Instructions for 4x4 Bypass
One of the most common reasons for the unserviceability of the 4x4 system is a blown pressure plate seal in the transfer box. This failure may be brought on by a number of factors including:
1. Failure to change the accumulator at specified service intervals - A worn out accumulator can't damp out instantaneous pressure surges which instead find the next component that will "give". In this case the pressure seal in the TX box.
2. Running uneven tyre sets (make/tread/pressure) causes stress in many of the transfer box components including the pressure seal. The temperature generated in such conditions weakens the seal further.
3. Turning full lock stresses the transfer box. At low speeds much of this can be taken up by the viscous coupling which acts in a similar way to a limited slip differential. However, accelerating hard when on full lock puts a tremendous strain on the TX box internals and may contribute to seal failure
The last two 4x4 Turbos I have purchased were both sold to me due to this fault by owners panicked by the prospect of heavy repair costs. A blown seal also has knock on effects for the Power Assisted Steering (PAS) as the hydraulic fluid that operates the pressure plate comes the PAS system. Once the seal has failed pressurised fluid enters the transfer box and is inevitably ejected from the transfer box breather pipe. In a matter of seconds both the 4x4 and PAS systems fail. Although the 4x4 system need major attention the PAS system can be reinstated by simply removing a fuse or a couple of relatively simple bypass procedure allowing you car to run in 2WD mode until you have the time and funds to effect a proper repair. The simple instructions to do this can be found below.
Method 1:
This method is the quickest and easiest and should ensure that the PAS fluid remains in the power steering circuit. Basically, all you need to do is remove fuse 19 to prevent the solenoid valve from operating and thus no fluid will be directed to the TX box. You will of course need to fill the PAS reservoir up again to enable the power steering to operate correctly. There is a possibility that there may be some seepage with this method although monitoring the PAS levels will ensure system operability. If this method is used you will have to tolerate the 4x4 light being constantly illuminated.
If you require a more permanent solution or if you wish to remove the accumulator completely then you may want to try one of the solutions below.
Method 2:
This is simplicity itself. Simply remove the hydraulic feed to the TX box at the accumulator end (marked as TX in figure 2 below). Next fit a hydraulic blanking plug to the accumulator. A plug may be obtained from a local hydraulic company or even a plumber's merchants. The system is now sealed and may be topped up and bled (see Method 2 below). With this configuration the 4x4 ECU will not see any problem and assume the 4x4 is fully functional and hence no 4x4 light staring you in the face on every journey.
The only snag with this method is getting hold of the correct sized plug. Not easy when you are stranded at the side of the road in a puddle of PAS fluid. I would advise any Calibra/Cavalier 4x4 owner to source one of these plugs and keep it in the boot.
Method 3:
Tools Required: 13mm socket/spanner, 17mm open end spanner, 22mm open ended spanner, small sockets (5/6/7mm) and extension bar or long flat screwdriver for jubilee clips, cloths to mop up spillage.
The accumulator and 4x4 hydraulic control block can be found against the bulkhead near to the external fuse/relay box. Figure 1 below shows the location of the accumulator block assembly.
Figure 1 - 1993 Calibra 4x4 Turbo with accumulator block in place
For better access to the accumulator block assembly it may be necessary to remove the black plastic "TURBO" plenum cover. This will also make it easier to remove the accumulator block once all pipes and electrics have been disconnected. Figures 2 and 3 show the various connections that need to be removed to complete the accumulator removal process.
P1 and P2 are high pressure hydraulic lines (approx. 800 psi) and you must ensure that these are depressurised before disconnecting. If the pressure seal has failed then this line should not be able to pressurise but as a precaution I suggest you pump the brake 25 times with the ignition on (engine off) to remove any residual accumulator pressure. Needless to say, when undertaking any of the bypass procedure, do so with the engine OFF!!!
NOTE: In an emergency the bypass may be achieved by disconnecting only P1 and P2 from the accumulator block assembly and reconnecting them together. However, when I tried this I was still very gradually losing PAS fluid over a period of time. I suspect that without the pressure side being operational some of the seals may allow slow seepage from the return line through the accumulator block. For full bypass read on...
R1 and R2 are return lines taking PAS fluid back to the PAS reservoir. These have only minimal pressure but again should only be disconnected with the engine off. TX is the pressurised feed to the transfer box pressure plate. E1 is the electrical connection for the pressure switch and E2 (which is below E1 cannot be seen in figures 1 and 2) is the solenoid power signal.
NOTE: The bypass may be achieved by disconnecting only P1 and P2 from the accumulator block assembly and reconnecting them together. This is an ideal solution for getting you home when the seal blows. However, when I tried this I was still very gradually losing PAS fluid over a period of time. I suspect that without the pressure side being operational some of the seals may allow slow seepage from the return line through the accumulator block. For full bypass read on...
Start by disconnecting P1 from the accumulator block with the 17mm spanner. Next disconnect the coupling at P2. This requires a 22mm and 17mm open ended spanner. You can then disconnect TX coupling in the same way as the P2 connection. Next loosen the jubilee clip at R1 and pull the hose from the stub. R2 is slightly more difficult to reach as it's down behind the block assembly. You may need a long screwdriver or socket extension bar to reach it. Once loosened you may find it difficult to pull the hose from underneath the block assembly and it may be better to wait until you have removed the accumulator block assembly from the bracket. Now remove the two bolts that hold the accumulator to the bracket using the 13mm spanner/socket supporting the weight of the accumulator block assembly. Once these have been removed you will be able to manipulate the whole assembly in order to disconnect E1 and E2. You can now also remove R2 if you failed to manage earlier. For some reason R2 seems to be practically welded to the pipe and may take some effort to completely disconnect. Once all connections are free remove the accumulator block assembly from the car.
You can now start the bypass operation. Connect P1 directly to P2 (whether by design or by coincidence these connectors couple together perfectly). You will need to fabricate a pipe to connect R1 and R2. I used a short length of 10mm soft copper pipe with a gentle 90 degree bend (see figure 4) and soldered a compression olive on either end to give the jubilee clip something to grip. As it's not pressurised you may get away with just the pipe.
To prevent the 4x4 light from flashing constantly short out the E1 connections with a pair of spade type crimps and a short length of wire. E2 can be tie-wrapped safely to the vacant accumulator bracket and the plug should be covered with a small plastic bag to prevent the ingress of dirt and moisture.
The TX pipe should be tied out of the way and ideally the open end should be covered with a plastic bag or plugged. Remember, you may well want to reinstate the 4x4 system before too long so take not to damage any of the components.
Finally, fill and bleed the PAS system. This can be done by filling the reservoir and starting the engine. As the PAS pump draws fluid around the system you will need to add more fluid to the reservoir until the correct level is maintained. Once you have bled the system clean all residual fluid from the working area and check for leaks. Replace the PAS reservoir cap and take a short drive to help work the fluid through the system and release any trapped air. After a mile or two recheck the PAS level and top up if necessary. Keep a close eye on the level over the first few days and if it needs constant topping up then recheck the system for leaks.
I can't foresee any major problems with running with this configuration on a long tem basis but I can make no guarantees either. Hopefully you will find the heart (and the money) to restore the car to it's full 4 wheel drive potential and this bypass operation will only be a short to medium term temporary solution. If however you intend to keep in running in this configuration may I suggest you remove the propshaft for an extra saving in terms of both weight and mechanical drag.
If you have any problems or suggestions then please contact me on the ClubCalibra Forum. Good Luck...