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Jag-lovers' Ebooks
- Jag-Lovers' xj40 Ebook -

7.1 - Hydraulic System ( )

XJ40 Hydraulics, System Test :

Initial test :

Required equipment:Stopwatch, tape measure, and strong right leg!

Check Ride Leveling Struts :

Measure height at rear fenderwell Run car above idle, check and measure rise Run at idle, check and measure rise, 5/8" is factory recommended maximum. Use 1/2" as a safety standard. Gas bladder in strut is ruptured if rise is excessive. Strut pair needs to be replaced or converted.

Check Accumulator :

Run car at 2000+ RPM for 30 seconds. Shut motor off and turn key on to activate VCM. Pump pedal slowly, 3 count intervals, check the number of times before the low brake pressure warning light comes on. A fully charged accumulator will go 9 pumps. 4 pumps necessitates system check out, probable accumulator bladder failure.

Check Charge Solenoid :

Continue pumping down system after previous test until pedal is rock hard. Start car and stopwatch, run at idle, observe VCM. Stop timer when low brake pressure indicator goes out. A red border can be seen if a different warning is reading on the inner screen. The red border is a background indicator of this warning. Test several times. 9 to 15 seconds is a good reading. Any longer and pump pressure could be low or charge (load) solenoid may not be seating. Common probable fault is the charge solenoid.

Pump, Charge Solenoid, Accumulator Combo Test :

Run car at 2000+ RPM for 30 seconds. Return to idle. Pump brake pedal firmly and swiftly until low brake pressure light comes on. Stop at 30 pumps. Roughly 10 pumps usually signals a faulty charge solenoid (not seating). It is less likely but possible for low pump pressure or a completely discharged accumulator to fail this test. See pump test.

Hydraulic Pump Test :

Disconnect line to valve block. Check pressure. Most failed pumps can be stopped off with thumb pressure. Check flow of ??? per minute???

Check Valve Test :

To check discharge of hydraulic ride leveling system, charge system and measure ride height at fender lip. Recheck height after 12 hours. More than 1/8"??? sag is a sign of a faulty check valve located behind the up solenoid.


7.1.1 - Brake Accumulator Replacement ( )


The replacement of the accumulator on the 3.6 litre XJ40 can be very easy or very difficult - just the luck of the draw. It is absolutely essential to completely depressurise the system before attempting this replacement, as releasing high pressure oil can be very dangerous.

If the entire accumulator assembly is removed from the car, the only hard part is getting the hydraulic connections back on and not cross-threaded. Make a clear note of how far the connections screwed in, to be certain if they are cross threaded or not on replacement before using a spanner. Also, if the clamp around the accumulator (that holds the assembly on the car) is attached but left loose until the connections are almost fully tightened, it can make the job easier.

Another caution is in unscrewing the old accumulator from the aluminium block and screwing on the new one. Using a spanner is not a good idea. It is much better to clamp very lightly in a vice with wood blocks and use a filter wrench. The accumulator does not need to be over tightened. It seals with an 'O' ring and cannot undo when in place.

Some mention has been made of the electrical block connectors. Having fiddled with these on several occasions, they are very simple to dismantle after the first time. The pins each have a small nib that springs outward when the pins are in place and stops them from pushing back. After fishing out the seals from inside the plug, this nib is accessible and can be bent back in with a very small screwdriver or similar. Before re-assembling, it is necessary to bend them back out.


7.1.2 - Accumulator Non Return Valve ( )

The seats for the valves may eventually a number of ridges worn in to them reducing the length of time they hold pressure for. Jaguar don't sell the valve except as part of the switch housing assembly. These ridges can be removed with wet or dry paper, finishing off with 1200grit.

The alloy block that the Accumulator vessel and charge/ pressure switches screw into has two pipes also screwed into it. The top pipe (from the booster) screws straight into the block. The bottom pipe (from the Valve Block) screws into what looks like a 22mm nut. If this is removed a small spring loaded plunger is revealed. This seats against the inner face of the 22mm nut. It was this inner face that needs cleaned up.

You may need to remove the whole assembly and get the block in a vice as the 22mm is quite tight.


7.1.3 - Self-Leveling Suspension ( )

The best answer here is if you have ANY problems, replace them with non-self leveling shocks. Jaguar do a conversion kit, the following is a summary of the Jaguar Technical Bulletin and does not cover removal/ replacement on the car itself.

Having removed the assembly from the car dismantle it and rebuild the new units. I’m assuming any kit will have fairly detailed instructions on this.

Not forgetting to grease everything reassemble and tighten top nut to 23-28 ft-lb.

Remove luggage compartment front trim panel and find the rear axle electrical connector. ( ’92 black 8 way, ‘93 white 8 way connector)

Remove the following wires:


Pin -’92 ‘93

1
brown/ blue
brown/ orange

2
white/ slate
white/ slate

5
yellow/ brown
yellow/ orange

6
yellow/ blue
yellow/ blue


Tape up the wires. DO NOT remove the brake pad sensor wires.

Refit trim.

Jack up vehicle and remove self leveling struts.

Remove hydraulic crossover pipe from clips above rear subframe.

Install new assemblies.

Find valve block, (-’92 on right hand inner wing, ‘93 under front crush tube).

Disconnect rear suspension feed pipe from block.

Plug with bleed screw (part no. CAC 8293) and tighten to 12-14 ft-lb.

Remove feed pipe from body clips.

Start engine and check valve block for leaks.

Jaguar official repair time 2 Hrs.


7.15 - Steering ( )


7.15.1 - Steering Racks ( )

Steering Racks (rebuilt exchange) should take less than 45 minutes to change. Add 15 more minutes to readjust the toe (if you measured the exact distance between tie rod ends and between one tie rod end and a chassis part (to establish the same steering wheel position you had before) prior to removing the old rack and you'll come in at just under an hour.


7.15.2 - Power Steering Leaks ( )



The most likely source of a leak is the hose that feeds the pump. That’s the first thing that goes. There is also an oil passage running to the head that leaks above the pump, and engine oil will dribble down onto the pump.

The power steering pump itself can also leak. The leak typically comes from an O-Ring inside the pump towards the back of the car.

The high pressure line comes from the back of the pump. There is a small O ring on the high pressure line fitting this may be the source but..

The high pressure line is threaded into what looks like a bushing. Be careful when you remove the bushing as a spring loaded piston may pop out. On the "bushing" is another O ring that may leak.

Approx. 30 minutes work.


 

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