Editing HICAS - Removal (section)

=Hicas Removal=

There seems to be a lot of confusion in the various hicas threads with information scattered all over the shop, and I keep getting pm's about it, so I think its about time we put everything in the same place, to stop hicas threads popping up weekly. This is a rough draft, and pics are coming. Feel free to suggest changes, improvements or corrections.


===HICAS, what is it?===
Hicas stands for High Capacity Actively controlled Steering. It is an anti-skid system that was introduced in the HR31 Skyline coupe on its release in 1986 and also in the 4 door hardtop  GTS and Passage models. It is a system designed to steer the rear wheels of the car slightly to prevent the rear skidding while turning (oversteer). It is not a constant  4 wheel system and is designed to move the rear wheels in the same direction as the front, so it doesn't affect the turning circle in any way (parking etc). The HR31 system is completely different to later Nissans and consists of two hydraulic actuators designed to move the entire rear subframe, while S13 etc. is similar to a steering rack, and the subframe/cradle is fixed. (PIC)

===Why remove it?===
HICAS is designed to make the car easier and safer to drive, not faster. The system tends to butt in too early and makes the car unpredictable and uneasy to drive. This is now amplified by the fact that  the HR31 was released over 20 years ago and most are showing their age. The rubber subframe bushes wear out and result in sloppy handling and all sorts of movement, tramping and wobbles in the rear. . HR31's are also very likely to have leaky powersteering systems. Removing the hicas removes most of the steering hydraulics and gives you the opportunity to replace leaky hoses.

==How?==

There are two ways, lockbars and the right way - replacing the bushes.

===Bushes===
The R31 rear subframe is supported at either end by thick rubber bushes. These bushes have hollows in them to allow the subframe to pivot. These need to be replaced. The cheapest solution is to buy aftermarket Z31 rear subframe bushes from the states and have them modified to suit. Noltec also make subframe bushes for HR31. The Z31 bushes will tap in while the noltec items have a steel shell and require a hydraulic press to install.
Urethane is solid stuff, and will remove all measurable movement in the subframe while still isolating vibration from the chassis and maintaining some compliance. It will easily last the life of the car in this situation.
Z31 bush mod: The bushes will fit into the subframe fine, but they are slightly too thick to fit between the chassis and the lower bracket. About 6mm in height needs to be skimmed off the top bush on a lathe.

http://www.noltecsuspension.com/popproduct.php?id=N92962&vhcid=536&brand=NISSAN&series=SKYLINE+R31++++87-90

http://www.thezstore.com/page/TZS/PROD/PSDC06D/23-4148

===Lockbars, why not?===
Lockbars are used for S13, R32/33 etc. why not for a HR31. For starters the system is completely different. The later model Nissans have a hicas rack (similar to a steering rack) that is attached to the subframe and pivots the rear wheels. This is replaced with a single lockbar, locking the wheels to the subframe, which is still bushed to the chassis. On a HR31, by replacing the rams with lockbars, you are locking the subframe to the chassis and eliminating ALL movement and compliance, and the subframe is not supported at the chassis pins as intended. The subframe is restrained laterally, but the sloppy up/down movement of the subframe with worn stock bushes remains. The result, all sideways rear suspension load is transferred to the actuator mounts, which will eventually lead to hammered out elongated bolt holes and distorted brackets, and you will then need to fit the bushes! do it once, do it right.

===How much? hard to do?===
The Z31 bushes from the states work out at approx $100 delivered, Noltec are 200ish. An aus spec pump and reservoir should be less than $50 from a wreckers.
Doing all the work yourself is inexpensive, but very time consuming, its a big job. The subframe needs to be removed and the ps lines in the engine bay are also tricky to remove with the engine in.



==Down To Business==

===Tools Required===
Nothing too fancy, 1/2" drive socket set, ring spanners, long breaker bar (a must!) and a chunky flat head screwdriver.
If required a set of bullnose pliers for handbrake cable clips and a 10mm flare nut spanner for brake lines can be handy.
The car will need to be put up on chassis stands

===Subframe Removal===
There are a few ways to go about this, but it is possible to remove the subframe on its own with the diff and trailing arms staying supported on jack stands. This is the quickest way to go about it, as the rear brakes, handbrake, tailshaft and driveshafts can stay connected.
When you remove the subframe, there is a large washer on each chassis pin. Remove this, cut off the rubber moulding, clean up, paint and refit.

===Bush Removal===
Remove the centre of the bush using a coping saw, or hack it out with a drill. Once this is removed, carefully cut through the outer shell of the bush with a hacksaw. Once you are through, the shell can be popped out with a screwdriver. Install your new bushes

===PS Pump and Reservoir===
Two options here, keep your import pump and reservoir, or fit an aus spec PS pump and res.
Import pump - this is a two chamber pump, The front is for your steering rack, rear for hicas. You can remove the vanes from the rear pump by taking the rear casing off the pump. The vanes (10 little steel squares) will just drop out.Remove the rear banjo bolt, you can turn it into a plug by filling with solder, then cut a short length of 3/4" copper pipe to replace the banjo fitting, The rear chamber has a bypass valve so blocking it shouldn't cause any issues. You could also just weld up the threaded fitting on the pump to seal it.
Import reservoir - this has two return lines, plug one with a 3/8" radiator stopper or similar rubber bung.

Aus pump - to bolt to an RB20 you need the aus pump bracket. The two lower mounts bolt on but you will need to add a spacer at the top between the bracket and block, use a few M10 washers or similar. Exhaust manifold yokes work as well. The aus pump uses a 3 rib belt while the import is 4. A 3 rib belt will be fine on the 4 rib harmonic balancer. You need a belt 855 or 860 long (3PK855 etc)
Aus reservoir - bolts straight up to the strut tower.
Note: the pump supply hose is a different size between import and aus, so you need to use aus pump + res, or import pump + res, not a combination.

===Steering Rack===
The easiest thing to do here is keep your import KYB hicas rack. It has a quick ratio at 2.5 turns lock to lock (Aus is 3.25). R32/33 rack can be used but will require custom lines. The import rack will also accept R32 tie rods if you wish to do the S13 coilover conversion.
Import rack mod - easy. On the rear of the rack body there is a valve with four lines going into it. Two lines go towards the back of the car, and one pressure line from the hicas solenoid, and a return to the reservoir. Disconnect these and seal the ports to stop leaks and dirt getting in. Automotive power steering threads are unique and its not possible to buy plugs, so make your own out of the discarded lines. Cut the end off leaving about an inch of steel line sticking out, flatten it in a vice and fold it on itself to seal, done (PIC)

===Actuators, Lines and Solenoid Valve===
The actuators at the rear, their brackets and all the hydraulic lines that run forward to the steering rack can be removed. The supply line from the pump (rear chamber), the hicas solenoid valve/controller and the return lines from this unit and the rack can go. You will be left with a single high pressure line from the pump to the rack, and a single return to the reservoir. Once the rear lines and actuators are out, reinstall the rear end.



==Other info==

===HICAS light?===

Removing the hicas will not result in your hicas light coming on. The light is turned on by the level sensor in the fluid reservoir and will come on when your ps fluid is low. If you fit an aussie reservoir then the sensor is removed.