Jaguar XJ40 Power Steering Problems, Steering Rack
On the XJ40 most power steering trouble is fluid and hoses before it is the rack: check the level and the right fluid for your year first, then hunt leaks under load and see whether the rack moves in its mounts. A new rack is the last step, and it has to match the model year.
How bad is it · Garage, carefully
Drivable with care, unless the rack is loose
Losing assistance makes the car heavy to steer, not uncontrollable, but a pump run dry gets damaged. A rack with missing mounting bolts can let go, so fix that before driving on.
Which one applies to yours depends on your symptoms, your model year and what has already been done to it.
Likely causes, most common first
Read the check cost before the odds: a free check that rules a cause out beats a likely guess that costs money.
Low, old or wrong fluid
The XJ40 takes two different fluids depending on the year. Cars from 1988–89 and 1993–94 have a separate black reservoir with Dexron ATF; on 1990–92 self-levelling cars the steering draws from the same reservoir as the power hydraulics and takes green mineral oil. Low or tired fluid lets the pump cavitate and the rack lose pressure.
A whine or coarse whirr on full lock and when parking, a groan with some shake in the wheel, or assistance that comes and goes from one side to the other. There is no pump belt on this car, so a whine is not a slipping belt — more often a reservoir almost empty.
Check the dipstick in the cap cold, after the car has stood overnight, and fill only to the mark; a hot check overfills and it spews out later. Note the colour: dark and thin means change it.
Top up or drain and refill with the fluid your year needs; on a shared mineral-oil reservoir never pour in ATF while self-levelling is still live. The whine usually goes on the first drive. If the level keeps dropping, look at the reservoir cap gasket as well, and don't over-tighten an old plastic cap.
Leaking hose, union or reservoir nipple
The pressure hose leaks at its crimped end about a foot short of the rack, hidden under a sleeve, and only when the rack is under load, so it soaks the rack and looks like a rack leak. Return hoses, the cooler unions in the radiator, the T-joint clamped to the frame and the brittle reservoir nipples all weep too.
Fluid low at the front of the engine or over the rack, often worst after hard turning at parking speed.
Clean everything, then have someone turn the wheel lock to lock with the engine running while you watch the crimps and unions. The pressure hose on right-hand drive cars is CCC7568; MMD3984AA is the left-hand drive one. A leak from above the subframe is a hose, not the rack. Look too at the low-pressure hose from the reservoir to the pump near the exhaust — it hardens and weeps.
Renew the leaking hose; to reach the pressure union at the rack, undo one of the other union nuts first. If new rack fittings weep at full lock, fit fresh O-rings and work the pipes back and forth to seat them before tightening. The pressure hose can also be made up by a hydraulic hose shop: it is standard 3/8 in two-wire high-pressure hose with serviceable couplings.
Rack leaking at its own seals
The outer seals let fluid into the gaiters and out at the tie rods; the valve seals under the plate at the top of the pinion leak where the column joins. A worn bore makes a merely resealed rack leak again, and exchange racks are not always better than a sound original.
Fluid at the tie-rod ends or the pinion top, wet gaiters, a leak that shows only while the wheel is turned.
Pull back a gaiter: gear oil there is normal, power steering fluid means an outer seal. Also look for a missing threaded plug in the pinion tower, the rack centring hole. A heavy leak only on lock points at the rod seals: squeeze the gaiters to feel whether they are full of fluid.
Valve and pinion seals are kit JLM10839, rack seals JLM10838; a seal kit plus a little treatment can keep a good rack dry. A missing centring plug takes an 8 mm x 1.0 bolt. If an exchange rack leaks, moving its new tie rods onto your original rack is worth doing.
Rack loose in its mounts
The rubber bonding in the rack mounts perishes and lets the rack slide sideways, about 1/2 in at the wheel. Missing or loose mounting bolts do the same, only worse. The four rack bolts work loose too: with three loose, the fourth can slide in its slot at the apex of a turn, and with them gone the steering barely responds and then over-reacts.
Vague, wandering steering, rut following, a thump on full lock, and play at the wheel with the car standing.
Engine off, wheels on the ground: rock the wheel and watch the rack body against its brackets. Count the four 13 mm bolts from below.
Replace missing bolts first. Pack the gap at the mount flanges with tightly wound wire, springs or nylon cord, or fit spacers; a badly worn rack is better re-bushed by a rebuilder. The difference in steering response is immediate. Two new bolts with lock nuts on a car whose rack bolts had gone made the steering 'almost perfect'. Bolts that keep loosening take jam nuts.
Stiff or one-sided when cold
On early racks the nylon rings in the aluminium head wear into the bore and only seal once warm. From about 1990 the factory fitted a revised Adwest rack: a harder head and rings with a metal expander behind them.
Heavy steering, or no help on one lock, on a cold morning that clears after a few turns lock to lock or a few minutes of running.
If the fluid was never low and it frees up once warm, the rack is the suspect, not the pump. Check the level first: one car that was stiff when cold got far worse as the reservoir ran nearly dry. Flushing to fresh fluid sometimes frees seals that stick for the first minute or two.
A power steering additive at about 5% cured it on a car with a separate ATF reservoir. On a shared mineral-oil reservoir feeding self-levelling, skip additives; the lasting cure is a later or a ZF rack.
Wrong rack for the year after a swap
From 1993 model year the rack pinion is tilted 10.5 degrees, and the 1994 ZF rack has a taller pinion with its lock-bolt groove about 3 mm lower. On an earlier car the column universal joint is then forced to a bad angle and binds.
After a rack change the steering binds or goes tight over part of a turn, the universal joint looks strained, or the steering stays notchy and heavy.
Compare part numbers and pinion height with the old rack before fitting; V12 cars also use different mounting brackets, and ZF and Adwest racks are not interchangeable without changes.
Shims the thickness of a 10 mm washer under each rear rack bolt can cure the binding; otherwise grind the pinion groove about 3 mm higher and slide the spline clamp 10–15 mm along. Note where the pinch-bolt cut-out sits, or the wheel ends up 150 degrees off. If the wheel sits off centre afterwards, the track rods were set unequal: lock the rack centre with a drill bit in its tooling hole, set the toe equally on both sides, then refit the wheel straight on its spline.
Heavy at parking speed on the earlier rack
The 1993–94 rack has a larger piston and the revised angle, so it is noticeably lighter than the 1988–92 one. Wrong toe on any rack also makes steering heavy.
Heavy when parking compared with a later XJ40, yet no noise, no leak and normal on the move.
Have the alignment checked first; heavy steering on an otherwise healthy rack is often just wrong toe.
A 1994 ZF rack swapped into a 1992 car with new track rod ends gave a noticeable gain at low speed; toe has to be reset afterwards.
Dry gaiters or a tight adjuster on a new rack
The rack arms are not oiled by the power steering fluid. Each gaiter should carry 0.19 L of gear oil, and new racks often arrive dry. A rebuilt rack can also leave the adjuster set tight.
Steering clearly stiffer straight after a new rack went in, with good tracking and no leaks; sometimes a moan from the rack.
Pop a gaiter clamp and look for oil inside. On 1990-on racks the adjuster is a hex screw inside a large lock nut.
Fill each gaiter with 0.19 L of 80W-90 hypoid gear oil, not ATF. If still tight, back the adjuster off a little after marking its position; many new racks also loosen up in a week or two.
Pump shaft seal or a wrongly rebuilt pump
The XJ40 pump is driven from the back of the timing cover, not by a belt. Its outboard shaft seal can leak into the drive adaptor, and a pump rebuilt in the wrong order makes flow but no pressure. With fluid in the reservoir and no assist at all, the pump drive itself can have sheared, or the rack is passing fluid straight back to the return.
Fluid dripping from the breather hole of the pump adaptor, or no assistance at all with fluid circulating normally. A shaft seal leak drains from the witness hole in the adaptor onto the exhaust and the right-hand suspension.
Confirm a noisy pump with a stethoscope before taking it out; hoses perish far more often than the pump itself.
Reseal kit AEU2787 cures the shaft seal leak; the drive dog must go back in exactly the same position. If a blocked outlet valve stops assistance, clean it and refit the spring first with the flat face of the valve to the rear. Measure the depth of the drive dog before taking the pump off, so it goes back the same.
Self-levelling hydraulics leaking into the shared reservoir
On 1990–92 cars the engine-driven power hydraulics pump and valve block share the reservoir with the steering. They leak with age and spread oil over the engine bay, and the steering takes the blame.
Light brown oil behind the right front of the car, an oily belt area, a reservoir that never stays full, a rear that no longer rises at start-up.
Trace the hoses from the reservoir: a third spigot and a pump on the timing cover mean the power hydraulics are still there.
Remove the hydraulics pump and valve block, blank the timing cover (plate EAC3977, hose CBC6297 to the steering pump, screws FS108201J shortened), then a two-spigot reservoir CCC2789 is enough. The rear springs must change at the same time. On a V12 the self-levelling runs off the steering pump, so only the rear line can be capped.
Play elsewhere — the column joint, tie rods or subframe mounts
Not all steering slop is in the rack. The universal joint in the column can bind or wear, the tie rods wear, and split rear mounts on the front subframe let the whole front end shift.
Steering that sticks at the centre, vague in curves or wandering, while the rack is tight in its mounts and dry.
Unbolt the column from the rack and feel the universal joint move freely in every direction. With the wheels off the ground, hold each at 9 and 3 o'clock and rock it for tie rod play, and look at the subframe rear mounts for splits.
Renew the column joint or the worn tie rods, and the subframe mounts if split; one car stopped sticking at the centre with a new column joint.
Stiff only when hot — a collapsing hose or the rack valve
Old hoses can break down inside and bulge or collapse when hot, restricting flow. Debris or a weak control spring in the rack's valve body does the same.
Steering normal from cold and getting heavier as the system warms, with the level correct.
Have the system pressure-tested cold and hot. Look for a hose that swells or goes soft when hot, and on self-levelling cars for a blocked in-line filter.
Replace the tired hoses first; cleaning the control valve body is the next step before a new rack.
The order to check them in
The point of the order is money: each step either rules a cause out or makes the next one worth doing. Green is free, amber costs a little, red is the one to arrive at last.
Fluid level and type
Cold, after standing overnight, read the dipstick in the cap. Find out which fluid your year takes before topping up: ATF on separate reservoirs, mineral oil on the shared one.
freeTyre pressures and alignment
Chatter, kickback and a nervous feel can be nothing but over-inflated front tyres: for example, 40 psi set where 28 front and 30 rear were due. Wrong toe makes steering heavy or wandering.
freeWatch the rack in its mounts
With someone rocking the wheel, see whether the rack body moves against its brackets, and check all four mounting bolts are there. A missing rack bolt is a stop-driving fault.
freeFind the leak under load
Clean the hoses, unions, reservoir and rack, then turn lock to lock with the engine running. Look at the pressure hose crimp before blaming the rack.
freeBleed after any work
Front wheels off the ground, engine running, turn lock to lock a few times, up to about 25, keeping the reservoir topped up. Foam clears and the grating noise goes.
freeReseal or exchange the rack
Match the rack to the model year, fill the gaiters with gear oil, count tie-rod turns to keep toe, and lock the rack centre with a drill shank in its centring hole. Have the alignment done afterwards.
seal kit, or an exchange rack plus alignmentWhat it usually isn't
Don't spend money here first:
If none of this finds it:
On jagaux.com
- Jaguar XJ40 Rear Suspension ProblemsIf you take out the self-levelling hydraulics, the rear springs have to change too.
- Jaguar XJ40 ABS and Brake Accumulator ProblemsGreen mineral oil and the engine-driven hydraulic pump also feed the brake assist on the earlier cars.
- Jaguar XJ40 Front Suspension Knock, Worn BushesA clunk over bumps rather than through the wheel is usually the front suspension bushes.
- Jaguar XJ40 Steering Wheel ShakeIf the steering wheel shimmies at speed or wobbles under braking.
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