" the movement to see how smooth it rolls. If you feel a "lump" in one area that does not repeat itself every 360 deg of turn of the pinion then you might have a worn tooth profile. This usually occurs with high mileage racks on the "center" tooth valley. The center tooth valley is where the pinion gear's tooth would contact the rack gear most often. This would be the "dead running center position"; where the rack is gear is set when the car was aligned for dead straight ahead alignment. The center tooth valley tends to wear more than other sections of the rack gear because you are using this valley more often when you drive the car, such as driving down rather straight roads.
Pinion gears are usually harder than rack gears (measured in terms of Rockwell "C" scale") because their surface makes contact more often. So, if you find a "lump" (which is actually a feeling of sudden lack of resistance) when you turn the pinion gear a few degrees on one section of the rack shaft, and this section appears to place the rack shaft ends at equal distances existing the rack (i.e. you see 2.00" of rack shaft sticking out each end of the rack cylinder), then you probably have a worn center tooth valley.

If the you feel "lumps" more often when turning the pinion as the rack shaft's gear end exists the cylinder, this could simply be grease and dirt that has wax'd up in the gear profiles.

If you feel the rack's movement bind up at near one end when the turning the pinion left to right or right to left, this could be a sign of a bent rack.

If you feel "lumps" every 360 deg of turn on the pinion, then this could be a bent pinion gear.

There are two metal hydraulic lines attached to the rack (not the pressure from pump or return to tank) that should be inspected for bends, kinks, leaks.

You can inspect the rack shaft on the Passg. side for signs of rust, scratches, pitting.


Depending upon the year of the rack, for example prior to the 11/86 (I recall) the E30 racks were comprised of a steel cylinder with an aluminum pinion housing and 11/86 onward the cylinder and pinion bodies were a one piece casting.

As far as pressure testing, you would need to pressurize the unit to approximately 100 bars or 1450 psi, lock to lock, (and this must be done carefully as you need a hydraulic circuit that will allow for pressure relief in and exhaust in the circuit. in otherwords you need dedicated equipment or a car to test it on).

Besides testing for leaks with pressure, there are other functions of the rack to be tested, functional tests that relate to "internal" leakage in the circuit (i.e. does the rack give full power assist in both directions and with the proper curve).

[Wayne 962]

Cool (or shouold I say kuehl) - everything you ever needed to know about steering racks!

-Wayne