Dead 'Rack: Diagnosis Confirmation

Cm452 · 01-31-2019, 06:43 PM

My 08 xi has spontaneously developed vey weird steering in the cold, almost like the pump can't catch up to sudden inputs. I did a full flush with chf11s and little improved.
No leaks and no noises, but the wheel will be super heavy, then very light, then heavy again.
Gets worse as temps drop. It also will not return to center, which also gets worse as temps drop. Additionally, when turning into a corner the wheel turns to granite, and then halfway through it gets wicked light - same wheel position.

I've got a brand new suspension all around, yup, everything except tie rod ends.
Casual search suggests a) the sky is falling and b) it's likely a blown rack.
It does it faintly when the wheels are off the ground, too.
I've never seen a rack fail this way in 10yrs of wrenching on cars, fwiw.
Maybe a bad steering u joint?
TIA.
-Cm

nsjames · 01-31-2019, 08:55 PM

I'd suspect pump before I suspected rack. Pressure relief spring failed?

you'd have to get a pressure gauge on things to find out properly.

nsjames · 01-31-2019, 08:58 PM

also, maybe it's starving for fluid because the filter in the reservoir is plugged?

Cm452 · 02-01-2019, 03:53 PM

I'd imagine that if it were starved of fluid it would moan, like most hydraulic pumps when the fluid gets low. As for the pressure test; is there a port that I can tap into, or do I have to jury rig something onto the banjo fittings?
Did these cars come with variable ratio/ variable assist? I've got the sport package if that tells you anything...
-Cm

01-31-2019, 06:43 PM	#1
Cm452 Private 8 Rep 80 Posts Drives: 08 335XI, stock...for now Join Date: Oct 2018 Location: Boston Metro iTrader: (0)	Dead 'Rack: Diagnosis Confirmation My 08 xi has spontaneously developed vey weird steering in the cold, almost like the pump can't catch up to sudden inputs. I did a full flush with chf11s and little improved. No leaks and no noises, but the wheel will be super heavy, then very light, then heavy again. Gets worse as temps drop. It also will not return to center, which also gets worse as temps drop. Additionally, when turning into a corner the wheel turns to granite, and then halfway through it gets wicked light - same wheel position. I've got a brand new suspension all around, yup, everything except tie rod ends. Casual search suggests a) the sky is falling and b) it's likely a blown rack. It does it faintly when the wheels are off the ground, too. I've never seen a rack fail this way in 10yrs of wrenching on cars, fwiw. Maybe a bad steering u joint? TIA. -Cm
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01-31-2019, 08:55 PM	#2
nsjames Brigadier General 2466 Rep 4,328 Posts Drives: 08 328xi Touring Join Date: May 2017 Location: ohio iTrader: (0)	I'd suspect pump before I suspected rack. Pressure relief spring failed? you'd have to get a pressure gauge on things to find out properly.
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01-31-2019, 08:58 PM	#3
nsjames Brigadier General 2466 Rep 4,328 Posts Drives: 08 328xi Touring Join Date: May 2017 Location: ohio iTrader: (0)	also, maybe it's starving for fluid because the filter in the reservoir is plugged?
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02-01-2019, 03:53 PM	#4
Cm452 Private 8 Rep 80 Posts Drives: 08 335XI, stock...for now Join Date: Oct 2018 Location: Boston Metro iTrader: (0)	I'd imagine that if it were starved of fluid it would moan, like most hydraulic pumps when the fluid gets low. As for the pressure test; is there a port that I can tap into, or do I have to jury rig something onto the banjo fittings? Did these cars come with variable ratio/ variable assist? I've got the sport package if that tells you anything... -Cm
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